Alison Kyra Carter

Sarah Klassen

Miriam T Stark

Martin Polkinghorne

Piphal Heng

Damian Evans

Rachna Chhay

The evolution of agro-urbanism: A case study from Angkor, Cambodia

Keywords: Urbanism, Agro-urbanism, Demography, Cambodia, Angkor, Southeast Asia

The vast agro-urban settlements that developed in the humid tropics of Mesoamerica and Asia contained both elite civic-ceremonial spaces and sprawling metropolitan areas. Recent studies have suggested that both local autonomy and elite policies facilitated the development of these settlements; however, studies have been limited by a lack of detail in considering how, when, and why these factors contributed to the evolution of these sites. In this paper, we use a fine-grained diachronic analysis of Angkor's landscape to identify both the state-level policies and infrastructure and bottom-up organization that spurred the growth of Angkor as the world's most extensive preindustrial settlement complex. This degree of diachronic detail is unique for the ancient world. We observe that Angkor's low-density metropolitan area and higher-density civic-ceremonial center grew at different rates and independently of one another. While local historical factors contributed to these developments, we argue that future comparative studies might identify similar patterns.

Introduction

In recent years, comparative archaeological studies of urbanism have increasingly focused on agrourban centers, which are sometimes called distributed urban network systems or garden cities (e.g., [START_REF] Chase | Urbanism and anthropogenic landscapes[END_REF][START_REF] Fisher | The role of infield agriculture in Maya cities[END_REF][START_REF] Fletcher | Low-density, agrarian-based urbanism: A comparative view[END_REF][START_REF] Fletcher | Low-density, agrarian-based urbanism: Scale, power and ecology[END_REF][START_REF] Graham | Maya cities and the character of a tropical urbanism[END_REF][START_REF] Graham | Neotropical cities as agro-urban landscapes: Revisiting 'Low-density, agrarian-based urbanism[END_REF][START_REF] Isendahl | Agro-urban landscapes: the example of Maya lowland cities[END_REF][START_REF] Lucero | From 'Collapse' to urban diaspora: the transformation of low-density, dispersed agrarian urbanism[END_REF][START_REF] Scarborough | Distributed urban network systems in the tropical archaeological record: Toward a model for urban sustainability in the era of climate change[END_REF]. This type of low-density urbanism is not uncommon in the archaeological record of the tropical world, and is categorically different from the compact, high-density cities of Mesopotamia and other classical civilizations that have provided the archetypes for understanding urbanism (e.g., [START_REF] Coningham | The state of theocracy: defining an early medieval hinterland in Sri Lanka[END_REF][START_REF] Isendahl | Sustainable agrarian urbanism: The low-density cities of the Mayas and Aztecs[END_REF][START_REF] Kusimba | Precolonial African cities: Size and density[END_REF]. Agro-urban spaces have relatively low population densities in the metropolitan zones that typically sprawl far beyond the higher-density regal-ritual or civicceremonial monumental centers. The boundary between these two spaces is frequently blurred [START_REF] Fletcher | Low-density, agrarian-based urbanism: Scale, power and ecology[END_REF]. Civic-ceremonial centers often have extensive green spaces, such as household-level gardens and larger areas like parks (Stark, 2014a;Stark, 2014b). This integration of agricultural land within urban environments appears to have made agro-urban settlements flexible and sustainable [START_REF] Isendahl | Sustainable agrarian urbanism: The low-density cities of the Mayas and Aztecs[END_REF][START_REF] Scarborough | Distributed urban network systems in the tropical archaeological record: Toward a model for urban sustainability in the era of climate change[END_REF].

While recent work has considered the decline of agro-urban centers [START_REF] Lucero | From 'Collapse' to urban diaspora: the transformation of low-density, dispersed agrarian urbanism[END_REF][START_REF] Gilliland | The dry tank: Development and disuse of water management infrastructure in the Anuradhapura Hinterland, Sri Lanka[END_REF]Fletcher 2009: 15), there has been comparatively little effort devoted to understanding how these massive settlements formed and grew. In this paper, we draw on multiple datasets including lidar, archaeological excavation data, radio-carbon dates, and machine learning algorithms to map the development of one of the world's largest preindustrial agro-urban settlements: Angkor, in present-day Cambodia [START_REF] Evans | A comprehensive archaeological map of the world's largest preindustrial settlement complex at Angkor, Cambodia[END_REF]. Angkor was the preeminent regional power from the 9-15th centuries CE, controlling a large portion of mainland Southeast Asia. Our work suggests that Angkor's initial population in the 9th century likely was approximately 160,000-250,000 people and grew to between 688,000-900,000 people at its apogee in the 12-13th centuries CE (Klassen et al., 2021). We argue that Angkor's higher-density civic-ceremonial center (henceforth CCC), dispersed rural metropolitan area (henceforth AMA) and its embankments (henceforth BANKs) grew at different rates, and that this growth was facilitated by both top-down infrastructure development as well as bottom-up organization. In the following section we contextualize our work within broader studies of agro-urban settlements, before moving to provide a background on Angkor and our methods, and finally offering a detailed discussion of historical and demographic developments at Angkor over time.

Agro-urbanism in the archaeological record

Agro-urban settlement complexes are distinctive and important urban morphologies that are found in both the ancient and contemporary world. Despite the increased attention paid to agro-urban centers in recent scholarship, understanding the conditions and structures that allowed for the emergence and development of these settlements is still in the early stages [START_REF] Fletcher | Trajectories to low-density settlements past and present: paradox and outcomes[END_REF]. Fletcher and others have proposed that extensive, low-density urban forms emerged from high-density cities that continued expanding [START_REF] Fletcher | The Limits of Settlement Growth: A Theoretical Outline[END_REF]Chapman and Gaydarska, 2016a). Other recent work has identified different developmental trajectories based on the areal extent of the settlements [START_REF] Fletcher | Tropical environments and trajectories to low-density settlement forms[END_REF]; in this model, smaller (1-100 km2) settlements tend to expand out of smaller villages. Several scholars have noted that these sites were egalitarian or heterarchical in their organization, with bottom-up or local organization as the driving force behind their trajectory of growth (Chapman and Gaydarska, 2016b;[START_REF] Mcintosh | Floodplains and the development of complex society: Comparative perspectives from the West African Semi-arid Tropics[END_REF][START_REF] Mcintosh | Early urban configurations on the Middle Niger: Clustered cities and landscapes of power[END_REF][START_REF] Moore | Beyond iron age 'Towns': Examining Oppida as examples of low-density urbanism[END_REF].

In contrast, the vast agro-urban settlements (over 100 km2) that developed in the humid tropics of Mesoamerica and Asia had a different type of organization. These settlements contained large communal ritual spaces, monumental architecture, and hydrological infrastructure that integrated rural spaces and civic-ceremonial centers [START_REF] Fletcher | Tropical environments and trajectories to low-density settlement forms[END_REF][START_REF] Lucero | From 'Collapse' to urban diaspora: the transformation of low-density, dispersed agrarian urbanism[END_REF]. The sociopolitical organization of these cities was unequivocally hierarchical, yet we see variability in the role of elite power, state control, and centralized planning as drivers for the development of these sprawling settlement complexes. For example, at the Maya site of Caracol in Belize, it appears that the development of causeways connecting three distinct settlements catalyzed their growth and eventual coalescence into a single settlement. Over time, the epicenter at Caracol was rebuilt and expanded and continued to integrate administrative and market areas through transportation infrastructure. Agricultural fields and heterogeneous residences were also incorporated into this landscape [START_REF] Chase | Urbanism and anthropogenic landscapes[END_REF]. While this might suggest that elite planning and organization facilitated the growth of the city, recent work has identified that bottom-up construction and management of water reservoirs was also key to the successful expansion and agricultural productivity of this settlement [START_REF] Chase | Beyond elite control: residential reservoirs at Caracol, Belize[END_REF]. Similar studies at other Maya sites suggest households in those locations had even more autonomy in managing their infield agricultural systems, thereby shaping the organization of their settlement landscapes (Fisher,2014).

The site of Anuradhapura, Sri Lanka, shows a different mix of centralized and decentralized autonomy in the formation of its extensive settlement complex. There the hinterland was integrated with the civic-ceremonial center by way of a network of Buddhist monasteries that held considerable economic power [START_REF] Strickland | Hydraulic complexities: Collapse and resilience in Sri Lanka[END_REF]. The growth of Anuradhapura and its extended hydraulic infrastructure began prior to the development of the monastic system, but expanded considerably as the monastic system grew. Anuradhapura's expansion seems to have been facilitated by both statelevel construction of large water storage tanks and complex canal systems, as well as more localized hydraulic infrastructure overseen by the Buddhist monasteries [START_REF] Gilliland | The dry tank: Development and disuse of water management infrastructure in the Anuradhapura Hinterland, Sri Lanka[END_REF][START_REF] Strickland | Hydraulic complexities: Collapse and resilience in Sri Lanka[END_REF]. The relationship between the secular rulership and powerful Buddhist communities in the hinterland shaped the formation of this urban center.

These studies raise intriguing questions about the conditions and structures that contribute to the development of extended settlement complexes; frequently, however, the absence of fine-grained detail impedes our ability to fully understand the complex processes at work across multiple scales of time and space, and this has certainly been true of Angkor itself. In this paper, therefore, our aim is to draw together several decades of multidisciplinary research results to model Angkor's spatiotemporal development in granular detail, in order to inform a discussion of the emergence and growth of the settlement complex overtime (Fig. 1). Angkor is unusual in its archaeological coverage: over the last thirty years, more than 3000 km2 of the Greater Angkor Region has been mapped by archaeologists, by hand, in exceptional detail and then followed up with comprehensive ground verification [START_REF] Chevance | Mahendraparvata: an early Angkor-period capital defined through airborne laser scanning at Phnom Kulen[END_REF][START_REF] Evans | Putting Angkor on the map: a new survey of a Khmer 'Hydraulic City' in historical and theoretical context[END_REF][START_REF] Evans | Airborne laser scanning as a method for exploring long-term socioecological dynamics in Cambodia[END_REF][START_REF] Evans | Uncovering archaeological landscapes at Angkor using lidar[END_REF][START_REF] Gaucher | Angkor Thom, une utopie réalisée? Structuration de l'espace et modèle indien d'urbanisme dans le Cambodge ancien[END_REF]Pottier,1999) (Fig. 1). Recent work combining geographic information systems analyses and machine learning algorithms has enabled temples and other features on the landscape to be dated [START_REF] Klassen | Top-down and bottom-up water management: A diachronic model of changing water management strategies at Angkor, Cambodia[END_REF][START_REF] Klassen | Semi-supervised machine learning approaches for predicting the chronology of archaeological sites: A case study of temples from medieval Angkor, Cambodia[END_REF] and has provided models of population growth and decline (Klassen et al., 2021). This extensive and unusual dataset allows us to begin creating finer-grained models for the development of the settlement complex of Angkor over time.

Angkor's landscape and temples

The empire's capital and heartland, the Greater Angkor Region, lies on a lowland plain on the eastern edge of the floodplain of the Tonle Sap Lake. As we define it for the current study, the Greater Angkor Region encompasses approximately 3000 km2, reaching from the Tonle Sap into the Kulen hills (Fig. 1). This boundary is somewhat arbitrary and partially based on the watershed catchment boundaries of Angkor's rivers and the original Zoning and Environmental Management Plan for Angkor (ZEMP) established in the early 1990s as part of Angkor's UNESCO World Heritage listing [START_REF] Evans | Putting Angkor on the map: a new survey of a Khmer 'Hydraulic City' in historical and theoretical context[END_REF][START_REF] Wager | Developing a strategy for the Angkor world heritage site[END_REF]. The extent of settlement beyond these boundaries is the subject of ongoing research, but it is clear that the low-density distribution of local temples extends in a wide arc across modern-day Cambodia. The monumental or CCC zone, containing the massive stone temples for which Angkor is famous, encompasses approximately 30 km2 (Fig. 2)1 .

Conventionally, the Angkor period is considered to have begun with the ruler Jayavarman II (r. 770-830 CE), who established himself as universal monarch in 802 CE, and ended in 1431 CE with the supposed sacking of Angkor by the rival kingdom of Ayutthaya located in present-day Thailand [START_REF] Briggs | The Ancient Khmer Empire[END_REF][START_REF] Coedès | The Indianized States of Southeast Asia[END_REF]. These simplified narratives gloss over a great deal of historical complexity. Sedentary agricultural communities have been living on the eastern edge of the Tonle Sap floodplain since at least 1000 BCE (Pottier, 2006b;[START_REF] Pottier | Koh Ta Meas, un site préhistorique dans le Baray Occidental Rapport Préliminaire[END_REF]. Numerous inscriptions dating from the 6-8th centuries CE, along with the remains of brick temples, attest to the presence in this region of a significant population ruled by powerful elites throughout the Pre-Angkor period (6-8th centuries CE) [START_REF] Pottier | Nouvelles données sur les premières cités angkoriennes[END_REF]. Furthermore, there is no evidence for a sudden or violent downfall at the end of the Angkor period in the 15th century CE. On the contrary, recent archaeological and environmental studies have pointed towards a gradual demographic decline beginning in the late 13th century CE, driven in part by a series of climatic changes that heavily disrupted Angkor's water management system [START_REF] Buckley | Climate as a contributing factor in the demise of Angkor, Cambodia[END_REF][START_REF] Buckley | Monsoon extremes and society over the past millennium on mainland Southeast Asia[END_REF][START_REF] Hall | An integrated palaeoenvironmental record of Early Modern occupancy and land use within Angkor Thom[END_REF][START_REF] Penny | Geoarchaeological evidence from Angkor, Cambodia, reveals a gradual decline rather than a catastrophic 15th-century collapse[END_REF]. Additionally, expanding trade opportunities, especially with China seems to have been an important "pull-factor" drawing people further south near the modern capital of Phnom Penh to take advantage of these economic opportunities [START_REF] Polkinghorne | Reconfiguring kingdoms: The end of Angkor and the emergence of Early Modern period Cambodia[END_REF][START_REF] Vickery | Cambodia after Angkor, the Chronicular Evidence for the fourteenth to sixteenth centuries[END_REF][START_REF] Vickery | Cambodia and its neighbours in the 15th century[END_REF][START_REF] Polkinghorne | Early Modern Cambodia and Archaeology at Longvek[END_REF]. Insights about Angkor's political organization can be gleaned somewhat from inscriptions, which describe a powerful king at the top of a hierarchy that included many bureaucrats, elite families and relatives, as well as religious specialists, craftsmen, servants, farmers and slaves [START_REF] Lustig | A view of Angkor's economy[END_REF][START_REF] Lustig | New Insights into "les Interminables Listes Nominative d'Esclaves" from Numerical Analyses of the Personnel in Angkorian Inscriptions[END_REF][START_REF] Sedov | Angkor: Society and state[END_REF]. Kings would give or authorize the purchase of land, which in turn was frequently used to establish temples. In practice, the power of Angkorian kings has been described as cyclical; waxing and waning over time [START_REF] Lustig | Using inscription data to investigate power in Angkor's empire[END_REF][START_REF] Sahai | Territorial administration in ancient Cambodia[END_REF]Stark, 2006a). Particular rulers seem to have been more effective at consolidating and expanding the empire than others with the power of regional elites shifting similarly [START_REF] Lustig | Using inscription data to investigate power in Angkor's empire[END_REF][START_REF] Lustig | Losing ground: Decline of Angkor's middle-level officials[END_REF]).

Angkor's agro-urban landscape grew incrementally over time, driven in part by the state construction projects of Angkorian kings who implemented major public works, including the construction of large water storage tanks or baray and the raising of massive stone temples (Table 1). These acts would transform the landscape and allocate (or reallocate) resources, since each temple would need many workers and associated support staff [START_REF] Groslier | VII. La cité hydraulique angkorienne: exploitation ou surexploitation du sol?[END_REF]Pottier, 2000b). To track these developments over time and space, we divide Angkor's landscape into three categories-the civic-ceremonial center or CCC, the metropolitan area or AMA, and the embankments or BANKs-as well as five periods that represent developments in the CCC by some of Angkor's major kings (Table 1 and Fig. 2).

The AMA was an anthropogenic landscape [START_REF] Chase | Urbanism and anthropogenic landscapes[END_REF] dominated by rice fields [START_REF] Hawken | Designs of kings and farmers: Landscape systems of the greater Angkor urban complex[END_REF][START_REF] Hawken | Angkor's Agrarian Economy: A Socio-Ecological Mosaic[END_REF], earthen occupation mounds, and small community temples. This Angkorian settlement pattern is similar to those found throughout the Lower Mekong Basin, from the Khorat Plateau [START_REF] Evans | Sites, survey, and ceramics: Settlement patterns of the first to ninth centuries CE in the Upper Mun River Valley, northeast Thailand[END_REF] to the Mekong Delta (Stark 2006b;[START_REF] Stark | Residential patterning at Angkor Wat[END_REF]. In previous publications, we have referred to this zone as Angkor's hinterland (e.g., [START_REF] Carter | Urbanism and Residential Patterning in Angkor[END_REF][START_REF] Evans | Uncovering archaeological landscapes at Angkor using lidar[END_REF][START_REF] Klassen | Semi-supervised machine learning approaches for predicting the chronology of archaeological sites: A case study of temples from medieval Angkor, Cambodia[END_REF]. However, in other archaeological studies around the world, the term hinterland has often referred to a remote zone outside the core's administrative control (e.g., [START_REF] Kepecs | Chichen itza and its hinterland: A worldsystems perspective[END_REF]Smith, 2014b). The area under consideration here was not peripheral but distinctly integrated into Angkor's CCC through hydraulic and transportation infrastructure (BANKs) as well as a ritual temple-economy (Fletcher et al., 2008a;Fletcher et al., 2008b;[START_REF] Hendrickson | Historic routes to Angkor: Development of the Khmer Road System (Ninth to Thirteenth Centuries AD) in Mainland Southeast Asia[END_REF][START_REF] Sedov | On the problem of the economic system in Angkor Cambodia in the IXXII centuries. Narody Asii i Afriki[END_REF]. For this reason, we use the term metropolitan area to describe the almost 3000 km2 zone surrounding the CCC as it is part of Angkor's urban form, not detached or separate from it as the term hinterland might imply.

AMA community temples have a particular configuration known as prasat-trapeang (temple-pond) (see discussion in Klassen and Evans 2020) (Fig. 3). AMA temples were frequently constructed of perishable materials, most have not been investigated archaeologically, and few have associated inscriptions. However, recent studies have combined multiple lines of evidence with statistical techniques to predict the construction dates of over 1000 of these temples in Angkor's AMA [START_REF] Klassen | Top-down and bottom-up water management: A diachronic model of changing water management strategies at Angkor, Cambodia[END_REF][START_REF] Klassen | Semi-supervised machine learning approaches for predicting the chronology of archaeological sites: A case study of temples from medieval Angkor, Cambodia[END_REF]. In the Angkorian period, temples were the center of social and ritual life, and their affiliation with elites and royalty also made them an important part of the political economy [START_REF] Lustig | Losing ground: Decline of Angkor's middle-level officials[END_REF][START_REF] Sedov | On the problem of the economic system in Angkor Cambodia in the IXXII centuries. Narody Asii i Afriki[END_REF][START_REF] Sedov | Angkor: Society and state[END_REF]. Although land ownership changed over time (see Lustig and Lustig, 2019, and discussion below), temples in the AMA frequently owned or controlled agricultural land and were central to the expansion of Angkorian agrarian economy [START_REF] Sedov | On the problem of the economic system in Angkor Cambodia in the IXXII centuries. Narody Asii i Afriki[END_REF]. Temples also marshalled many lower-status community members' labor. These individuals are frequently listed in large numbers in inscriptions [START_REF] Lustig | New Insights into "les Interminables Listes Nominative d'Esclaves" from Numerical Analyses of the Personnel in Angkorian Inscriptions[END_REF][START_REF] Lustig | Following the non-money trail: Reconciling some Angkorian Temple Accounts[END_REF], where they are often described as unfree or slaves (see further discussion below). In some cases, labor was provided by cyclical workgroups through a fortnight or seasonal calendar [START_REF] Lustig | Following the non-money trail: Reconciling some Angkorian Temple Accounts[END_REF][START_REF] Sahai | The Hindu Temples in South East Asia: Their Role in Social Economic and Political Formations[END_REF][START_REF] Stark | Residential patterning at Angkor Wat[END_REF].

Villages in the AMA were also tied to larger "central temples" in the AMA to which they provided goods and labor [START_REF] Sedov | On the problem of the economic system in Angkor Cambodia in the IXXII centuries. Narody Asii i Afriki[END_REF]. The inscriptions of Ta Prohm and Preah Khan, both state temples of Jayavarman VII (r. 1181/1183 -c.1220 CE), describe in detail the large number of villages tasked with providing rice, goods, and labor to these institutions [START_REF] Coedès | La stèle de Pr´ah Khan d'Angkor[END_REF][START_REF] Coedès | La stèle de Ta-Prohm[END_REF][START_REF] Maxwell | The stele inscription of Preah Khan, Angkor. Udaya[END_REF].

For example, at Ta Prohm, inscriptions indicate that there were 12,000 people associated with the functions of this single temple and 66,625 people from 3,140 villages that provided goods and labor [START_REF] Coedès | La stèle de Ta-Prohm[END_REF]. However, state temples also owned agricultural lands and temple workforces [START_REF] Sedov | On the problem of the economic system in Angkor Cambodia in the IXXII centuries. Narody Asii i Afriki[END_REF][START_REF] Sedov | Angkor: Society and state[END_REF].

The AMA was not just an agricultural zone but a "theocratic" landscape (sensu [START_REF] Coningham | The state of theocracy: defining an early medieval hinterland in Sri Lanka[END_REF], in which temple communities organized the agricultural land, labor, rice surplus, sociopolitical, and religious life of its members. Epigraphic data suggest that the rulers, state officials, and other elites were actively engaged in the temple economy, particularly in reassignments of land and labor (e.g., [START_REF] Lustig | Following the non-money trail: Reconciling some Angkorian Temple Accounts[END_REF][START_REF] Moffat | Using ground penetrating radar to understand the failure of the Koh Ker Reservoir, Northern Cambodia[END_REF][START_REF] Ricklefs | Land and the law in the epigraphy of tenth-century Cambodia[END_REF]. While private land ownership was common, the King appeared to have had final authority regarding land claims, which facilitated an elite patronage system [START_REF] Mabbett | Kingship in Angkor[END_REF]. Although not organized in a formal hierarchy, the AMA temples were connected to the CCC through these temple-related economic networks. Additionally, the AMA included state-sponsored infrastructure in the form of transportation networks [START_REF] Hendrickson | Historic routes to Angkor: Development of the Khmer Road System (Ninth to Thirteenth Centuries AD) in Mainland Southeast Asia[END_REF], water management features, and embankments (below) (Fletcher et al., 2008a;Fletcher et al, 2008b Klassen andEvans, 2020), which tied this space into the CCC.

The CCC was the location of most of Angkor's massive, states-sponsored stone temples and contained the city's highest population densities at different points in its sequence, although densities fluctuated through time. Like the AMA landscape, the CCC also had extensive hydraulic features. Limited excavations within CCC temple enclosures suggest the presence of garden spaces around residential areas [START_REF] Castillo | The Khmer did not live by rice alone: Archaeobotanical investigations at Angkor Wat and Ta Prohm[END_REF]. In the CCC, temples are constructed of stone or brick and surrounded by occupation mounds (Fig. 3). Temple enclosures themselves may have served as urban neighborhoods and likely included the temple staff's habitation areas [START_REF] Carter | Urbanism and Residential Patterning in Angkor[END_REF][START_REF] Stark | Residential patterning at Angkor Wat[END_REF].

The CCC grew over time as various kings built new temples and transformed the landscape. Our model identifies 17 diachronic zones of temples and their associated occupation mounds (Fig. 2). The areas of some of these zones are estimated, as later temples and occupation mounds expanded over earlier ones. For example, our portions of the Pre Rup zone (or district, see [START_REF] Heng | Form, structure, and long-term Angkorian urbanism: A view from the Kok Phnov Site (9-15th centuries CE)[END_REF] were taken over later by the construction of Ta Prohm and Preah Khan temples. Similarly, the initial Royal Palace zone was subsumed by the later walled city of Angkor Thom (Fig. 2). In such cases, we drew from studies on the chronology of the urban core to delimit the extent of the CCC zones at different points in time (see Table S1 in Klassen et al., 2021 for a detailed discussion).

Methods

Angkor's landscape is a palimpsest, in the sense that the patterns we see on the surface today are the end product of multiple periods of human occupation and transformation spanning millennia, with newer developments often at least partially erasing the traces of previous urban and agricultural networks. Since the 19th century, one of the key challenges at Angkor has been to make sense of the complex, overlapping patterns that we see on the landscape, particularly when we look at it from above, and to organize the traces into some kind of chronological sequence. Although a limited number of archaeological excavations have provided radiocarbon dates and many of the major temple sites in the CCC include inscriptions with consecration dates, the vast majority of features on Angkor's landscape remain undated by absolute dating techniques, and increasingly we have come to rely on establishing webs of relative chronological information that are anchored, in places, to absolute dates from inscriptions or excavations, or to periods derived from art historical or architectural studies. Earlier publications discuss in detail our methods for dating AMA features at Angkor [START_REF] Klassen | Semi-supervised machine learning approaches for predicting the chronology of archaeological sites: A case study of temples from medieval Angkor, Cambodia[END_REF] and estimating Angkor's population (Klassen et al, 2021). We summarize these approaches below.

Table 1 Major developments and rulers at Angkor with associated population estimates in the Civic Ceremonial Center (CCC) Angkor Metropolitan Area (AMA) and embankments (BANKs).

Dating and population estimates in the CCC

Temple spaces were our primary analytic unit. Temples in the CCC are often associated with art historical data and inscriptions that provide their date of construction or consecration [START_REF] Klassen | Semi-supervised machine learning approaches for predicting the chronology of archaeological sites: A case study of temples from medieval Angkor, Cambodia[END_REF](Klassen et al., , 2021;;[START_REF] Lustig | Power and Pragmatism in the Political Economy of Angkor[END_REF][START_REF] Polkinghorne | Makers and Models: Decorative Lintels of Khmer Temples, 7 th to 11 th Centuries[END_REF].2 However, dating the CCC is not always as straightforward, as parts of this landscape were used and reused over time, obscuring previous habitation and use. Some scholars have suggested that the builders of Angkor's temples followed particular ritual practices in which temples were to be constructed on "pure soil," which required that meters of existing soil be removed and replaced by beds of sand (Dumarçay et al., 2001: 34). In many cases, this soil replacement obscures any previous habitation in the area, although excavations at Angkor Wat and Ta Prohm suggest some light prior habitation/use of these landscapes [START_REF] Carter | Urbanism and Residential Patterning in Angkor[END_REF][START_REF] Carter | Temple occupation and the tempo of collapse at Angkor Wat, Cambodia[END_REF][START_REF] Sonnemann | The buried 'Towers' of Angkor Wat[END_REF]. At Angkor Thom, the orthogonally arranged city was developed in three phases beginning in the late 9th century CE, which continued until it was seemingly formalized with the construction of an enclosure wall by Jayavarman VII in the 12th century CE [START_REF] Gaucher | L'enceinte d'Angkor Thom: archéologie d'une forme et chronologie d'une ville[END_REF][START_REF] Gaucher | L'archéologie urbaine appliquée à un site archéologique: l'exemple d'Angkor Thom (Cambodge), capitale du royaume khmer angkorien[END_REF]. These transformations complicate our understanding of the landscape's evolution; however, we attempt to incorporate all such factors into our model (see additional discussion in Klassen et al., 2021).

Archaeologists have used numerous methods for estimating population size and density in urban areas [START_REF] Chamberlain | Demography in Archaeology[END_REF][START_REF] Hassan | Demographic archaeology[END_REF]. Early studies estimated population by counting residential structures and estimating the number of people per structure [START_REF] Nelson | Shellmounds of the San Francisco Bay region[END_REF] or making similar calculations by considering floor area [START_REF] Narroll | Floor area and settlement population[END_REF][START_REF] Wiessner | A functional estimator of population from floor area[END_REF]. Ethnographic data about household size has been valuable for estimating the number of people per household [START_REF] David | The Fulani Compound and the Archaeologist[END_REF][START_REF] Kolb | Demographic estimates in archaeology: Contributions from ethnoarchaeology on mesoamerican peasants[END_REF]. Communities with robust mortuary data have used skeletal remains to model populations (see [START_REF] Milner | Paleodemography: Problems, progress, and potential[END_REF] for a review of this method and its challenges). Other studies have taken a broader approach by considering available natural resources and the landscape's carrying capacity [START_REF] Zorn | Estimating the population size of ancient settlements: Methods, problems, solutions, and a case study[END_REF]. Scholars working in time periods with historical documents have used these resources to complement archaeological data (e.g., [START_REF] Jones | Using spatial analysis to estimate depopulation for Native American populations in northeastern North America, AD 1616-1645[END_REF][START_REF] Kowalewski | Scale and the explanation of demographic change: 3,500 years in the Valley of Oaxaca[END_REF]. More recent studies have used innovative methods to better estimate population, including the study of fecal stanols as a means of measuring population increases and decreases on a landscape [START_REF] White | Fecal stanols show simultaneous flooding and seasonal precipitation change correlate with Cahokia's population decline[END_REF], lidar data [START_REF] Inomata | Archaeological application of airborne LiDAR to examine social changes in the Ceibal region of the Maya lowlands[END_REF], and agent-based modeling [START_REF] Kohler | Modelling prehispanic Pueblo societies in their ecosystems[END_REF] to identify residential structures more accurately.

These methods are difficult to apply at Angkor. Only a handful of skeletal remains have been uncovered as the dead were largely cremated in the Angkor period [START_REF] Pottier | ´A La Découverte D'un Hˆopital Angkorien: Résultats Préliminaires D'une Campagne Archéologique Au Prasat Tromoung[END_REF].

Identifying dwelling spaces has been challenging due to the ephemeral nature of Angkorian habitation structures [START_REF] Carter | The Angkorian House[END_REF]; see also [START_REF] Graham | Maya cities and the character of a tropical urbanism[END_REF]. Early scholars were aware of occupation mounds around Angkor and attempted to map them, but were hampered by the dense forest [START_REF] Stark | Residential patterning at Angkor Wat[END_REF]. Despite this, numerous estimates for Angkor's population have been proposed, evolving as conceptions of Angkor's urban form have shifted over time (see Table 2).

Several of these methods have looked at the carrying capacity of the landscape and the population that could be supported based on the hydraulic network's development. The most recent and comprehensive estimate by [START_REF] Lustig | Water and the Transformation of Power at Angkor, 10th to 13 th Centuries A[END_REF] argues for a total population of 750,000 people at Angkor's height, based on a 1500 km2 area and assuming both of the largest water storage tanks (the East and West Baray) were in use but were not irrigating rice fields to the south. Despite usage in the comparative literature (e.g., [START_REF] Chase | Urbanism and anthropogenic landscapes[END_REF]Diamond, 2011: 539;[START_REF] Fletcher | Tropical environments and trajectories to low-density settlement forms[END_REF][START_REF] Stone | Divining Angkor[END_REF], this number was never meant to be definitive. Instead, it was an estimate of rice productivity and the carrying capacity of the Angkor region [START_REF] Lustig | Water and the Transformation of Power at Angkor, 10th to 13 th Centuries A[END_REF]. More recently, several scholars have provided population estimates for some of the enclosure areas within the CCC based on archaeological excavations and recently acquired lidar data (Table 2).

With lidar data, the mounded residential areas across the Greater Angkor Region have become more visible, even where they are covered by dense vegetation, allowing for more precise identification of residential spaces [START_REF] Evans | Uncovering archaeological landscapes at Angkor using lidar[END_REF]. Nevertheless, we are still unable to see individual house structures. To remedy this, we drew on recent archaeological work at Angkor Wat (Klassen et al., 2021;[START_REF] Stark | Residential patterning at Angkor Wat[END_REF]. A horizontal excavation on a single mound in the Angkor Wat enclosure in 2015, as well as numerous smaller excavations on discrete occupation mounds, indicated only one household per mound, with each mound measuring approximately 600 m2 in size. Although Cambodian households can include nuclear and extended families with varying numbers of children, ethnographic data suggests a preference for nuclear families with ethnographic surveys noting approximately five people per household (Delvert, 1961: 319;Ebihara, 2018: 51-68, 266;Ebihara, 1977: 52;[START_REF] Heuveline | Households and family processes[END_REF]Kalab, 1968: 525). Worldwide ethnographic studies also suggest that approximately five people are typical for most households (Hassan, 1978: 58).

To estimate the CCC population, we used a method we call the "mound method" in which the total square meters of mounded occupation features, including occupation mounds, pond embankments, and linear embankments were calculated. We then assumed that each household of five required approximately 600 m2 (see also discussion in Klassen et al., 2021). For example, at Angkor Wat, we extrapolated the mound-depression pattern seen in the eastern portion of the Angkor Wat enclosure across the entire enclosure to estimate a total of 271-278 mounds and a population of 1355-1390 persons.

We view this 600 m2 per household measurement as merely a beginning point based on the best currently available evidence for estimating the number of potential households, and by extension the total population at Angkor. A recent ethnoarchaeological study of household space around the ancient site of Bagan, Myanmar estimated the average household compound area to be 760 m2, close to our estimate at Angkor (Talving-Loza, 2020). We acknowledge that there was likely variation in household space in the past. Historical data has suggested that Angkorian households varied by size and status (Zhou, 2007: 49-50), and ethnographic studies also suggest that household size and density varied in village settings (Delvert, 1961: 180-198, 204;Ebihara, 2018: 41;[START_REF] Kalab | Study of a Cambodian Village[END_REF][START_REF] Prak | Wooden houses of the early twentieth century: Settlement patterns, social distinction and ethnicity[END_REF]. Rural households may have encompassed more space for gardens or tending animals than those in the CCC [START_REF] Bâty | Le tertre E à Trapeang Ropou Approche archéologique et géomorphologique d'un habitat angkorien[END_REF]. We also expect that further excavations will refine our estimate for household size in different contexts. At Ta Prohm, for example, not all mounds within the enclosure seem to have been as intensively inhabited [START_REF] Carter | Urbanism and Residential Patterning in Angkor[END_REF].

Table 2. Summary of previous population and density estimates proposed for Angkor.

It is worth noting that the 13th century Chinese visitor to Angkor, Zhou Daguan, described slaves associated with households in Angkor, observing that "most families have a hundred or more of them; a few have ten or twenty; only the poorest have none at all" (Zhou 2007: 58-59). These slaves are described as ethnic minorities who had little status within Angkor's society [START_REF] Mabbett | Some remarks on the present state of knowledge about Slavery in Angkor[END_REF] and only allowed to "sit or sleep under the house" (Zhou, 2007: 59). It is unclear how to interpret this evidence when calculating household size at Angkor. Excavations within the CCC have not uncovered evidence for people such as slaves living underneath houses [START_REF] Carter | Urbanism and Residential Patterning in Angkor[END_REF][START_REF] Heng | Form, structure, and long-term Angkorian urbanism: A view from the Kok Phnov Site (9-15th centuries CE)[END_REF][START_REF] Stark | Residential patterning at Angkor Wat[END_REF]. It is unlikely that even ten slaves could easily live underneath an average-sized house and would therefore require additional living quarters. Zhou (2007: 59) also implies that some of these slaves may have lived outside the city. In both cases then, we believe we have accounted for this population in our model. Overall it is likely that a large portion of Angkor's population was not free and would fall under some category of slave [START_REF] Lustig | New Insights into "les Interminables Listes Nominative d'Esclaves" from Numerical Analyses of the Personnel in Angkorian Inscriptions[END_REF][START_REF] Mabbett | Some remarks on the present state of knowledge about Slavery in Angkor[END_REF].

Dating and population estimates in the AMA

Most temples in the AMA do not have accessible datable material culture or inscriptions and the "mound method" is difficult to apply in this zone; therefore, we used different methods to calculate dates and population estimates. In the AMA, over 1,100 prasat-trapeang (temple-pond) configurations have been identified and mapped [START_REF] Klassen | Top-down and bottom-up water management: A diachronic model of changing water management strategies at Angkor, Cambodia[END_REF]Klassen et al.2018). The AMA temple dates were estimated using an algorithm that used a combination of multiple linear regression and graph-based semi-supervised machine learning to predict temple dates with a 49-66year average absolute error (see full discussion in [START_REF] Klassen | Semi-supervised machine learning approaches for predicting the chronology of archaeological sites: A case study of temples from medieval Angkor, Cambodia[END_REF].

As noted earlier, these temples are thought to be the center of Angkorian-period communities.

Occupation mounds within the AMA are not as visible in the CCC, and Angkorian inscriptions are of limited utility. While many describe the numbers of temple personnel and even the names of villages and lands donated (Lustig andLustig 2013, 2019;[START_REF] Lustig | Following the non-money trail: Reconciling some Angkorian Temple Accounts[END_REF], they are non-specific regarding the size and the demographic make-up of villages. However, some temple communities do have surviving occupation mounds. With these temple communities, we applied an algorithm originally devised by [START_REF] Hanson | A systematic method for estimating the populations of Greek and Roman settlements[END_REF] to provide spatial resolution to our population estimates. This algorithm assumes that density increases with the size of the occupation mounds. Ethnographic data suggests that approximately 100 families of five people were associated with each temple community [START_REF] Delvert | Le paysan cambodgien[END_REF] see also [START_REF] Kalab | Study of a Cambodian Village[END_REF]). Based on this understanding, we adjusted the Hanson and Ortman algorithm, so the outputs have a mean population of 497. For temples without surviving occupation mounds, we assigned a population of 497 people (see further discussion in Klassen et al., 2021).

As in the CCC, the AMA landscape was dynamic. Over time, land belonging to lower-status families or corporate groups appears to have been sold to higher-ranking elites [START_REF] Lustig | Losing ground: Decline of Angkor's middle-level officials[END_REF]. Archaeological evidence suggests that smaller temples may have been replaced by or superseded by larger temples. For example, excavations at the site of Trapeang Thlok show the site was in use only from the end of the 10th century to the mid-11th century CE when it was seemingly abandoned, with the population possibly shifting to the larger nearby temple sites of Prasat Trapeang Ropou or Prasat Prei [START_REF] Bâty | Les fouilles de l'áeroport de Siem Reap à Angkor[END_REF]. Determining the longevity of occupation at many sites will require similar careful archaeological excavation. However, in our model, we argue that populations of smaller temple communities would have been aggregated into those of large temples after the land was acquired. Therefore, once founded, the associated temple populations remain on the landscape, even if their affiliations, labor, and agricultural products were moved to a larger temple (see further discussion in Klassen et al., 2021).

Dating and population on the BANKs

The final form of occupation was on embankments (BANKs) of large water management features and roads. Evidence for occupation on the BANKs includes scatters of domestic debris such as ceramics on the surface and similar debris in the channels along with dark organic deposits (Fletcher et al., 2003: 109-111). These spaces may have been occupied by recent migrants to the city, as they offered land for housing that was not controlled by existing AMA communities, but this hypothesis requires further testing (Fletcher et al., 2003: 110-112;Klassen et al. 2021).

Angkor's hydraulic network has been reconstructed with a reasonable degree of confidence [START_REF] Fletcher | Angkor: a provisional map history of Greater Angkor from ancestry to transformation[END_REF]Fletcher et al., 2008b). While some hydraulic network elements (e.g., the massive East Baray) can be dated from inscriptions, other BANKs were indirectly dated by their spatial and functional relationship with well-dated temples or based on the superpositioning of features on a landscape. Features with unknown dates used a relative system of grouping features with other features that either date to the same time period or date to an earlier time period (see further discussion of these methods in Klassen et al., 2021).

The BANKs population was calculated assuming that the widest surviving part of the embankment represented the width of the embankment at the time of construction. We used our "mound method" described above to estimate household size on the embankments and with the same household composition. Preliminary surveys suggest that population density on the BANKs decreased farther from Angkor's CCC (Roland Fletcher, personal communication). Until further research can be done to determine variable population density along the BANKs, we report the maximum population on these features and note that the actual population likely fell within a range between zero and the population maximum (see Klassen et al., 2021).

To be sure, these population estimates are models that require further testing. Additional data from residential areas in both the CCC and AMA are needed to determine if the average household size, calculated here based on mounds within Angkor Wat, was typical or if this varied over time and space. Similarly, ethnographic data demonstrates that household composition was diverse and frequently changed over time (e.g., [START_REF] Ebihara | Residence patterns in a Khmer Peasant Village[END_REF]. As many house mounds in the AMA are missing, it is also difficult to determine exactly how many households were affiliated with a particular temple and ethnographic data suggest some flexibility in how households could support various pagodas (e.g., [START_REF] Kalab | Study of a Cambodian Village[END_REF]). Excavations to identify datable material, would also help refine the timing of sites whose dates were estimated based on machine learning algorithms. Additionally, habitation on embankments has not been thoroughly examined and so our population estimates for these locations are the most speculative. We are curious if habitation was as intense on these features and if material culture might tell us more about who was living on these mounds and their occupations.

Our reliance on ethnographic data to estimate household and community sizes is both a boon and a limitation. The exact composition of an Angkorian household may be difficult to determine, especially given a lack of skeletal remains that might facilitate understandings of biological family relationships or clear outlines of dwelling size and rooms within a dwelling space. Non-kin members of households, such as slaves or servants, are also difficult to account for. Nevertheless, we feel that the ethnographic data, provides the most informed option for estimating population given that other source of data for estimating household size are absent.

Discussion

Table 1 lists the total number of people in the CCC, AMA, and BANKs during each period (see also Fig. 4). We note that at its height in the 12-13th centuries CE, Angkor's population could have been as high as 900,000 people if the BANKs were fully inhabited. We also observe different rates of growth in these three occupation zones, with major population growth in the AMA in Period 2. However, in subsequent periods, we observe slower growth in the AMA with increasing population density in the CCC (Fig. 5 and Tables 3 and4). This culminates in the highest population density in the CCC associated with Period 5 and the reign of Jayavaraman VII, who intensified and formalized Angkorian space. These developments were short-lived, however, as Angkor began its slow decline in the 13th and 14th centuries CE. In the sections below, we discuss each period in detail and the historical developments that were shaping Angkor's agro-urban landscape.

Period 1-770-888 CE: Pre-Angkor period and the early cities of Mahendraparvata and Hariharālaya

We begin our Period 1 in 770 CE with the habitation of two early Angkorian capital cities (Mahendraparvata and Hariharālaya) and a third likely population center near what would become the West Baray (Bhavapura) (Fig. 2). 3 We estimate the total population of Angkor in this period to be approximately 250,000 people (Fig. 4 and Table 1). The two capitals of Hariharālaya and Mahendraparvata have the highest population densities of approximately 16 persons per hectare (henceforth p/ ha) and monumental construction and infrastructure development we consider to be typical of CCC zones. The third population center, Bhavapura (discussed below), has a slightly lower population density of approximately 13p/ha (Table 4). The presence of temple communities in the AMA is sparse; just over 200 km2 of Angkor's AMA contains less than 5p/ha (Table 3) with approximately 70,000 people. However, if the embankments were fully inhabited at this time, this would add about 89,000 people to the AMA landscape.

Mahendraparvata, located on Phnom Kulen (Fig. 1), contains the massive Rong Chen pyramid temple, where Jayavarman II was supposedly declared a universal monarch establishing the start of the Angkor kingdom [START_REF] Coedès | The Indianized States of Southeast Asia[END_REF][START_REF] Coedès | Pour mieux comprendre Angkor[END_REF][START_REF] Coedès | Les Stèles de Sdok Kak Thom, Phnom Dandak, et Prah Vihar[END_REF]. Recent studies have demonstrated that this was a large, planned city of approximately 40-50 km2, organized on a grid with occupation areas, temples, linear causeways, hydraulic features including a large reservoir [START_REF] Chevance | Mahendraparvata: an early Angkor-period capital defined through airborne laser scanning at Phnom Kulen[END_REF]. The construction of these hydraulic features would have likely required a large labor force during the early phases of urban development on the mountain [START_REF] Chevance | Mahendraparvata: an early Angkor-period capital defined through airborne laser scanning at Phnom Kulen[END_REF][START_REF] Penny | The environmental impact of Cambodia's Ancient City of Mahendraparvata (Phnom Kulen)[END_REF]. The city appears to date to the late 8th-early 9th centuries CE, although the presence of at least two Pre-Angkorian temples points towards this location's importance during the Pre-Angkor period [START_REF] Chevance | Mahendraparvata: an early Angkor-period capital defined through airborne laser scanning at Phnom Kulen[END_REF]. Calculating population at Mahendraparvata is challenging as there are not clear occupation mounds as seen in the lowland floodplains. For this reason, we estimated the population density to be similar to that at Hariharālaya (see Klassen et al., 2021).

Table 3. Amount of km2 with densities less than 5, 5-10, and greater than 10 people/ha.

The expansion of Hariharālaya as a capital is also associated with Jayavarman II, in the early 9th century CE, although many of the major constructions at Hariharālaya, including aspects of the brick towers of Preah Kô, the Indratatāka reservoir, and the Bakong temple are affiliated with the ruler Indravarman I (877-889 CE). Archaeological and epigraphic data suggest long-term habitation in the Hariharālaya area prior to the Angkor period. A recently identified inscription from the Bakong temple might be one of the oldest in the region, dating to the 6-7th centuries CE [START_REF] Pottier | De l'ancienneté de Hariharālaya. Une inscription préangkorienne opportune à Bakong[END_REF]. Excavations around the site of Trapeang Phong also indicate habitation from the 7th century CE [START_REF] Pottier | Nouvelles données sur les premières cités angkoriennes[END_REF]Pottier and Bolle, 2009). Recent archaeological and palynological data suggest the construction of the Bakong began in the late 8th century CE, prior to Indravarman I's reign [START_REF] Penny | Vegetation and land-use at Angkor, Cambodia: a dated pollen sequence from the Bakong temple moat[END_REF][START_REF] Pottier | Beyond the temples: Angkor and its territory[END_REF]. By the 9th century CE, the population at Hariharālaya expanded, especially around the royal palace, Prei Monti [START_REF] Pottier | Beyond the temples: Angkor and its territory[END_REF]Pottier et al., 2008;Pottier et al., 2009;[START_REF] Pottier | Mission Archéologique Franco-Khmère sur l'Aménagement du Territoire Angkorien (MAFKATA): Campagne 2007 Rapport[END_REF]. Using the mound method, we estimate the population of this city to be approximately 39,000 people.

The area around the future site of the West Baray and the Ak Yum, believed to have been known as Bhavapura, presents a unique challenge [START_REF] Pottier | Nouvelles données sur les premières cités angkoriennes[END_REF]. This region has a long history of habitation.

Burials dating from the Bronze Age (approx. 1000 BCE) were identified in the West Baray (Pottier, 2006b;[START_REF] Pottier | Koh Ta Meas, un site préhistorique dans le Baray Occidental Rapport Préliminaire[END_REF], and Iron Age or Protohistoric burials from the early-mid first millennium CE were uncovered during excavations at the nearby temple site of Prei Khmeng [START_REF] O'reilly | Revisiting Prei Khmeng: The excavation of an iron age settlement and cemetery in Cambodia[END_REF][START_REF] Pottier | Prei Khmeng: Synthese et phasage du tertre[END_REF]. Several inscriptions and large temples were located in this region, including Prei Khmeng, Ak Yum, and Wat Khnat, testifying to the significant population in this area in the 7th and 8th centuries CE (Pottier, 2006a;[START_REF] Pottier | Nouvelles données sur les premières cités angkoriennes[END_REF]Pottier et al., 2001a;Pottier et al., 2001b). The Bhavapura settlement contained powerful rulers and may have included a "proto-baray" and associated rice fields (Fletcher et al., 2017: 277;Hawken, 2013: 360;Klassen and Evans, 2020: 5;[START_REF] Pottier | Nouvelles données sur les premières cités angkoriennes[END_REF][START_REF] Soutif | Organisation religieuse et profane du temple khmer du VIIème au XIIIème siècle, Linguistique[END_REF].

Unfortunately, much of the habitation in this area was destroyed by the construction of the West Baray in the 11th century CE. In our model, we gave this area the same density as Pre Rup, whose mounds are visible and have been mapped. The surviving remains in this zone suggest a lower density than Hariharālaya. [START_REF] Fletcher | Angkor: a provisional map history of Greater Angkor from ancestry to transformation[END_REF] suggest that Bhavapura may have been approximately 35 km2. We estimate the total population at approximately 26,000 people; however, these estimates will need to be refined with further archaeological investigation.

Period 2-889-1001 CE: Initial foundation of Yaśodharapura, Jayavarman IV's capital at Koh Ker (Chok Gargyar), and return to Yaśodharapura

In 889 CE, the ruler Yaśovarman I came to power and established a new capital, Yaśodharapura, centered around the natural hill of Phnom Bakheng where he also built a temple [START_REF] Gaucher | Angkor, histoire urbaine et archéologie[END_REF]Pottier, 2000a) (Fig. 1). Inscriptions (K. 464 and K. 558) date the consecration of gods at Phnom Bakheng temple to 907 CE [START_REF] Jacques | History of the Phnom Bakheng Monument[END_REF][START_REF] Jacques | IV. Études d'épigraphie cambodgienne[END_REF]. During this period, we observe two major population centers within the CCC (Fig. 2). The first is around the temple of Phnom Bakheng extending to the north to the area around the Royal Palace and Phimeanakas and to the east around the Krâvan temple (Fig. 2 zones 15-17). Although heavily disturbed by later modifications and more intensive habitation during the reign of Jayavarman VII, excavations within Angkor Thom suggest habitation in this area dating at least to the 9th century CE and the period of Yaśovarman I [START_REF] Gaucher | L'enceinte d'Angkor Thom: archéologie d'une forme et chronologie d'une ville[END_REF][START_REF] Gaucher | L'archéologie urbaine appliquée à un site archéologique: l'exemple d'Angkor Thom (Cambodge), capitale du royaume khmer angkorien[END_REF]. Inscriptions K. 291 and K. 576 also imply that Yaśodharapura reached this palace area (Coedès, 1937: 199;Finot, 1925: 307) and ceramics dating to the 9th century CE have been identified in excavations within Angkor Thom [START_REF] Gaucher | L'archéologie urbaine appliquée à un site archéologique: l'exemple d'Angkor Thom (Cambodge), capitale du royaume khmer angkorien[END_REF][START_REF] Polkinghorne | Casting for the King: The Royal Palace bronze workshop of Angkor Thom[END_REF]. The population of these three zones totals nearly 30,000 people. A second population center was around the temple of Pre Rup and the area of the Eastern Baray, also called the Eastern District (Heng et al., under review) (Fig. 2, zone 13). The mounds in the Eastern District are less disturbed; therefore, we are able to use the "mound method" to estimate population within this region and assume that similar densities were in place in the Yaśodharapura area with a population of almost 14,000 people.

It is unclear why Yaśovarman I decided to shift the location of the capital from Hariharālaya. As noted above, there had been a population living in this area during Period 1 and likely earlier (Groslier, 1979: 165-166). Groslier notes that Yaśovarman had a "predilection" for hilltop temple sites (Groslier, 1979: 172). Hydrological studies also demonstrate that this area had a higher and less variable water table than Hariharālaya, which may have facilitated rice agriculture with groundwater access during the dry season [START_REF] Acker | Mysteries of Angkor revealed: Hydrology and the siting of Angkor[END_REF]. Increased water management certainly seems to have been an important focus during this period. Inscriptions (K. 280-283) describe the East Baray's construction in association with King Yásovarman I in the late 9th century CE (Bergaigne, 1893: 407-408;Coedès, 1932: 108-109). During this period, the creation of the channel known as the Siem Reap River brought water closer to the newly established capital [START_REF] Acker | Mysteries of Angkor revealed: Hydrology and the siting of Angkor[END_REF][START_REF] Groslier | VII. La cité hydraulique angkorienne: exploitation ou surexploitation du sol?[END_REF][START_REF] Lustig | Did traditional cultures live in harmony with nature? Lessons from Angkor, Cambodia[END_REF]. The aim of the increased investment in water management is believed to have been to facilitate agricultural production [START_REF] Fletcher | The dynamics of Angkor and its landscape[END_REF]Fletcher et al. 2008a;Fletcher et al. 2008b;[START_REF] Groslier | VII. La cité hydraulique angkorienne: exploitation ou surexploitation du sol?[END_REF]. The labor of a large number of people would have been required for the construction of the East Baray and related channel features. Pottier (2000b: 105) has estimated that a workforce of 148,000 people could have taken three months to construct the larger West Baray. It is likely that such a workforce would have been drawn from these surrounding AMA populations.

Table 4. Population estimates and densities of sites mentioned in the text.

Despite the infrastructure development at Yaśodharapura during Period 2, our model estimates a population decrease to approximately 77,000 people in the CCC during this period. Part of this may be due to the estimates used in our model that was based on the visible occupation mounds at Pre Rup, which are lower density than those at Hariharālaya. However, there were additional changes taking place in Angkor's landscape. During this period, King Jayavarman IV (r. 928-941 CE) ruled from an alternative capital site at Koh Ker (called Chok Gargyar) approximately 80 km northeast of Angkor in what is now Preah Vihear province (Fig. 1). Although well-located for access to stone, recent work has identified serious problems with the city's water management system that likely affected its viability as a long-term capital (Evans, 2010;[START_REF] Lustig | Evidence for the breakdown of an Angkorian hydraulic system, and its historical implications for understanding the Khmer Empire[END_REF][START_REF] Moffat | Using ground penetrating radar to understand the failure of the Koh Ker Reservoir, Northern Cambodia[END_REF]. The establishment of this alternative capital may have drawn some population away from the CCC at Yaśodharapura [START_REF] Hall | Re-evaluating the occupation history of Koh Ker, Cambodia, during the Angkor period: A palaeo-ecological approach[END_REF]. However, this period also saw the foundations of numerous temples in the AMA by non-royal officials (discussed below and Lustig and Lustig, 2019).

In the mid-10th century CE, King Rājendravarman II (r. 944-968 CE) returned the capital to Yaśodharapura from Koh Ker, where it remained the location of Angkor's capital for several centuries, growing and expanding with subsequent kings. Rājendravarman II constructed the large state temple of Pre Rup near the East Baray, inaugurating it in 961 CE [START_REF] Coedès | L'Inscription de Baksei Camkron[END_REF]. Additional modifications were made to the East Baray during this period, including the construction of the East Mebon temple on a man-made island in the middle of the baray (Dumarçay et al., 2001: 64-65;Fletcher et al., 2008b;[START_REF] Groslier | VII. La cité hydraulique angkorienne: exploitation ou surexploitation du sol?[END_REF].

Archaeological evidence suggests continued habitation at Bhavapura until the construction of the West Baray in the 11th century CE (Pottier et al., 2001a;Pottier et al., 2001b). For these reasons, we have left these population estimates unchanged until that time. Archaeological and palynological data suggest some depopulation at Hariharālaya with the establishment of Yaśodharapura [START_REF] Penny | The Holocene history and development of the Tonle Sap, Cambodia[END_REF]. However, archaeological excavations at Trapeang Phong show evidence for continued habitation in this area until the 15th century CE, and the central tower of Bakong was renovated in first half of the 12th century CE (Boisselier, 1952: 223;Pottier and Bolle, 2009). Our model leaves a population of approximately 37,000 people, moving only a small elite population of approximately 2,000 people to Yásodharapura. In contrast, Mahendraparvata appears to have been depopulated during this period, although later features indicate the area was not completely abandoned [START_REF] Chevance | Mahendraparvata: an early Angkor-period capital defined through airborne laser scanning at Phnom Kulen[END_REF]. For this reason, we have reduced the population at Mahendraparvata to 1000 people. This number is merely an estimate and will need to be refined with further archaeological investigation.

While the CCC population was seemingly shrinking, Angkor's AMA population saw a dramatic jump, from 70,000 to approximately 318,000 people. The total area of land with a density of <5 people per hectare expands from 201 km2 to 687.5 km2 (Tables 1 and3). Inscriptional evidence suggests that non-royal officials established many new temple communities in the AMA during this period [START_REF] Klassen | Semi-supervised machine learning approaches for predicting the chronology of archaeological sites: A case study of temples from medieval Angkor, Cambodia[END_REF][START_REF] Lustig | Losing ground: Decline of Angkor's middle-level officials[END_REF]. Additionally, the water management system and road and transportation networks expanded, especially in the northeastern portion of Angkor's territory [START_REF] Hendrickson | Historic routes to Angkor: Development of the Khmer Road System (Ninth to Thirteenth Centuries AD) in Mainland Southeast Asia[END_REF]. Many of these new temple communities in the 10th and 11th centuries CE (our Periods 2 and 3) specifically tend to cluster around the state-sponsored hydraulic infrastructure, including the construction of baray [START_REF] Klassen | Top-down and bottom-up water management: A diachronic model of changing water management strategies at Angkor, Cambodia[END_REF]. Combined with inscriptional evidence, Klassen and Evans (2020: 6) hypothesize that these newly established temple communities practiced a form of bottom-up organization where they had some degree of local autonomy over their associated land. These combined factors seem to have allowed for the expansion of Angkor's AMA into a massive agro-urban center [START_REF] Klassen | Top-down and bottom-up water management: A diachronic model of changing water management strategies at Angkor, Cambodia[END_REF].

Period 3-1002-1112 CE: Reign of Sūryavarman I

In the early 11th century CE, there was an internal struggle for power between two rival kings, with Sūryavarman I (1002/1003-1050 CE) ultimately claiming the throne, which begins our Period 3 [START_REF] Vickery | The Reign of Sūryavarman I and Royal Factionalism at Angkor[END_REF]. Sūryavarman I continued habitation within Yásodharapura and modified some of the Royal Palace area and the temple of Phimeanakas, while also constructing numerous temples outside of the capital [START_REF] Jacques | The Khmer Empire: Cities and Sanctuaries from the 5th to the 13th Century[END_REF]. As part of these expansions, Sūryavarman I also seems to have formalized some of Angkor's road networks [START_REF] Hendrickson | Historic routes to Angkor: Development of the Khmer Road System (Ninth to Thirteenth Centuries AD) in Mainland Southeast Asia[END_REF].

During this period, the dramatic increase in the AMA population begins to slow, with only about 112,000 new people during this more than 100 year period. In contrast, the CCC expands to approximately 117,000 people. The CCC's growth is likely due to the formalization of the Royal Palace compound, including the nearby temples of the Baphuon [START_REF] Leroy | First direct dating for the construction and modification of the Baphuon Temple Mountain in Angkor, Cambodia[END_REF] and Phimeanakas in the area that would later become incorporated into Angkor Thom [START_REF] Gaucher | L'enceinte d'Angkor Thom: archéologie d'une forme et chronologie d'une ville[END_REF]. King Sūryavarman I is also associated with the construction of the West Baray in the western part of the capital (Pottier, 2000b). The construction of this feature would have required a large labor force, likely drawn from AMA populations and disrupted much of the earlier settlement of Bhavapura.

While one might expect continued expansion of AMA populations due to the West Baray's construction, our model predicts only modest growth. [START_REF] Klassen | Semi-supervised machine learning approaches for predicting the chronology of archaeological sites: A case study of temples from medieval Angkor, Cambodia[END_REF] have noted a decline in new AMA temple constructions from the 11th century CE onward. Inscriptions also indicate a shift in the titles of individuals buying and selling land during the 10th century CE, prior to Sūryavarman I's reign. Inscriptions demonstrate changing land ownership, where high-ranking elites appeared to have monopolized landholding at the expense of the lower status individuals and communal/corporate groups [START_REF] Lustig | Losing ground: Decline of Angkor's middle-level officials[END_REF]cf. Vickery, 1985). Additionally, the number of tax immunities granted to new temple foundations appears to decline in the 11th century CE, which would have discouraged the formation of new temples [START_REF] Lustig | Losing ground: Decline of Angkor's middle-level officials[END_REF]. Taken together, it appears that during the 11th century CE, there was a shift from the establishment of new temples on undeveloped land to elite consolidation of land ownership [START_REF] Klassen | Top-down and bottom-up water management: A diachronic model of changing water management strategies at Angkor, Cambodia[END_REF][START_REF] Lustig | Losing ground: Decline of Angkor's middle-level officials[END_REF]. These top-down controls appear to have slowed Angkor's AMA population growth.

Period 4-1113-1180 CE: Reign of Sūryavarman II and construction of Angkor Wat

Our Period 4 begins with the next major king of Angkor, Sūryavarman II (1113-1149 CE), who came to power in the early 12th century CE and is responsible for Angkor's most famous temple, Angkor Wat. Like his namesake, he also expanded the Empire's borders. While we primarily associate this period with Sūryavarman II, a newly discovered inscription also describes a subsequent ruler, King Tribhuvanadityavarman, who took power after Sūryavarman II and ruled from 1149 to 1180 CE [START_REF] Sharrock | Cham-Khmer interactions in 1113-1220 CE[END_REF]. The inscription also recounts that he built "eight Buddhist sanctuaries" and was then killed during a Cham attack on Angkor in 1180 CE (Sharrock, 2018: 112). This new inscription suggests that Tribhuvanadityavarman was a more important ruler than previously supposed, and future research is needed to determine his impact on Angkor's history.

Our model predicts a continued slow population growth in both the CCC and AMA during this period. The CCC saw a population increase of only approximately 5,000 people. However, Angkor Wat's construction had major impacts on Angkor's socio-political landscape and may have inspired reorganization of habitation within the CCC. The construction of the temple itself would have required an immense number of laborers. Additionally, lidar images reveal a large series of square spirals south of Angkor Wat, whose function is not yet clear, but may have acted as large gardens [START_REF] Evans | Airborne laser scanning as a method for exploring long-term socioecological dynamics in Cambodia[END_REF].

During his reign, Sūryavaraman II invaded the neighboring kingdom of Champa in Vietnam and moved the Angkorian Empire farther into Thailand and the northern Malay Peninsula [START_REF] Coe | Angkor and the Khmer Civilization, Second Edition[END_REF][START_REF] Coedès | The Indianized States of Southeast Asia[END_REF]. One must wonder if this expansion and focus outside the Greater Angkor Region contributed to the slower growth of the AMA during this period (Table 1).

Period 5-1181/1183-1300 CE: Reign of Jayavarman VII

The ruler many consider to be Angkor's most celebrated king, Jayavarman VII, came to power at the end of the 12th century, which marks the beginning of Period 5. With Jayavarman VII's reign (1181/ 1183-c.1220 CE) came a period of dynamism. He was responsible for the greatest expansion of the Empire, massive building campaigns within the capital, and additions to the water management network [START_REF] Coedès | Pour mieux comprendre Angkor[END_REF]. Jayavarman VII is associated with the construction of five major temples in Angkor's CCC: the state temple of the Bayon, Banteay Kdei, Ta Prohm, Preah Khan, and Neak Pean on a small island within the Jayataṭāka baray [START_REF] Coedès | The Indianized States of Southeast Asia[END_REF][START_REF] Stern | Les monuments Khmers du style du Bayon et Jayavarman VII[END_REF]. Additionally, Jayavarman VII built large temples, such as Banteay Chhmar outside the Greater Angkor Region [START_REF] Sharrock | Banteay Chhmar: Garrison-temple of the Khmer Empire[END_REF], contributed to Angkor's expanding road networks [START_REF] Hendrickson | Historic routes to Angkor: Development of the Khmer Road System (Ninth to Thirteenth Centuries AD) in Mainland Southeast Asia[END_REF], and constructed small hospital chapels inside and outside the CCC [START_REF] Pottier | ´A La Découverte D'un Hˆopital Angkorien: Résultats Préliminaires D'une Campagne Archéologique Au Prasat Tromoung[END_REF][START_REF] Sharrock | The Grief of Kings Is the Suffering of Their Subjects": A Cambodian King's twelfth-century network of hospitals[END_REF].

We see another demographic increase during this period, with the population across Angkor reaching its peak-perhaps up to 900,000 people-and approximately 1000 km2 of the 3000 km2 study having been occupied (Tables 1 and3). This population growth is largely due to an increase in population in the CCC, from approximately 122,000 to 160,000 people, as the AMA and BANKs populations grew only slightly. In portions of the CCC, population density increased dramatically. For example, habitation around Preah Khan temple may have had a density as high as 75p/ha (Table 4). However, we note that excavations at the nearby Ta Prohm temple, also constructed by Jayavarman VII, suggest not all the mounds within the enclosure were equally or as intensively inhabited [START_REF] Carter | Urbanism and Residential Patterning in Angkor[END_REF] and based on these data have revised the population estimates down from that predicted by the mound-method.

Confirming that these enclosures were densely inhabited will require more fine-grained archaeological investigation.

Most scholars agree that late-12th -early-13th-century CE Angkor contrasted markedly with its preceding urban forms both in structure and worldview [START_REF] Coedès | Pour mieux comprendre Angkor[END_REF][START_REF] Coedès | The Indianized States of Southeast Asia[END_REF][START_REF] Gaucher | Angkor Thom, une utopie réalisée? Structuration de l'espace et modèle indien d'urbanisme dans le Cambodge ancien[END_REF][START_REF] Groslier | Inscriptions du Bayon[END_REF][START_REF] Hawixbrock | Jayavarman VII ou le renouveau d'Angkor entre tradition et modernite[END_REF][START_REF] Mus | Le sourire d'Angkor. Art, foi et politique bouddhiques sous Jayavarman VII[END_REF][START_REF] Sharrock | Garuda, Vajrapāni and religious change in Jayavarman VII's Angkor[END_REF], such changes likely explain its steep increase in population density. Jayavarman VII was a remarkably effective consolidator of previous state infrastructure: roads, bridges, and even some provincial capitals [START_REF] Hendrickson | Arteries of Empire: An operational study of transport and communication in Angkorian Southeast Asia (9th to 15th centuries CE)[END_REF][START_REF] Hendrickson | Historic routes to Angkor: Development of the Khmer Road System (Ninth to Thirteenth Centuries AD) in Mainland Southeast Asia[END_REF][START_REF] Hendrickson | Sparks and needles: Seeking catalysts of state expansions: a case study of technological interaction at Angkor, Cambodia (9th to 13th centuries CE)[END_REF]). Angkor's urban core also reflects this pattern in, for example, the formalization and walling of the Angkor Thom area [START_REF] Gaucher | L'enceinte d'Angkor Thom: archéologie d'une forme et chronologie d'une ville[END_REF]. Labor requirements to undertake such massive state projects would have placed demands on both AMA and core populations and likely brought more residents to the city center [START_REF] Klassen | Top-down and bottom-up water management: A diachronic model of changing water management strategies at Angkor, Cambodia[END_REF].

While there would have been an increased demand for agricultural production to support this large population of non-producers living in the CCC, recent work by Klassen et al. (2021) suggests that the heightened demand for surplus may not have led to the immiseration of farmers. Using settlement scaling theory, the authors argue that supra-household scale organization of agriculturalists facilitated through temple communities (whether owned on a local level or by elites) likely allowed for increasing returns to farming labor that did not necessitate decreased fallowing, more hours of work, or increased technological inputs. Further, the patterning of agricultural temple communities is consistent with the Alonso-Mulls-Mills model [START_REF] Alonso | Location and Land Use: Toward a General Theory of Land Rent[END_REF][START_REF] Brueckner | The structure of urban equilibria: A unified treatment of the Muth-Mills model[END_REF], where land is valued based on the commuting cost to the CCCs. This indicates that the urban development and form of medieval Angkor was beholden to the same processes that structure the urban form of contemporary cities (Klassen et al., 2021).

A population of 900,000 people would have exceeded the previously estimated landscape capacity of 750,000 people without irrigation from the baray [START_REF] Lustig | Water and the Transformation of Power at Angkor, 10th to 13 th Centuries A[END_REF]. Therefore one must wonder if Angkor's provincial zones were sending other food or staple finance to the capital (D' Altroy and Earle, 1985;[START_REF] Isendahl | Archaeology, history, and urban food security: integrating cross-cultural and long-term perspectives[END_REF]. For example, an inscription from one of Jayavarman VII's large state temples in the CCC, Ta Prohm, notes that 66,625 people from 3,140 villages supplied the temple with goods and labor [START_REF] Coedès | La stèle de Ta-Prohm[END_REF]. Our model predicts only 2000 people living within Ta Prohm's temple enclosure, with an additional 14,000 in the temple district; far below the numbers mentioned in the inscription. Therefore, there must have been additional villages outside the temple district, likely in the AMA and beyond, that would have provisioned Ta Prohm. Inscriptions note that small AMA temples would collect goods and products from their agricultural lands, a small portion of which were sent as tax to larger centralized temples [START_REF] Sedov | On the problem of the economic system in Angkor Cambodia in the IXXII centuries. Narody Asii i Afriki[END_REF]. However, no inscriptions suggest staple finance was sent from AMA or provincial temples to the capital [START_REF] Lustig | Water and the Transformation of Power at Angkor, 10th to 13 th Centuries A[END_REF][START_REF] Lustig | Power and Pragmatism in the Political Economy of Angkor[END_REF]. Instead, it appears that many temples would convert their staple finance to wealth finance or "high-value goods" that would be sent as tax to the capital [START_REF] Lustig | Losing ground: Decline of Angkor's middle-level officials[END_REF]. Several provincial zones, notably the province of Battambang were well-known in the 19th and 20th centuries CE for their fertile agricultural soils and rice productivity [START_REF] Nesbitt | Rice Production in Cambodia[END_REF]. It is plausible these regions were sending rice to the capital; however, no such material or epigraphic evidence yet exists for this practice.

Angkor's decline (after 1301 CE)

Following a population high in Period 5, Angkor's population began to fall. Accumulated archaeological evidence suggests that Angkor's decline started in the late 13th through 14th centuries CE, before the supposed sacking of Angkor by the Kingdom of Ayutthaya in 1431 CE [START_REF] Buckley | Climate as a contributing factor in the demise of Angkor, Cambodia[END_REF][START_REF] Carter | Temple occupation and the tempo of collapse at Angkor Wat, Cambodia[END_REF][START_REF] Fletcher | Fourteenth to sixteenth centuries AD. The case of Angkor and monsoon extremes in Mainland Southeast Asia[END_REF][START_REF] Hall | An integrated palaeoenvironmental record of Early Modern occupancy and land use within Angkor Thom[END_REF][START_REF] Penny | Geoarchaeological evidence from Angkor, Cambodia, reveals a gradual decline rather than a catastrophic 15th-century collapse[END_REF][START_REF] Penny | The demise of Angkor: Systemic vulnerability of urban infrastructure to climatic variations[END_REF]. The last Sanskrit inscription dates to 1327 CE, with the last major stone temple (Maṅgalārtha) constructed in 1295 CE (Briggs, 1951: 243, 251;Finot, 1925: 393-406). The growing influence of Theravāda Buddhism, which had emerged with a new fervour in the late 13th century CE, appears to have appropriated pre-existing power structures [START_REF] Thompson | Changing perspectives: Cambodia after Angkor[END_REF], though its relationship with the decline of Angkor as capital is unclear [START_REF] Polkinghorne | 17th and 18th century images of the Buddha from Ayutthaya and Lan Xang at Angkor Wat[END_REF].

Additionally, recent environmental studies have suggested that people were likely leaving the walled precinct of Angkor Thom in the early 14th century CE [START_REF] Hall | An integrated palaeoenvironmental record of Early Modern occupancy and land use within Angkor Thom[END_REF][START_REF] Penny | Geoarchaeological evidence from Angkor, Cambodia, reveals a gradual decline rather than a catastrophic 15th-century collapse[END_REF]. As noted above, some portion of this population may have been moving further south, as Early Modern capitals were located closer to present-day Phnom Penh, where China's trading potential was growing [START_REF] Polkinghorne | Reconfiguring kingdoms: The end of Angkor and the emergence of Early Modern period Cambodia[END_REF][START_REF] Vickery | Cambodia after Angkor, the Chronicular Evidence for the fourteenth to sixteenth centuries[END_REF][START_REF] Vickery | Cambodia and its neighbours in the 15th century[END_REF][START_REF] Polkinghorne | Early Modern Cambodia and Archaeology at Longvek[END_REF]. On top of this, a series of decades-long droughts and heavy monsoons severely impacted Angkor's water management network in the 14th and 15th centuries CE, which must have also impacted Angkor's agricultural productivity [START_REF] Buckley | Climate as a contributing factor in the demise of Angkor, Cambodia[END_REF]. If people were already leaving the CCC, one might wonder if the water network's maintenance was necessary as communities in the AMA could produce enough for themselves with their existing infrastructure (Fletcher et al., 2017: 283;Polkinghorne, 2018: 260). This is a question worthy of further investigation.

Accurately determining which portions of Angkor's landscape were still inhabited during this period is challenging. Recent archaeological studies have highlighted the dynamic and complex life histories of some of Angkor's temples and their populations. At Angkor Wat, there appears to be a break or decline in occupation mounds surrounding the temple, followed by a lighter re-occupation in the Early Modern period [START_REF] Carter | Temple occupation and the tempo of collapse at Angkor Wat, Cambodia[END_REF][START_REF] Stark | Residential patterning at Angkor Wat[END_REF]. Conversely, at Ta Prohm, archaeological evidence suggests no habitation or use of the temple following the 14th century CE [START_REF] Carter | Urbanism and Residential Patterning in Angkor[END_REF]. Some temples, such as the Baphuon, were heavily modified in the 15th century CE, indicating a significant population's presence to undertake these changes [START_REF] Leroy | First direct dating for the construction and modification of the Baphuon Temple Mountain in Angkor, Cambodia[END_REF]. Other archaeological and art historical studies have demonstrated continued habitation around Angkor [START_REF] Brotherson | Commerce, the Capital, & Community. Trade Ceramics, Settlement Patterns, & Continuity Throughout the Demise of Angkor[END_REF][START_REF] Castillo | Life goes on: Archaeobotanical investigations of diet and ritual at Angkor Thom, Cambodia (14th-15th centuries CE)[END_REF][START_REF] Polkinghorne | Evidence for the 15th century Ayutthayan occupation of Angkor[END_REF]. Recently, [START_REF] Fletcher | Fourteenth to sixteenth centuries AD. The case of Angkor and monsoon extremes in Mainland Southeast Asia[END_REF] have proposed a population of approximately 300,000 adults at Angkor by the early 14th century CE. We are currently unable to model population decline in Greater Angkor more accurately, as this will require careful archaeological excavation. Although there was a significant depopulation, this region was not abandoned or forgotten.

Conclusions

To summarize, several salient trends characterize the Angkor case study. The first involves initial nucleation in the urban core (Period 1) with three major population centers and a population density of 13-16p/ha. This was followed by a rapid AMA expansion in Period 2, which quadrupled the population in this zone. Angkor's total population during this period was approaching half a million people, depending on the density of habitation on the BANKs. Angkor's AMA always housed more people than its urban civic-ceremonial core. Such demographic imbalance coincided with the construction of new temple-based communities in the capital and the expansion of the city's water management network to include more of the metropolitan region. The AMA temple communities took advantage of this top-down state-sponsored infrastructure and relied on their own bottom-up management strategies [START_REF] Klassen | Top-down and bottom-up water management: A diachronic model of changing water management strategies at Angkor, Cambodia[END_REF]. Interestingly, social constraints regarding land sales and a reduction of tax immunities on temple foundations (especially 10th through early 12th century CE taxation) seems to have slowed the growth of the AMA beginning in the 11th century CE, as land in these regions was increasingly consolidated into the hands of elites. It is also likely that environmental factors and the landscape's carrying capacity limited settlement expansion [START_REF] Hawken | Designs of kings and farmers: Landscape systems of the greater Angkor urban complex[END_REF][START_REF] Lustig | Water and the Transformation of Power at Angkor, 10th to 13 th Centuries A[END_REF]Pottier, 2000b).

Overall population growth in both the AMA and CCC was slow during the 12th century CE, but our model supports conventional Angkorian scholarship in placing Angkor's apogee (sensu [START_REF] Feinman | The scale, governance, and sustainability of central places in Pre-Hispanic Mesoamerica[END_REF] during Period 5 in the late 12th to early 14th centuries CE when at least 688,0000 and perhaps as many as 900,000 lived in the Greater Angkor Region. Jayavarman VII's reign seems to have spurred asignificant increase in population density in the CCC. Major works in the polity's capital included a series of state temples and the walled enclosure of Angkor Thom under Jayavarman VII. However, in the period after Jayavarman VII's death, elites likely began to abandon the CCC, prompting socio-political, religious, and environmental changes that reduced population across much of the Greater Angkor region, although the exact scale of this is currently unknown.

This study makes several contributions to our understandings to the growth of agro-urban centers and urbanism more broadly. Firstly, the Angkorian case study suggests centralized state control is not a necessary determinant for urban expansion. On the one hand, the development and increased density of Angkor's civic-ceremonial zone were shaped by Angkorian rulers and their entourages, both through intentional acts like state projects and unintended consequences like the growth of an elite "middle class" [START_REF] Fletcher | Trajectories to low-density settlements past and present: paradox and outcomes[END_REF][START_REF] Smith | Urbanism and the middle class: Co-emergent phenomena in the world's first cities[END_REF]. Developments in the AMA, in contrast, involved local decisionmaking and governance and did not simply reflect exploitation by capital elites (e.g., [START_REF] Abrams | A model of fluctuating labor value and the establishment of state power: An application to the Prehispanic Maya[END_REF][START_REF] Klassen | Top-down and bottom-up water management: A diachronic model of changing water management strategies at Angkor, Cambodia[END_REF][START_REF] Hirth | Economic consumption and domestic economy in Cholula's Rural Hinterland, Mexico[END_REF][START_REF] Small | Factoring the countryside into urban populations[END_REF][START_REF] Steinkeller | City and countryside in third-millennium southern Babylonia[END_REF][START_REF] Taylor | Roman urbanism: A view from the countryside[END_REF]. Aspects of Angkor's political economy are similarly heterogeneous. The production of stoneware ceramics was relatively decentralized and use of these ceramics was widespread across the Angkor empire [START_REF] Grave | Centralized power/decentralized production? Angkorian stoneware and the southern production complex of Cheung Ek, Cambodia[END_REF][START_REF] Grave | Differentiating khmer stoneware production: An NAA pilot study from Siem Reap Province, Cambodia[END_REF]. However, the production and use of objects associated with temples such as decorative lintels, bronze statues, and even the iron used in the construction of temples, was more centralized and under state control [START_REF] Hendrickson | Sparks and needles: Seeking catalysts of state expansions: a case study of technological interaction at Angkor, Cambodia (9th to 13th centuries CE)[END_REF][START_REF] Polkinghorne | Decorative Lintels and Ateliers at Mahendraparvata and Hariharālaya[END_REF][START_REF] Polkinghorne | Casting for the King: The Royal Palace bronze workshop of Angkor Thom[END_REF][START_REF] Polkinghorne | Carving at the Capital: A stone workshop at Hariharālaya, Angkor[END_REF].

Secondly our work shows that both agrarian potential and individual ruler policies may limit urban size and configuration. Until the late 12th century, Angkor's growth stayed within the carrying capacity of the landscape. Even then, the upper range of our population estimate during this period (approx. 900,000 people) is based on intensive habitation on the embankments, which is thus far untested. However, the growth of Angkor over time was "pushed" by the activities of particular rulers who expanded Angkor's borders and infrastructure. This resulted in variable growth in the CCC and AMA over time. The relationship between the CCC and AMA communities was likely a critical factor in Angkor's urban longevity. As has been noted for other agro-urban settlements, the CCC's integration with the AMA and BANKs zones could have allowed for access to diverse ecological resources leading to urban sustainability; recent work has pointed out that "the Khmer did not live on rice alone" [START_REF] Castillo | The Khmer did not live by rice alone: Archaeobotanical investigations at Angkor Wat and Ta Prohm[END_REF]; see also [START_REF] Castillo | Life goes on: Archaeobotanical investigations of diet and ritual at Angkor Thom, Cambodia (14th-15th centuries CE)[END_REF][START_REF] Scarborough | Distributed urban network systems in the tropical archaeological record: Toward a model for urban sustainability in the era of climate change[END_REF]. A ritual economy linking the AMA temple communities with those in the core may have also facilitated Angkor's long-term sustainability. Work at Teotihuacan, for example, has suggested that public rituals were key to maintaining long-term unity within the multicultural population [START_REF] Filini | Teotihuacan: Ritual economy, exchange, and urbanization processes in classic period mesoamerica[END_REF]. We expect that people in AMA communities likely came into the CCC to participate in ritual festivals and royal performances [START_REF] Stark | Southeast Asian urbanism: from early city to classical state[END_REF]. Migration was an important component of ancient urbanism (Smith, 2014a;Smith, 2014b;[START_REF] Storey | Introduction: Urban demography of the past[END_REF]. As noted earlier, temple inscriptions suggest that some smaller temples had cyclical labor forces. Could similar workgroups be moving into and out of the state temples within Angkor's CCC? Future studies could estimate, for example, the labor needed to expand Jayavarman VII's CCC (see [START_REF] Kim | Lasting monuments and durable institutions: Labor, urbanism, and statehood in Northern Vietnam and beyond[END_REF][START_REF] Smailes | Building Chan Chan: A project management perspective[END_REF]. Such work might also shed light on how Angkorians crafted their shared identity and how AMA communities may have been integrated into or resisted the Angkorian state (e.g., [START_REF] Buell | The rise of a Minoan City and the (re)structuring of its hinterlands: A view from Galatas[END_REF][START_REF] Smith | Early walled cities of the Indian subcontinent as small worlds[END_REF][START_REF] Yaeger | The social construction of communities in the classic Maya Countryside: Strategies of affiliation in western Belize[END_REF].

Angkor's massive settlement complex was neither an accident nor entirely planned, but it was certainly created (Cowgill, 2004: 535). That Angkor was able to maintain its dominance for hundreds of years also testifies to the sustainability and stability of this urban form [START_REF] Klassen | Top-down and bottom-up water management: A diachronic model of changing water management strategies at Angkor, Cambodia[END_REF][START_REF] Scarborough | Distributed urban network systems in the tropical archaeological record: Toward a model for urban sustainability in the era of climate change[END_REF][START_REF] Stark | Universal rule and precarious empire: Power and fragility in the Angkorian State[END_REF]. As discussed above, multiple factors influence the development of agro-urban settlements. This fine-grained analysis allows us to see more clearly how and when these factors facilitated the development of the Greater Angkor region. While many of these took place within a local historical context, we argue that future comparative studies might observe similar patterns.

CRediT authorship contribution statement

Alison

Fig. 1 .

 1 Fig. 1. The 3000 square kilometer area of Greater Angkor, including the upland region of Phnom Kulen, and the 10th century CE capital of Koh Ker.

Fig. 3 .

 3 Fig. 3. Lidar imagery of (A) Angkor Wat and (B) a temple community with a classical prasat-trapeang formation in the AMA. The two areas are shown at the same scale to emphasize the much larger size of the state temples in the CCC compared to the smaller size of the temples in the AMA.

Fig. 4 .

 4 Fig. 4. Population growth over time.

Fig. 5 .

 5 Fig. 5. Population density in the AMA and CCC zones over time.

  Kyra Carter: Conceptualization, Methodology, Investigation, Writing -original draft, Writingreview & editing. Sarah Klassen: Conceptualization, Methodology, Investigation, Writing -original draft, Writing -review & editing, Visualization. Miriam T. Stark: Investigation, Writing -review & editing. Martin Polkinghorne: Investigation, Writing -review & editing. Piphal Heng: Investigation, Writing -review & editing. Damian Evans: Investigation, Writing -review & editing. Rachna Chhay: Investigation, Writing -review & editing.

The 30km2 area represents the main location of Yaśodharapura. If the earlier capital of Hariharālaya is included, the total area is closer to 75km2

To date features such as embankments, mounds, and ponds in the CCC, which typically do not have inscriptions, we used several methods. In many cases we could use a relative system of grouping features with other features that either date to the same time period or date to an earlier time period. For example, if a mound was built over an embankment it is assumed that the mound was built after the embankment (seeKlassen et al., 2021 for further discussion).

Our start date for Period 1 is based on a radiocarbon date from excavations within Hariharālaya and reflects evidence for this earlier population(Pottier et al., 2005: 15;[START_REF] Penny | Vegetation and land-use at Angkor, Cambodia: a dated pollen sequence from the Bakong temple moat[END_REF]. This date is somewhat arbitrary; as our focus is on developments from the 9th century CE period, we use the 770 CE date to partially capture the earlier phase at Hariharālaya.

Acknowledgements

The Authors thank the APSARA National Authority for their permission to conduct remote sensing and field investigations. Thanks also to Roland Fletcher for his support. Thank you to Terry and Eileen Lustig for their comments and suggestions on aspects of economic geography and Michael E. Smith for reading and offering comments on an earlier draft of this paper. Thanks to Malay So and Maryne Dana for administrative support. Funding Research, planning, and writing of this manuscript was undertaken with the support of the University of Oregon Global Oregon Faculty Collaboration Fund supported by the Global Studies Institute in the UO Office of International Affairs. Data collection for parts of the research in this study have been funded by: the National Geographic Society Committee for Research and Exploration under Grant 9602-14; Dumbarton Oaks under a Project Grant in Garden and Landscape Studies; the Social Sciences and Humanities Research Council of Canada Postdoctoral Fellowship; the National Science Foundation Doctoral Dissertation Research Improvement Awards (#1638137); Australian Research Council Discovery Early Career Researcher Award (DE150100756) and Council Discovery Grant (DP170102574); and the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreements 639828 and 866454).