Justin Badeau
email: badeau@endemys.com

Frédéric Guibal

Peter Z Fulé

Sandrine Chauchard

Pasquale Moneglia

Christopher Carcaillet
email: christopher.carcaillet@ephe.psl.eu

years of fire regime in Corsica 1 202 years of changes in Mediterranean fire regime in Pinus nigra forest, Corsica

Keywords: climate, dendrochronology, fire frequency, fire season, fire area, fire scars, land 42 use, management, mountain, Pinus nigra laricio, tree-ring

Wildfires are critical socio-ecological features in the Mediterranean basin. In a context of global changes (climate, land use), we questioned whether the wildfire regime was altered in the mountains of Corsica, France. Using tree-ring analysis of fire-scarred trees, we tested for changes in frequency, seasonality, area. We hypothesized that the fire regime changed during the middle-20 th century due to human activities, as observed elsewhere in the Mediterranean.

We sampled fire-scarred trees, geolocated for mapping fire areas, in a forest of black pine (Pinus nigra laricio). The oldest fire was in 1684 but the fire chronology with adequate sample depth for analysis covered 202 years . Between 1820-2012, 15 fires were recorded, 8 of which scarred at least 25% of the sampled trees. The mean fire interval was 14 years, corresponding to a high fire frequency with 4 major fires per century. Most fires occurred between 1931-1970. On average, about 50% of trees were scarred by fires before 1931, but this percentage decreased thereafter. The exception was the 2000 fire that impacted 100% of living trees. Mapping showed spatially heterogenous fire areas. These results match other Mediterranean studies showing longer fire intervals since the late-20 th century, and wildfires generally occurred during the period of late-earlywood or latewood formation, i.e., summer or early autumn, which is the season of contemporary fires. Although fires were recurrent for more than 200 years with no change in the fire season, the regime changed twice in frequency. These changes likely result from a combination of land use and warmer summer conditions. While pines survived most past fires of low intensity through the last large fire in the 1970's, the severe fire of 2000, following ca 30 years of fire suppression, killed large patches of mature trees. Such chronology provides rational arguments for black pine ecosystem management, notably to consider seeking to recover the sustainable fire regime of the 19 th century, for instance by using prescribed fires to manage surface fuel.

Introduction

Wildfire is a key component of ecosystem functioning at global scale [START_REF] Bond | Fire as a global 'herbivore': The ecology and evolution of flammable ecosystems[END_REF][START_REF] Sayedi | Assessing changes in global fire regimes[END_REF]. The ecological roles of wildfire depend on fire regime parameters such as fire intervals, intensity, and seasonality, which are related to the frequency, extent, and severity of fires [START_REF] Johnson | Fire and vegetation dynamics: studies from the North American boreal forest[END_REF][START_REF] Keeley | Fire intensity, fire severity and burn severity: A brief review and suggested usage[END_REF]Pausas and Ribeiro, 2013). Globally, fire regime shifts are driven by complex interplays between climate and land uses as reported in Mediterraneanclimate areas of Australia, Europe and North America [START_REF] Moritz | Learning to coexist with wildfire[END_REF] and at a global scale as well [START_REF] Andela | A human-driven decline in global burned area[END_REF]. Because fire regimes are under control of both climate and land uses over millennia, they are thus a socio-ecosystems component (sensu [START_REF] Liu | Complexity of Coupled Human and Natural Systems[END_REF], resulting from coupled natural and social drivers, including legacies of past conditions, producing multivariate responses of fire behaviour (e.g., Niklasson and Granström, 2000;[START_REF] Guiterman | Spatiotemporal variability of human-fire interactions on the Navajo Nation[END_REF].

The Mediterranean Basin is fire prone due to dry and warm summers, as well as fire-adapted native species [START_REF] Pausas | Are wildfires a disaster in the Mediterranean basin? -A review[END_REF]. Climate models predict that the late-21 st century will be warmer and drier, including in winter, leading to more fire years and a broader fire season in the region [START_REF] Ozturk | Projections of climate change in the Mediterranean Basin by using downscaled global climate model outputs[END_REF][START_REF] Turco | Exacerbated fires in Mediterranean Europe due to anthropogenic warming projected with non-stationary climate-fire models[END_REF]. Mediterranean ecosystems of southeastern France have already experienced changes in fire regimes since the 1970's through the mid-1990's, with more burned areas and higher yearly and seasonal fire occurrences [START_REF] Fréjaville | Spatiotemporal patterns of changes in fire regime and climate: defining the pyroclimates of south-eastern France (Mediterranean Basin)[END_REF]. However, since 1986 [START_REF] Ruffault | How a new fire-suppression policy can abruptly reshape the fire-weather relationship[END_REF] or the mid-1990's [START_REF] Fréjaville | Seasonal changes in the human alteration of fire regimes beyond the climate forcing[END_REF], the trend has changed suggesting a partial disconnection between fire regime and climate, or the effects of other drivers such as policies of land management. Similar trends have been recorded in other Mediterranean countries such as Spain (Pausas and Fernandez-Munoz, 2012), although not in north Africa [START_REF] Chergui | Socioeconomic Factors Drive Fire-Regime Variability in the Mediterranean Basin[END_REF]. Reconstructing and decomposing long-term fire regime characteristics (frequency, season, areas) remains helpful for forest managers to constitute baselines for analyzing current trends in light of past recent regimes.

In the Mediterranean basin, black pine (Pinus nigra Arnold) is common in many countries where it is a dominant tree, considering that its large biomass drives most ecosystem processes (the mass ratio hypothesis sensu [START_REF] Grime | Benefits of plant diversity to ecosystems: immediate, filter and founder effects[END_REF]. Black pine has been also abundantly planted since late 19 th century (hereafter c.) for timber production and soil protection, resulting globally in 3.5 million hectares of new forests [START_REF] Isajev | EUFORGEN Technical guidelines for genetic conservation and usefor European black pine (Pinus nigra)[END_REF] sometimes for assisted migration [START_REF] Michalet | Assisted migration in a warmer and drier climate: less climate buffering capacity, less facilitation and more fires at temperate latitudes? Oikos[END_REF]. Its management in the face of climate and fire changes would benefit from more precise baselines on historical fire regime of this region over time. Detailed baselines on historical fire regimes in P. nigra forests have started to emerge [START_REF] Fulé | Forest structure and fire history in an old Pinus nigra forest, eastern Spain[END_REF][START_REF] Christopoulou | Dendrochronology-based fire history of Pinus nigra forests in Mount Taygetos, Southern Greece[END_REF]Sahan et al., 2022), providing site-and time-specific reconstructions of past fires. All these studies showed that fire intervals were shorter during the late-19 th or the early-20 th c., and that the fire intervals became longer in the late-20 th c. Generally, in Europe and the Mediterranean basin, the 19 th c. was a period of intense rural and forest land uses for domestic herding and wood production [START_REF] Grove | The nature of Mediterranean Europe: an ecological history[END_REF]. Such intense usages could explain the more frequent fires during the 19 th c., despite a cooler climate [START_REF] Büntgen | Filling the Eastern European gap in millennium-long temperature reconstructions[END_REF][START_REF] Luterbacher | European summer temperatures since Roman times[END_REF]. However, the generalized land-use abandonment in the Mediterranean, varying somewhat among countries and regions [START_REF] Chauchard | Patterns of land-use abandonment control treerecruitment and forest dynamics in Mediterranean mountains[END_REF][START_REF] Roman Sanz | Long-term forest dynamics and land-use abandonment in the Mediterranean mountains, Corsica, France[END_REF][START_REF] Fortuny | Land use legacies and site variables control the understorey plant communities in Mediterranean broadleaved forests[END_REF], altered risks of ignition. At the turn of the 21 st c., global warming enhanced a trend for more severe fires, indirectly fostered by land-use abandonment that triggers fuel build-up at stand scale and forest connectivity at landscape scale [START_REF] Ganteaume | What causes large fires in Southern France[END_REF]Jappiot, 2013, Mouillot et al., 2003).

A growing body of dendrochronological literature reported extensive surface fire in P. nigra massifs around the Mediterranean [START_REF] Fulé | Forest structure and fire history in an old Pinus nigra forest, eastern Spain[END_REF][START_REF] Christopoulou | Dendrochronology-based fire history of Pinus nigra forests in Mount Taygetos, Southern Greece[END_REF][START_REF] Camarero | Past growth suppressions as proxies of fire incidence in relict Mediterranean black pine forests[END_REF]Sahan et al., 2022). However, Corsica is still an area of gap of knowledge on fire regime, except for a multimillennial study based on sedimentary charcoal [START_REF] Leys | Historical range of fire frequency is not the Achilles' heel of the Corsican black pine ecosystem[END_REF] reporting that fire was closely associated to black pine for more than 12,000 years. [START_REF] Szymczak | A dendroecological fire history for central Corsica/France[END_REF] carried out a fire study based on tree-ring analysis of 10 fire-scarred cross-sections supplemented by increment cores and an administrative-based study in lowland forest of oaks and maquia was published by [START_REF] Mouillot | Long-term forest dynamic after land abandonment in a fire prone Mediterranean landscape (central Corsica, France)[END_REF]. Therefore, the present study aims to test the hypothesis that the fire frequency has changed since the 19 th c in forests of Pinus n. subsp. laricio (Poir.) Maire (hereafter P. nigra). The study is based on dendrochronological analysis of fire scars [START_REF] Arno | A method for determining fire history in coniferous forests of the Mountain West[END_REF][START_REF] Zackrisson | Influence of forest fires on the north Swedish boreal forest[END_REF][START_REF] Huffman | Fire regimes and structural changes in oak-pine forests of the Mogollon Highlands ecoregion: Implications for ecological restoration[END_REF].

On the 27 th August 2000, a substantial area of lethal crown fire occurred near Vizzavona (central Corsica), reported to have burned a total of 3900 ha, i.e., 10% of black pine cover in Corsica. We selected this site to determine if fire regime has changed significantly during past centuries, and if there is evidence of drivers supporting the eventual change in fire regime in an area that experienced changes in its human demography. The main objective of the present study is to reconstruct the longest fire chronology, the temporal, seasonal and spatial variability in this central Corsican forest and, to a lesser extent, explore possible links between human demography and fire activity. We hypothesized that changes in fire regime were linked to local trends in human demography, and fire season was stable, occurring during the warm/dry summer season (climate driver). All these fire parameters will be helpful to establish the historical range of variability of fire regime useful to delineate baselines of Corsican black pine forest management.

Materials and methods

Study site

Corsica is a French Mediterranean island, located west of the Italian peninsula and southeast of southeastern mainland France (Figure 1a). Corsica is mountainous with several summits above 2000 m above sea level (a.s.l.). The study site, hereafter the "Vizzavona forest", is situated in central Corsica (42.14 N,9.19°E). It corresponds to the state forest of Rospa-Sorba, and the two communal forests of Vivario and Muracciole, all mostly used for timber production, but not where the sampling was carried out. There are few semi-feral cattle extensively grazing in the study forest. One shepherd sometimes uses the forest for his goats. Vizzavona forest is also an emblematic site with high touristic and patrimonial value, located at the junction between north and south parts of the island. The bedrock is composed of igneous rocks or granites. Vizzavona forest soils are 35-65 cm deep brunisols, slightly acidic (pH: 5.5 to 6.5) sandy-silty, respectively 60% and 40% of sands and silts (IFN report 2004), resulting a low water storage. At Vizzavona, the climate is Mediterranean with hot summers and cool winters, but the orography results in cold seasonal conditions, notably in winter with 4 to 5 months of intermittent snow cover. During the 1990-2020 period (nearest weather station at 772 m a.s.l.; 42.152608°N, 9.149188°E), mean annual precipitation was 1265 ±291 mm with a mean annual temperature of 9 ±0.6°C. Mean monthly minimum precipitation and maximum temperatures were both recorded in July (32 ±3.6 mm; 17.8 ±2.9°C) and August (33 ±3.2 mm; 17.7 ±2.8°C).

Mean monthly precipitation peaked in November (208 ±16.4 mm), including snowfall, and monthly minimal average temperatures occurred in February (1.9 ±3.5°C).

Regarding wildfires in Corsica, the Prométhée fire database between 1973-2022 (https://bdiff.agriculture.gouv.fr/) indicates that 55% of fires occurred between July and September, including 39% in July and August (Supplementary Information Figure S1); 95% of total area burned between July and September, especially between July and August (86%). In black pine forests, the main fuel is composed of shrubs, i.e., Erica arborea below 1400 m a.sl.

(max. 3-m tall) and Juniperus sibirica Lodd. Ex-Burgsd from 1400 to 1600 m a.s.l. (< 1-m), saplings of pines, a thick litter layer of pine needles, and woody debris (Figure S2).

Material

In Corsica, black pine covers 372 km² (Figure 1a) mostly above 1000 m up to 1800 m a.s.l.

Its lifespan is potentially over 800 years [START_REF] Szymczak | Combining wood anatomy and stable isotope variations in a 600-year multi-parameter climate reconstruction from Corsican black pine[END_REF]. P. nigra needs a strong annual precipitation (800 to 1200 mm.yr -1 ) but supports dry summers and colonize soils with low water storage capacity. Trees can reach 40 m in height. They have a thick bark and a high crown base protecting adult trees from fires (Fréjaville et al., 2018b). Because it does not have serotinous cones, seedling regeneration is limited after severe fires [START_REF] Pausas | Are wildfires a disaster in the Mediterranean basin? -A review[END_REF].

Field sampling

We selected six plots within the study area (Figure 1b) according to three main parameters:

(i) presence of large black pines (assumed old trees) to sample multi-scarred trees and maximize the probability to obtain the longest fire chronology; (ii) areas characterized by a dense treecover of Pinus pinaster or Fagus sylvatica were excluded because they both present different flammability traits (Fréjaville et al., 2018b) and niche (Fréjaville et al., 2018a); (iii) due to severe relief, plots needed to be close to paths for transport of sampling equipment and wood samples. Mean plot slopes ranged from 45 to 80%, and aspect varied from north to west, following an altitudinal gradient ranging from 1000 m to 1400 m. (Table 1). Plots were relatively homogeneous with respect to topography and vegetation between and within them.

Depending on the plot, there could be regeneration of P. nigra only, or both P. nigra and P. pinaster (VZ02); in more open areas, there was dense cover of tree heather (Erica arborea L.; VZ03). We selected trees presenting the highest number of visible scars on living trees, stumps, logs or snags to establish a thorough fire history [START_REF] Farris | A comparison of targeted and systematic fire-scar sampling for estimating historical fire frequency in south-western ponderosa pine forests[END_REF]. We used chainsaws to remove small samples of wood from standing trees (living or dead), partial cross-sections that represented <10% of a tree's cross-sectional area, a sampling approach that presents minimal risks of tree breakage [START_REF] Heyerdahl | Condition of live fire-scarred ponderosa pine eleven years after removing partial cross-sections[END_REF]. Samples were labeled and wrapped with plastic film for transport to the lab. For every sample, we measured diameter at breast height (~1.3 m), latitude, longitude, elevation, slope, slope aspect, aspect of the scar, and the number of suspected scars. Each sample was photographed.

Further, we sampled ten unscarred old trees in the VZ05 plot using increment borers to develop tree-ring chronologies on trees that were obviously not scarred, helpful for cross-dating and for comparison in addition to a reference chronology of P. nigra, extracted from the International Tree-Ring Data Bank (www.ncei.noaa.gov/access/paleo-search/study/4389; author : Schweingruber, 2002). For this purpose, two cores were sampled per tree at 1.3 m height, one on the uphill side of the trunk and one at a 90° angle."

Tree-ring crossdating and fire scar dating

In the lab, wood samples were air-dried for at least one month, then sanded with progressively finer grits from P40 to P400, to obtain a smooth surface with cells visible under microscopes (×100) [START_REF] Stokes | An introduction to tree-ring dating[END_REF]. After surfacing, we digitized samples using an A3-format scanner EPSON expression 12000XL at 1200 dpi. We crossdated series with the reference chronology visually and with graphical assistance from CDendro© (Cybis.se) software [START_REF] Maxwell | Measuring tree-ring widths using the CooRecorder software application[END_REF]. Ring-widths were measured of scanned images in Coorecorder© software (Cybis.se) and we used Cofecha software [START_REF] Holmes | Computer-assisted quality control in tree-ring dating and measurement[END_REF] to carry out quality control of crossdating.

The Schweingruber ring-width chronology (FRAN027) covered the period AD 1518 to 1980 (Figure S3). We measured and crossdated cores from living unscarred pines then we added them to Schweingruber's reference chronology in order to update the chronology to 2021

(Figure S3). The new chronology was used to crossdate scarred trees. The R package dplR [START_REF] Bunn | A dendrochronology program library in R (dplR)[END_REF]) was used to calculate dendrochronological statistics of this chronology (master series length, series intercorrelation, mean sensitivityetc.).

We identified fire scars to the year and seasonal position within tree-rings using the designations of [START_REF] Baisan | Fire history on a desert mountain range: Rincon Mountain Wilderness, Arizona[END_REF]: dormant season (D), earlywood (EE), midearlywood (ME), or late-earlywood (LE) and latewood (LW). The code U for undetermined was used to specify when we could not locate the scar position in the ring, usually in the case of very narrow rings, decayed or fragmented samples (when scars are located at cracks). Pinus nigra growth starts in mid-April when temperatures are increasing coupled with available water (rain or melted snow). Growth slows in June and can be interrupted in early July when temperatures become too high and dryness too severe (Haüsser et al., 2021). Thus, we defined the dormant season as the period between autumn and the following spring. Based on the overwhelming prevalence of summer to early-autumn fires reported in black pine forest since 1973 when the French national fire database, Promethee, began (www.promethee.com), we assumed that dormant-season scars primarily formed in the late summer (August) or early autumn (September). However, we cannot rule out wildfires in spring or in winter prior to earlywood formation if conditions of ignition (lightning or people) and spread (dryness) were appropriate in winter; occurrences of winter fires have increased since the 1990's [START_REF] Fréjaville | Spatiotemporal patterns of changes in fire regime and climate: defining the pyroclimates of south-eastern France (Mediterranean Basin)[END_REF].

We plotted composite fire chronologies for each plot beginning with the first fire event with a minimum of 2 recording samples. We also inventoried fire dates according to two different thresholds (25 and 50%) resulting in three classes of affected trees or severity: fire year affecting less than 25% of scarred samples, fire years affecting between 25 and 50% of scarred samples and fire years affecting 50% or more scarred samples.

Mapping

For mapping scarred trees, coordinates of each sample were measured with a Garmin GPS through the World Geodetic System 84 (WGS84) providing a positioning accuracy of 3-5 m.

The plot areas were retrospectively estimated from GIS locations of sampled trees by defining a 100 m buffer zone around each geolocated tree. It is common to map locations of trees scarred by specific fires as an estimate of the spatial extent of fire [START_REF] Farris | Spatial and temporal corroboration of a fire-scar-based fire history in a frequently burned ponderosa pine forest[END_REF]. When samples have been collected over a systematic grid, maps based on Thiessen polygon tessellations have been shown to provide accurate reconstructions [START_REF] Farris | Spatial and temporal corroboration of a fire-scar-based fire history in a frequently burned ponderosa pine forest[END_REF]. In the case of irregularly distributed samples, however, Thiessen polygons may create unusual shapes that are artifacts of the technique. Therefore, we estimated burned areas using a neutral kriging approach [START_REF] Fulé | Fire regimes over a 1070-m elevational gradient, San Francisco Peaks/Dook'o'oosłííd[END_REF], i.e., quadratic Kernel densities, called the "heatmap" tool in QGIS. We developed a map for each fire year. Densities of probabilities were calculated based on a spreadsheet containing binary values for each dated sample: 1 for fire year, and 0 without fire. Kriging parameters are explained in SI, section 4 and figure S4.

We merged all probability density functions for all fire years to provide a general probability of past fire occurrences corresponding to the reconstructed fire history. Probability densities were weighted by the total number of scars for each dated sample. This map makes it possible to estimate the wildfire pattern at the landscape level.

Note that the interpretations of burning probability are only accurate between plots and are contingent on the selection of plot locations. Thus, the kriged maps are useful for relative comparisons between fire years, but do not provide landscape-scale fire probability information.

Human demography data

We evaluated human demography as a proxy of land uses. and 1820. For the present study, we extracted data for all of Corsica for the general trend, as well as the local trends reported for the village of Vivario (located on the northwest slope of Sorba pass), and for the village of Ghisoni (located on the southeast slope of Sorba pass). We also compared the dates of fires with historical events of World War 2 (WW2).

Data analysis

We used the R package burnr [START_REF] Malevich | burnr: Fire history analysis and graphics in R[END_REF] to calculate fire regime metrics for each plot such as composite fire return intervals (FI), their arithmetic mean (MFI), median (median FI), and the Weibull median probability interval.

Regarding FIs, we tested based on the two-samples Wilcoxon rank sum test whether they were significant differences of mean burned areas and fire frequencies between periods characterized by change point assumed tipping point. This method was used as fire intervals per period were small (n < 10) and non-parametric methods better suit this type of dataset than t-tests requiring normal distribution and larger sample size.

The Weibull calculation (eq. 1) provides the c parameter, which characterizes the shape of the

Results

On average, 11 trees were sampled per plot, ranging from 8 to 14 (Table 2). A total of 64 scarred samples was collected in the Vizzavona forest, totaling 196 dated fire-scars, in a total survey area of 43 ha (Table 1).

The ring-width chronology we constructed by updating Schweingruber´s original FRAN027 chronology contained 30 series and covered the period 1518 to 1980. The overall correlation (rbar) was 0.57, mean sensitivity0.21, and EPS 0.96.

Fire records

Out of the 64 samples collected, 48 were successfully crossdated (75%), resulting in a mean of 8 crossdated samples per plot (Table 2). The samples that could not be crossdated were generally due to too much decayed wood (due to fungi or ants) or samples composed of too many broken sections leading to unusable series containing not enough number of rings. Our whole chronology covered a 390-year period, from 1631 to 2021. The oldest fire was dated to 1684 (VZ06) and the first fire present on more than one tree occurred in 1820. From 1820 onward, the 196 fire-scars recorded corresponded to 15 fire years (Figure 2). Fire interval analyses were calculated beginning from the first fire year with a minimum of 2 samples recording fire events. The common period for analysis was thus 1820-2021 (202 years).

Our chronology and associated frequency changes partly matched administrative records (Promethee, ONF, OEC databases, period 1950-2019). Two fire events were found in both fire records and the fire scars (1970 and 2000) while others, such as the 2012 fire in VZ04, were identified by dendrochronology only (Figure 2).

Fire interval analysis

Between 1820-2021, a total of 15 fires was reported among the different plots covering 43 ha in total (Figure 2). The minimum fire interval per plot was 3 years (VZ02) and the maximum was 86 years (VZ06; Table 3). At the scale of the study site (43 ha), the minimum interval between two occurrences was 2 years, and the maximum was 46 years (Table 3). The mean fire interval (MFI) of 14 (±13) years is close to the median interval of 12.0 years and the Weibull median probability interval of 10.7 years as well. Eight fires affected at least 25% of sampled trees in 1820, 1866, 1881, 1906, 1918, 1931, 1943 and 2000. Considering this filter, minimum and maximum FI were 12 and 57 years respectively, MFI of 26 ±19 years and Weibull median probability interval of 23.2 years (Table 2). Five fires affected at least 50% of recorded samples (1820,1881,1906,1918,2000) with a minimal FI of 12 years, a maximum of 82 years, a mean (±sd) of 45 ±32 years and a Weibull median probability interval of 40 years. Regarding the 8 major fires (>25% of samples with fire-scars), all occurred before 1943, except the one of 2000. The FI trend shows that three significant fire periods occurred over the past 202 years (figure 3a): 3). We also tested if the end of the second world war in 1945 could be a tipping point. We found that fire frequencies were not different before and after this year in the Vizzavona forest, i.e., MFI 16 ±14 yrs versus 11 ±10 yrs (Wilcoxon test: p = 0.65).

Fire season

Fire season could be identified on 72% of the fire scars, i.e., 142 out of 196. We found that 71% of scars were formed during latewood (55%), late earlywood (2%) or the dormant season (14%), i.e., during the summer to autumn seasons (Figure 4). We identified 2% of scars in midearlywood and no scars in earlywood (dataset available in Table S1).

Fire extent

Kriging-based reconstructed areas for each of the 15 fire years recorded (Figure 5a) shows that in the case of major fires, probability densities of buffers were connected because a large part of the area experienced a common fire year, whereas in the case of minor fires, one or a few plots were affected. We also calculated the percentage of burned surface over total sampled area burned by fire year (Figure 3b; values in Table S2). However, the oldest fire of 1820 was only encountered in plot VZ06; because trees were not yet recruited in other plots, it is not possible to determine if the 1820-fire was large enough to affect other plots. Therefore, the area of the 1820-fire is a minimum area and must be considered with caution.

When we consider burned surfaces, we observe a difference between the Based on the merging of all the 15 fire years and the probability density assessment, it appears that two main locations burned more frequently in the past (Figure 5b): first the VZ01 area corresponding to a slope exposed to northwest and second, in the east, the VZ05 area, in the northwest of the Sorba Pass, on the top of a talweg. The southwestern part of the study area (plots VZ03 and VZ04) is an area where fewer past fires burned, even though the 2000 fire spread there, but at lower severity. From personal observations, this southwestern part is intermingled by small stream (grey dashed line on Figure 5b), and a few beeches (F. sylvatica, less flammable species).

Discussion

Like other P. nigra forests in the Mediterranean basin, the Corsican black pine forest of Vizzavona was frequently subject to fire events since the 17 th century (Figure 2). In Greece, oldest evidence of fire scars was dated of 14 th c. [START_REF] Touchan | Fire history in European black pine (Pinus nigra Arn.) forests of the Valia Kalda, Pindus Mountains, Greece[END_REF], whereas in Anatolia they were from 16 th c. (Sahan et al., 2022). However, the established variability in frequency and severity at Vizzavona covers the last 202 years, from 1820 to 2012, i.e., first and last events (Table 4). Wildfire regimes have changed in frequency at least twice since 1820. Finally, the most recent fire in Vizzavona, in 2000, was much more severe than all the previously recorded fires that were characterized by numerous surviving scarred trees. This knowledge of fire regimes is useful for land and forest managers, whether it is to plan fire control policies [START_REF] Alcasena | Towards a comprehensive wildfire management strategy for Mediterranean areas: Framework development and implementation in Catalonia, Spain[END_REF] or in ecosystem management that bases sustainable forest management on natural disturbance regimes through Nature-Based Solution processes [START_REF] Gauthier | Ecosystem Management in the Boreal Forest[END_REF].

Table 4. Synthesis of fire regimes in natural black pine forests in the Mediterranean basin, inferred from fire-scars and tree-ring analyses; studies are presented from west to east; fire frequency was calculated only on major fires, which are those that scarred 25% of trees, over the 19 th , 20 th and 21 st centuries that is the comparable covered period of all studies.

A 202-year chronology with changes in fire frequency

The Corsican chronology cover 202 years, similar in coverage with the studies in southern Greece [START_REF] Christopoulou | Dendrochronology-based fire history of Pinus nigra forests in Mount Taygetos, Southern Greece[END_REF]) and eastern Spain [START_REF] Fulé | Forest structure and fire history in an old Pinus nigra forest, eastern Spain[END_REF]. The only longer chronology is the one in Anatolia with 553 years (Sahan et al., 2022). In total, we found 15 fire years in 193 years, including 8 major fires that result a frequency of 4.1 major fires per 100 years (Table 4). These values are little lower than those found elsewhere in the Mediterranean basin since the 19 th century: 5.9 fires.100 yrs -1 in Anatolia, 6.7 fires.100 yrs -1 in Greece; in Spain, 6.4 fires.100 yrs -1 is also close to the general trend if, in this case, we consider all fire events and not major fires only (Table 4). The comparison of fire intervals with the other studies in Corsica [START_REF] Szymczak | A dendroecological fire history for central Corsica/France[END_REF] or Greece [START_REF] Touchan | Fire history in European black pine (Pinus nigra Arn.) forests of the Valia Kalda, Pindus Mountains, Greece[END_REF] was not possible as they did not explore this aspect in depth, since they had a limited number of sampled trees, or only one scar per fire. The Mediterranean-wide results correspond to an average frequency of one major fire every 18 years in black pine forests since the beginning of 19 th c., meaning that the overall mean frequency has been high during the past centuries.

However, the fire frequency changed twice at Vizzavona, first during the 1930's and second after 1970 (Figure 3a). Between 1931 and 1970, the frequency was high, characterized by a short MFI of 6 ±4 years [2-14 years], while it was 22 ±14 from 1820 to 1930 (Table 3). In Anatolia, the fire frequency has also changed twice over the last 200 years, first around 1852 corresponding to an increase in frequency and then in 1934 with a drop in frequency (Sahan et al., 2022). In Spain, the frequency changed four times [START_REF] Fulé | Forest structure and fire history in an old Pinus nigra forest, eastern Spain[END_REF]. Finally, in southern Greece, the trend is less obvious; the 100-year long period before 1945 had lower frequency and the period since 1945 had an increase in frequency. The years after 1853 seemed notable both in Anatolia and Spain, corresponding to a brief period of increase in frequency. It partially matched increasing frequencies in Corsica (Figure 3a) between 1820 and 1931. This year of 1931 characterized a tipping point in our study as frequency increased from 1820 to this date (Figure 3a). During the 1930's, this trend of frequency was similar in Spain [START_REF] Fulé | Forest structure and fire history in an old Pinus nigra forest, eastern Spain[END_REF] but is the reverse in Anatolia where it corresponded to a drop in frequency (Sahan et al., 2022).

These substantial differences in timing of increasing/decreasing frequencies between studies mean that local trends cannot be upscaled to the entire Mediterranean basin; each trajectory has local drivers, because of site-specific variability (altitude, average precipitation, pastoralism, etc.) and local fire suppression policies (timing of initiation of fire suppression during the 19 th c. and level of restrictions of laws).

Potential drivers

A common pattern corresponds with the Second World War (WW2): 1943 in Corsica corresponded to severe fights the 9 th September and the 4 th October between the German forces and the Allied forces that led to the bombing of forests by German army to cover their retreat and as an act of retaliation against Corsican resistors (Ministry of Armed Forces, France: www.cheminsdememoire.gouv.fr/fr/la-liberation-de-la-corse-9-septembre-4-octobre-1943).

Similarly, in southern Greece, fire events occurred at the time of multiple battles in 1944 and 1945, burning respectively 38% of samples during the first year and 49% of samples during the second year [START_REF] Christopoulou | Dendrochronology-based fire history of Pinus nigra forests in Mount Taygetos, Southern Greece[END_REF].

After the WW2, the population began to drop in Corsica (Figure S5). The village of Ghisoni (figure 1a) followed this demographic trend, while the village of Vivario (figure 1a) followed a different trajectory as population started to fall earlier, during the 1900's (Figure S5). The timing of these two demographic decreases was different and did not coincide with change in fire frequency at Vizzavona. Furthermore, the fire frequency was not different before and after 1945 in the Vizzavona forest. This indicates that the WW2 did not change the fire frequency, and 1945 was not a tipping point. However, out of the 8 major fires, 7 happened before 1945, while only one major fire occurred after, i.e., 2000. According to [START_REF] Gilbert | Elevage, forêt et société; analyse socio-historique[END_REF], abandonment of farming lands started around 1920's-1930's and ended around the 1950's. First, abandonment of farming lands led to an increase in slash-and-burn practice to increase pastoral resources. Second, once abandonment of farming was definitely established, fire numbers decreased followed by a biomass accumulation. Thus, the weight of drivers changed between the first and second part of the 20 th c.

The Vizzavona area is a key socio-economic area in Corsica. The Sorba pass connects the center to the southeast of Corsica, whereas the Vizzavona pass connect the northeast to the southwest of the island (Figure 1). Although local population decreased, the usage of the Vizzavona area for socio-economic purposes has remains significant, and provides a source of ignition. A significant example of risk linked to the traffic is the 1970 fire which is well documented: the fire started from the roadside and spread toward the top of the slope through a talweg. Because Sorba and Vizzavona passes are important traffic points, this makes this area potentially sensitive to social-made fires.

A high fire frequency regime

Our results and those from Greece, Anatolia and Spain (Sahan et al., 2022[START_REF] Christopoulou | Dendrochronology-based fire history of Pinus nigra forests in Mount Taygetos, Southern Greece[END_REF][START_REF] Fulé | Forest structure and fire history in an old Pinus nigra forest, eastern Spain[END_REF] reveal a regime of high frequency in black pine forests whatever the country, their geographical location and cultural habits. In Vizzavona, considering all fires, the mean fire interval of 14 years corresponds to a high fire frequency (sensu Sugihara et al., 2006), with mainly surface fires. This MFI was lower than the ones from other studies: 23 years (Sahan et al., 2022), and 30 years [START_REF] Christopoulou | Dendrochronology-based fire history of Pinus nigra forests in Mount Taygetos, Southern Greece[END_REF]. However, considering only major fire years at Vizzavona, we obtained a MFI of 26 years, which remains in the category of high fire frequency. Plot number VZ06 differs from the others as the MFI is 60 years which correspond to a middle frequency.

At Vizzavona, the frequency changed twice around 1931 (increase) and 1970 (decrease),

indicating that within a short period of two centuries, there was substantial variability.

Interestingly, the data of human demography (Figure S5), show that 1931 corresponded to the start of a second drop of the Vivario population (first was in 1906), ending in 1962.

Demographic censuses of 1962 and 1968 constituted the lowest inhabitant numbers since 1800 and before the third drop in population around 2010.

Despite the different nature of samples and data compared to dendrochronology, palynological study can be complementary to understanding fire history [START_REF] Clark | Fire and climate change during the last 750 yr in northwestern Minnesota[END_REF]. Paleoecological study on the temporal variability of fire in Corsica using sedimentary charcoal and historical documents [START_REF] Camarero | Past growth suppressions as proxies of fire incidence in relict Mediterranean black pine forests[END_REF] was at millennial scale with a 20-year resolution [START_REF] Leys | Historical range of fire frequency is not the Achilles' heel of the Corsican black pine ecosystem[END_REF]. Results showed two maxima of fire frequency during the last 4500 years, attaining 0.012 fires yr -1 (1.2 fires 100 yrs -1 ; MFI of about 80 yrs). In total, the reconstructed MFI over the Holocene (12,000 years) varied between 30 and 490 years [START_REF] Leys | Historical range of fire frequency is not the Achilles' heel of the Corsican black pine ecosystem[END_REF]. These larger values might correspond to major fires knowing that charcoal peaks corresponded mainly to large and severe fires and did not probably capture low severity and small fires, which were well recorded in the present study. Further, the Leys et al study ( 2014) was based on a climatologically wetter area in western Corsica, which could explain the longer FI. The current Vizzavona study site is on the eastern side of the Corsican mountain range, and thus drier (leeward slopes, rain-shadow effect).

Flammability increased over time in both analysis periods before and after 1931 as shown by the c parameter Weibull values of 1.89 (1820-1931) and 1.48 (1931-1970). This result means that burning hazard is dependent on processes that happened between fires and not only drivers during the fire year. The reduced fire regime during the 20 th century and the long gap since the previous fire could have contributed to the severity of the 2000 fire through allowing fuel to accumulate. Such a pattern happened in Greece [START_REF] Christopoulou | Dendrochronology-based fire history of Pinus nigra forests in Mount Taygetos, Southern Greece[END_REF], where the longest interval was reported between 1973 and 2007 (34 years), resulting in fuel accumulation followed in 2007 by a severe crown fire. The policy of suppression of traditional fires in France since the king Louis XIV (AD 1669), including in Corsica since the French Revolution, was strengthened first during the 1920's [START_REF] Chalvet | La vulnérabilité de la forêt provençale face aux incendies : naissance d'une notion (fin XIXe siècle)[END_REF] and later during the 1980's [START_REF] Alexandrian | Les statistiques ''feux de forêt'' de ces trente dernières années[END_REF]. This latest fire suppression policy has probably contributed to the large fire of 2000 that was expected by increasing the time since last fire combined with a severe drought [START_REF] Piñol | Conditioning uncertainty in ecological models: Assessing the impact of fire management strategies[END_REF][START_REF] Evin | Has fire policy decreased the return period of the largest wildfire events in France? A Bayesian assessment based on extreme value theory[END_REF].

No change in fire season for 202 years

The majority of scars were formed in latewood and adjacent ring positions corresponding to summer and the first weeks of autumn [START_REF] Häusser | The dry and the wet case: Tree growth response in climatologically contrasting years on the Island of Corsica[END_REF], which is the driest period of the year for Mediterranean climate [START_REF] Ozturk | Projections of climate change in the Mediterranean Basin by using downscaled global climate model outputs[END_REF]. These results are similar to other studies [START_REF] Fulé | Forest structure and fire history in an old Pinus nigra forest, eastern Spain[END_REF][START_REF] Touchan | Fire history in European black pine (Pinus nigra Arn.) forests of the Valia Kalda, Pindus Mountains, Greece[END_REF]Christoupoulou et al., 2013;Sahan et al., 2022), which revealed that the majority of fire scars occurred mostly within latewood and during dormant season. Further, ring position of scars were similar through the whole studied period, indicating that the fire season was steady through fire years. Notably, this was also the season of the latest major fire in 2000 which happened on 27 th of August.

Fire management and conclusion

To sum-up, our 202 year-long history of wildfire regime in a black pine forest of central Corsica provides rational elements for improving forest management. Fire frequency changed twice since 1820, first around 1931 and then after 1970, and peaked significantly between 1931 and 1970 with short intervals. The fire season was steady, but most larger fires (7 out of 8) occurred before 1945. However, the largest and likely most severe ever recorded has occurred very recently in August 2000.

The forest was subject to frequent fires with ignition sources sometimes independent from drought; the relationships with human activities remain to explain, excepted the 1943 fire that is iconic of an anthropogenic event, the Second World War. Regarding the importance of fire frequency before 1970, and the highest number of major fires before 1945, human pressures could partly explain these changes in fire size and frequency. Indeed, forest uses decreased progressively throughout the 20 th c. However, Vizzavona is a key socio-economic crossroad in Corsica since centuries until today. Generally speaking, the land use is linked with ignition: the higher the land use, the higher the ignition risk [START_REF] Bowman | The human dimension of fire regimes on Earth[END_REF][START_REF] Moritz | Learning to coexist with wildfire[END_REF].

The synthetic mapping of fires (Figure 5b) suggests that topography and landforms probably control the fire spread at landscape scale in the black pine forest. A more fragmented landscape decreases the risk of severe fires. To define a management strategy, it is necessary to keep in mind that even though the main ignition source are land uses, drought episodes are currently more frequent and longer fostering more flammability. Rare ignition can result in large fires, like in 2000. Further, the increasing time since last fire (Figure 3a) increases the fire hazard (c parameter), and the landscape homogeneity favors the spread of wildfires.

The fire regime of the 19 th c. until 1930's that was about 80 years must be recover. It was characterized by low severity fires, probably surface fires, preventing fuel accumulation on the ground and improving seedbed for black pines by consuming litter and humus that contain abundant inhibiting components like polyphenols. By consuming fuel bed, such strategy should decrease the risk of large and severe fires. The hot and dry weather has only contributed to improve the fuel quality for burning. Sustainable forest management must consider low severity surface fire in the management of black pine forest, for instance based on prescribed burning.

In such case, medium-sized pines (i.e. neither mature overstory trees nor regeneration) should be thinned to break up the fuel ladder and, a fuel break should be established around the area to be burned. Larger trees should mostly be unaffected by surface fires due to their insulating characteristics, such as trunk diameter and bark thickness, as well as crown height, which protects the black pine from damage (Fréjaville et al., 2018b;[START_REF] Ferrat | Influence of prescribed burning on a Pinus nigra subsp. laricio forest: heat transfer and tree vitality[END_REF].

Figure 1 .

 1 Figure 1. (a) Map of Corsica displaying black pine distribution (green) according to the French

  Data were extracted from the INSEE (Institut national de la statistique et des études économiques) and EHESS (Ecole des Hautes Études en Sciences Sociales) databases that provided population census figures from 1800 to 2019 (Figure S5). Censuses of human populations were made every 5 years between 1831 and 2006 and each year since 2006. Before 1831, census intervals were not constant: 1800, 1806

  curve characterizing the flammability risk trend (McCarthy et al., 2001). A c value < 0 indicates a decrease of the flammability over time (t), c value > 0 indicates that the flammability (h) increases over time (t), while c = 0 indicates that the flammability is constant through time, such as: ℎ(𝑡) = ℎ𝑡 ! eqn. 1

Figure 2 .

 2 Figure 2. Facetted fire history chart per plot. Dashed horizontal lines indicate non-recording

  , ]1931-1970] and ]1970-2012]. Two of these periods: [1820-1931] (n = 5 intervals), ]1931-1970] (n = 7) were statistically different (Wilcoxon test, p = 0.015). The MFI for the period [1820-1931] was 22 ±14 years (Weibull median = 21 years, min = 12, max = 46 years), MFI for the period 1931-1970 was 6 ±4 years (Weibull median of 5 years, min interval = 2 years, max interval = 14 years). For the last period 1970-2012, FI values could not be calculated as it did not contain enough fire intervals (n = 2). The c parameter inferred from Weibull calculus indicates that it was 1.89 ±0.63 (unitless) for [1820-1931], and 1.48 ±0.42 for 1931-1970. Like the MFI for ]1970-2021], the c parameter could not be calculated. Over the whole period, [1820-2021], the c parameter was 1.18 ±0.24. Both c values for first and second period indicated that the flammability increased over time, but this increase was more important for the first period (1820-1931) characterized by longer FI (Table

Figure 3 .

 3 Figure 3. (a) Fire interval duration plotted against fire years. Red line is the local regression

Figure 4 .

 4 Figure 4. Fire seasonality summary showing the positions of scars in the tree-rings. EE: early

  and]1931-1970] periods. All fires between 1866 and 1931 burned at least 50% of the whole area, but after 1931, only three out of nine fires burned more than 50% of the sampled area. The difference is significant between (n = 5, 70 ±24% of the sampled area) and ]1931-1970] (n = 7, 31±22%) periods (Wilcoxon test, p = 0.03) but not between[1866-1931] and ]1931-2012[ (n = 9, 38 ±29%) periods (p = 0.07).

Figure 5 .

 5 Figure 5. (a) Spatial pattern of all 15 recorded fires. Black dots represent cross dated samples

Table 1 :

 1 Plot characteristics (mean values) of the study site (Vizzavona).

	Plot areas were

Table 2 :

 2 Number of samples (tree, stump, snag, log), total of cross-dated samples and time boundaries of chronologies

			Crossdated samples	Chronology (year AD)
	Plot Sample number (n)	(n)	(%)	Starting	Finishing
	1	8	7	88	1819	2021
	2	14	9	64	1855	2021
	3	10	8	80	1824	2021
	4	10	8	80	1796	2021
	5	11	9	82	1663	2021
	6	11	7	64	1631	2021

Table 3 .

 3 Fire return intervals (FI) per plot and for the whole study site (Vizzavona): total number of fire intervals, MFI, median FI and Weibull median, minimum and maximum values per plot and for the whole study area. The calculation of FI is bounded at 2012 (last fire date inventoried) because the period between 2012 and the sampling date (2021) is not a fire interval.

	Fire-return interval (FI, years)

"Major fires" refer to fire events scarring at least 25% of samples. Rule for brackets: ]1931-1970], means 1931 is not included in the period, and 1970 is included.

Acknowledgements

Authors are indebted to Fabrice Torre (DREAL-Corse) for his precious help, Amandine Burguet-Mortti (ENDEMYS), Olivier Riffard (Corsica administration), and also Sandra Guy, Antonella Massaiu and Germain Paolacci (ONF). Serena Felix (NAU) assisted with analysis of samples.

Funding

The study was carried out within the framework of the CorsicanFires program led by CC, and the International Emerging Action MedFires funded by the CNRS, Northern Arizona University, and EPHE-PSL, and co-led by CC and PZF (IEA00797). CorsicanFires was financially supported by the DREAL-Corsica (DREAL 2020-008), the national program CIFRE (ANRT-2021-0058) and ENDEMYS Ltd, which granted JB for his PhD. PZF received support from the Charles O. and Mary Minor Professorship at NAU.

Authors' contributions

Declaration of Competing Interest

The authors declare that none of them has an interest financial or personal which may be perceived as competing interest.


Audrey Lavallee

Marie-Charlotte Gandolphe

Xavier Saloppé

Thierry H Pham

Jean-Louis Nandrino

Characterization of Self-defining memories in antisocial personality disorder

DISCUSSION

An impairment in the retrieval of specific single event and to make a selection in their SDMs has been observed in participants with APSD. They have also difficulties to take lesson about their past.

We argued that their inabilities to recall specific single event and to integrate their SDM could impair their narrative identity. The narrative identity is fundamental to the have a continuity in the life-story and to imagined coherent future life goals [START_REF] Mcadams | Narrative identity[END_REF]. The integration impairment observed with person with ASPD is consistent with literature about persons with traumatic dissociation and could be associated with a lower level of mental health and well-being. Thus we argued that the clinical interventions with people with APSD should give careful consideration to the integration of their significant life events

*

  Contact : audrey.lavallee@univ-lille.fr A.Lavallee 1,2*; M.G. Gandolphe 1; X. Saloppé 1,3,4; T. Pham 2,3 & J.L. Nandrino 1 Characterization of self-defining memories in antisocial personality disorder of Lille, SCALab UMR CNRS 9193 (France); 2: UMons (Belgium); 3: Research center in social defense of Tournai (Belgium); 4: Psychiatric hospital of Saint Amand les eaux (France) METHOD Participants 22 inpatients in forensic hospital with ASPD and 22 healthy control men Procedure Participants were asked to retrieved 5 SDMs. The SDMs were characterized a posteriori by three independent investigators. Specificity A specific SDM = brief event with unique occurrence Kappa coefficient = 0.66 Type 1 = pure specific event Type 2 = specific event with generalization Type 3 = multiple single event Kappa coefficient = 0.71 Singer & Blagov (2000,2001) Integration An integrated SDM = SDM containing meaning making Kappa coefficient = 0.63 Singer & Blagov (2000,2001) Valence Positive, Negative, Neutral, Mixed Based on the use of emotional words in the telling Kappa coefficient = 0.74 INTRODUCTION Self-defining memories (SDMs) are highly significant autobiographical memories which has been described as particularly relevant in pursuit of personal goals. SDMs are distinguished from other autobiographical memories because they are specifically associated with the sense of personal identity and continuity in one's individual history. Several studies have identified modification in SDM construction in different pathological populations such as people with depression or posttraumatic syndrome. According to the numerous aversive events experienced by individuals with antisocial personality disorder (ASPD), and because of their difficulties to integrate their past events, the present study investigated the characterization of SDMs in individuals with ASPD. The aim was to understand how persons with ASPD used and recalled significant events of their past.

[START_REF] Nandrino | Characterization of Self-Defining Memories in Individuals with Severe Alcohol Use Disorders After Mid-Term Abstinence: The Impact of the Emotional Valence of Memories[END_REF] Percentage of SDM according to the type of specific SDMs of the ASPD and the Healthy-control samples


Scénographie hybride autour d'Evryali de Xenakis

Pavlos Antoniadis, Aurélien Duval, Jean-François Jégo L'impulsion initiale pour cette recherche-création a été le désir de renouveler un esprit distinctement xenakien, qui mélange les formes géométriques et l'expérience brute du vivant dans de nouvelles formes d'articulations. Comment pourrait-on augmenter l'expérience live de la musique absolue de Xenakis, en visualisant les énergies de la performance en temps réel qui

  d'ordinaire restent "en coulisses" ? Comment rendre accessibles au public les espaces symboliques du compositeur: ses modèles mathématiques, ses esquisses graphiques et ses partitions musicales ? Comment pourrait-on capitaliser sur l'intérêt de Xenakis lui-même, en tant qu'architecte, pour l'espace physique en tant que champ audiovisuel et créer de nouvelles conditions d'habiter ses créations ? Nous abordons ces problématiques par la création d'un espace virtuel, augmenté et interactif, qui croise partition musicale, mouvement du pianiste et espace physique. Le spectateur est immergé dans cet espace composé de projections spatialisées sur scène pendant la performance live. Les outils performatifs pour la visualisation des données multimodales de l'interprétation pianistique ont été développés par Aurélien Duval, dans le cadre du projet du pianiste et musicologue Pavlos Antoniadis soutenu par l'EUR-ArTeC, en collaboration avec les chercheurs de l'Université Paris 8 Makis Solomos (MUSIDANSE) et Jean-François Jégo (INREV-AIAC), ainsi que Frédéric Bevilacqua (ISMM, IRCAM).Evryali, une création de 1973 pour piano seul, signifie « un autre nom de la Méduse, qui veut dire 'mer étendue'. Cette pièce contient la naissance des "arborescences" qui seront exploitées par la suite plus amplement. L'arborescence est un enchevêtrement de lignes dans l'espace hauteurstemps. Cet enchevêtrement tels un buisson, une arborescence, subit des rotations, des dilations, des déformations, etc. » (Iannis Xenakis). La partition est composée à partir de ces arborescences esquissées sur papier millimétré. Cette expansion orgiastique d'une polyphonie innovante, qui évoque l'infini insaisissable de la mer ou l'énergie incontrôlable des vagues, pose un défi pour les interprètes. Ceux-ci se trouvent constamment dans la position de ne pouvoir physiquement agripper les textures musicales en maintenant le tempo indiqué par Xenakis. De plus, il est presque impossible d'entendre les nuances harmoniques infinitésimales des accords étendus. Très souvent, les pianistes font le choix de simplifier ces textures par omission des notes ou branches de la polyphonie, une stratégie que nous avons décidé de ne pas suivre. Par contre, l'exécution de toutes les notes a été notre contrainte principale. Cela nous a poussés à développer des techniques de 'piano stride' et des accords brisés en plusieurs directions, afin de faire sonner les textures complexes dans un tempo flottant, qui dépend de la densité des textures. Afin de saisir la performance du pianiste, nous avons utilisé la technique de capture de mouvement au moyen d'une combinaison composée de capteurs inertiels. Les gestes sont enregistrés et reproduits en temps réel sous forme de données numériques visualisables sur un double virtuel du performeur. La scénographie créée est inspirée des polytopes de Xenakis : installations participatives mises en espaces et composées d'éléments physiques et vivants. Elles permettent d'explorer de nouvelles façons d'habiter les créations. Des interfaces de régie modulaires ont été développées afin de contrôler les différents effets scéniques dont une partie est accessible de façon participative : un spectateur peut venir manipuler les commandes en collaboration avec un régisseur-performeur. Une grande projection au fond de la scène permet d'afficher de façon interactive le double virtuel du pianiste à la première ou la troisième personne. Des éléments graphiques représentent les vecteurs d'accélération et de vitesse des deux mains. Les esquisses de Xenakis ont été retravaillées et séparées en fonction des différentes parties du morceau et sont visibles au centre de la projection. Dans l'objectif de dépeindre l'espace sous-marin dans lequel Evryali s'inscrit, des effets de reflets d'eau appelés caustiques sont projetés dans le public et au plafond. Les spectateurs se retrouvent immergés dans cet environnement virtuel modulé en temps réel qui donne à voir des éléments d'ordinaire invisibles. Le choix délibéré de montrer l'artifice technologique fait partie intégrante de l'interprétation : la phase d'équipement de la combinaison, habituellement cachée, est orchestrée à la manière d'un rituel. La régie n'est pas en retrait non plus, mais sur le côté de la scène, mettant en avant les différents acteurs de la performance, qu'il soit régisseur ou spectateur invité à interagir. Les multiples projections spatialisées sur la scène, le plafond et le public créent un volume d'habitation sensorielle. La visualisation des mouvements du pianiste permet de dilater les micro mouvements du corps d'ordinaire invisibles à l'oeil nu, notamment des mains. Les spectateurs assistent de cette façon à une version de la performance augmentée par des éléments kinesthésiques qui participent à rendre l'expérience du concert synesthésique. En conclusion, ce concert augmenté invite à habiter un monde polysensoriel rendant poreuses les frontières entre la scène et le public, l'interprète et son avatar numérique, le régisseur et le performeur, les espaces physiques et symboliques. L'espace immersif, en écho au volume de la mer large comme espace de rencontre et d'hybridation, propose une nouvelle forme d'accès aux éléments savants de Xenakis.

Addendum

Les auteurs remercient Mâkhi Xenakis et Makis Solomos pour l'accès aux esquisses. Ce travail a bénéficié d'une aide de l'EUR-ArTeC, ANR-17-EURE-0008. Lien video de la performance : https://youtu.be/whmWSoxOBEs