Barnabé Faliu

PARTICIPATORY DESIGN, CREATIVITY, CO-DESIGN, 3D MODELING, 3D COLLAGE Urban Design

SHAPING THE PACE -A DIGITAL DESIGN HEURISTICS TOOL TO SUPPORT CREATION OF URBAN DESIGN BY NON-PROFESSIONNALS

Introduction

Citizen participation in urban projects has imposed in the last decades as one of the key for success. It is clearly identified there is a lack of communication and collaboration between citizens and urban design experts which can lead to conflictual situations. The stakes of these projects are generally too critical to leave citizens voices apart. Urban designers and local authorities should not forget end users when designing public places in order to respect their quality of life and their 'ownership', in the sense of (De Lange and De Waal 2013), whom define it as "the right to act upon an issue…, a sense of belonging to a collective place". Moreover, regarding the nation legal framework of France (Article L103-2), participatory processes are mandatory for urban projects aiming to modify the living environment of citizens. As a result, a huge number of methodologies and toolkits have been developed lately, applicable to different steps of urban projects whether it is urban planning or urban design. Among these methodologies, an increasing number is focused on ICTmediated citizen participation in urban issues which are "technology being addressed in such areas as governance, urban planning, information systems and interaction design, geography, citizen activism and community development" (Saad-Sulonen and Horelli 2010). The ambition of ICT tools is to provide a digital interface between urban design experts and citizens to let them collaborate and benefit from each other's knowledge.

In the first section, we present a non-exhaustive state of the art of interactive and immersive tools for participatory design. We are mainly focusing on ICT tools. Second, we introduce a case-study held in the city of Marseille by Euroméditerranée, from which we have some first observations to share. The first two sections permit us in a third section to define a 3D modeling tool included in a scenario to involve citizens in urban design projects. Finally, we present first results of implementation of the tool and future work planned.

Interactive and Immersive tools for Participatory Urban Design

Urban design is a multidisciplinary process to create places for people and define their interactions with it. The work done is mainly related to public places like plazas, parks, open spaces or streets. Urban designers have to consider the needs, habits and customs of the different kinds of citizens that will use the place and imagine how they will experience it. In the other hand, economical, technical, political and sociological constraints must be considered during a short-range period of approximately five years, to come to a successful solution adapted to needs of everyone. Urban design is a complex process due to the important number of stakeholders, representing different interests: local residents, local authorities, associations, special interest groups, urban planners, urban designers, architects and more. More generally, we can simplify it in two distinct groups, professionals and endusers. Professionals represent urbanism experts and decision makers. End-users represent the people that will live with the newly designed place. On top of it, other issues as ecological challenges, social equity, culture, safety or water supply influence both the choices made by professionals, and the debate or needs risen by end-users.

To tackle the complex situation of urban design, many people worked on solutions to enhance stakeholder's collaboration. (Sanoff 2000) divided participation methodologies in urban planning and design into six main categories:  Awareness methods: Inform people about the ongoing project and the main issues through exhibits, medias or walking tours.  Group interaction methods: Better known as workshops, whether it is a focus group of meticulously selected people or an open session, it aims to solve a particular problem through series of working sessions mixing professionals and end-users.  Gaming methods: Gaming methodologies places participants into a real-life context in order to solve an identified problem. The context is composed of participants, rules, constraints and methodologies. It can act as an educative process for citizens (and professionals), or as a way to solve issues between multiple stakeholders.  Indirect methods: Questionnaires and interviews to grasp citizen's opinions and needs;  Open-ended methods: Methodologies where participants have the less constraints to express themselves.  Brainstorming methods [START_REF] Salter | The Digital Workshop: Exploring the Use of Interactive and Immersive Visualisation Tools in Participatory Planning[END_REF]), (Saad-Sulonen and Horelli 2010) and (van Heeswijk 2017) demonstrate in case-studies that the usage of interactive and immersive tools in participatory planning is greatly approved by citizen. It helps to better understand the environment and issues for non-professionals but it also helps with connecting urban planning, community development and local governance. Interactive and immersive tools for participatory urban design can be defined as a group interaction method as well as a gaming method since from one side it connects experts and citizens whom can share experience and knowledge, and from another side it is a constrained environment with rules aiming to solve an identified problem. The gamification also enables an educative process regarding the local community. Digital tools are also a great support for co-creation and permit bottom-up (local) initiatives supervised by top-down (institutions) rules to end with comprehensive and high-quality design propositions.

The following list presents a few existing interactive and immersive tools for participatory urban design: Case Study: Euroméditerranée in Marseille, the Bougainville Park

Context

Euroméditerranée is a consequential project held in Marseille, France, focusing on urban planning and economic development since 1995. It has been initiated by French government, the city of Marseille, the region Provence-Alpes-Côte d'Azur and is financed by Europe. Euroméditerranée is the contracting authority responsible for urban planning, project management and funding of the different urban projects included in a 480 hectares area. Currently in the second phase of the global project, Euroméditerranée started working on the construction of an urban park, so called Bougainville Park, which is a 4 hectares terrain at a central position of the city: it is surrounded by a metro station, residential districts, joint ownership properties, an elementary school and a social housing building. It aims to be the "green lung" of the district which is more or less an industrial wasteland for the moment. The main desire of the team is to offer a high level of involvement of the different stakeholders and more particularly the citizens and local associations representing residents in order to get a consensus of opinion, and consequently a successful and cost-effective project that is representative of the local needs. The next section will present the participatory methodology used by Euroméditerranée to involve citizens in urban design.

The project started in Mars 2016 with a clear view of the methodological approach, that is oriented on co-designing the park with workshop's participants and local residents, three years before the construction work starts. From this point, inputs data where already identified such as: a budget, existing infrastructures, a soil survey, flooding risks, pollution, topological information and social context. Two major objectives have been defined:

 The definition of temporary infrastructures in order to provide quickly some elements of the future park.  The definition of a pre-planning in dialogue with participants and local residents, which will act as a recommendation list for the prime contract, a landscape specialist company. The objective is to define the features and uses of the park.

On this basis, Euroméditerranée proposed three phases before the start of construction:

 Pre-consultation: Workshops -Choices of the temporary infrastructure and first draft of a pre-planning intended for landscape specialists.  Selection of the landscape specialist: 5 teams were in competition to gain the project. The citizens were not involved in the selection process, nevertheless, one of the mandatory requirements to win the competition was the acceptance co-design methodology.  Consultation: Workshops in collaboration with the selected landscape specialists for three consecutive phases of urban design (sketch phase, pre-project phase, project phase).

Workshops

The co-design workshops organized by Euroméditerranée were inspired by the Participatory Prototyping Cycle framework [START_REF] Sanders | Prototyping for the Design Spaces of the Future[END_REF]). Different stakeholders, professionals or non-professionals, were melted to make and tell on key subjects like security, local culture, history of the district, and finally co-creation of design propositions. Enacting is not part of the current process. During co-creation sessions, several questions have been answered either with the usage of make tools, or through a simple vote. For instance, in order to gather the needs about the open question: 'What features should appear inside the park and where?', participants were working in groups of 5. They were given a 2D map centered on the future area of the park. The animators of the workshop (Euroméditerranée) also gave printed images of the most common features to each group (skate parks, public facilities, playgrounds, trees, …) along with scotch tape and scissors. Then each group had to stick the images on the map, at the position they want it to be. This process of course lead to debates inside each group. At the end of the session, a group by group presentation is made and the animator realizes a synthesis to identify the key needs of the citizens throughout the propositions. After each workshop, outputs are delivered to local authorities so they can identify early the main issues of the project.

Workshops observation

We participated to almost every workshop, hence we had the opportunity to analyze the benefits and limitations. The methodology used by Euroméditerranée confirm the theory that participatory urban design is helping with the acceptance, the ownership, of the project by citizens. The general feeling is positive and the multiple workshops created quality debates and propositions. This will permit professional to work in line with the needs of the inhabitants.

Nevertheless, the audience wasn't fully representative of every kind of inhabitant of the district, which is problematic because their needs aren't heard. Moreover, a huge turnover has been noticed between each workshop, except for a core group of approximately five persons. The overall feelings of the citizens about the participative methodology was mixed, some participants had their trust in the project enhanced, and others were frustrated because it was too long, or because of some political announcements made late that created a feeling of treason. Regarding the co-creation process, we identified some drawbacks that will lead us to the definition of a numeric tool to support participatory urban design:

 Participants have a wrong understanding of spaces and relief,  Printed images are not convenient when looking for a particular feature/atmosphere, Understanding of technical, political and financial constraints could be enhanced,  Collaboration can be enhanced between professionals and non-professionals

Definition of a 3D Modeling tool to engage citizens and enhance their creativity

To answer the drawbacks listed previously, we propose an interactive and immersive digital tool to help citizens' understanding, enhance their creativity and their knowledge of urban design constraints. Based on [START_REF] Salter | The Digital Workshop: Exploring the Use of Interactive and Immersive Visualisation Tools in Participatory Planning[END_REF]), (Saad-Sulonen and Horelli 2010) and (van Heeswijk 2017) observations concerning the usage of digital tools in urban design, we choose to create a 3D modeling tool in order to support spaces and relief understanding. Alike the participants of Euroméditerranée's workshops, the users of the tool have access to a large digital database of categorized 3D models, meaningful for urban design. Inside the database, one should be able to find models from a complex playground to a basic shape and manipulate it easily: select, move, rotate, scale, deform and delete. Some characteristics of the model could also be changed as the color or the material.

To support creativity, we propose a 3D collage metaphor to support the divergence phase of creation. A user should be able to start from an existing model and create a new one by cutting it, merging it with another model and resize it. Hence, we add 3D cutting and merging metaphors to our tool palette.

Such a tool should provide a friendly user interface for non-professional, as well as background processes producing statistics of usage for professionals and help them in decision making. To support collaboration, we propose the use of an interactive table upon which multiple participants could interact with natural gestures instead of being alone in front of a computer using a keyboard and a mouse.

To enhance spaces and relief understanding, we propose to implement an immersed visualization mode, in a 1-1 scale, thanks to a virtual reality headset. Thus, participants would be able to walk through their design proposition and fully experience the place. For instance, they could realize that a building isn't well positioned because it is hiding a nice sea-view. We can also introduce an audio feature to improve the understanding of the impact of a building regarding an existing noise source, a street with heavy traffic for example. A collaborative aspect is present here as well through the possibility to annotate the proposition and leave audio comments, or emoticons representing a feeling.

Finally, to improve citizen's understanding and bring an educative characteristic to the tool, we want the use semantically enriched 3D models, in the manner of (Panagopoulos, Andrade, and Barreira 2009). They made research to embed meaningful data in 3D models such as economic, legal or social data. This methodology is useful for both experts and amateurs. Of course, such a feature should let users enrich information themselves. For example, information relative to the noise approximately generated by a 3D model can help user to place things wisely, whether it is a highway or a swimming pool. Another interesting extra information would be a categorization of models and newly created (cut and paste) models. By categorization we mean giving an explicit functionality to each model, like 'this is a basketball terrain' or 'this is a bench'. This feature will help professional in decision making thanks to data aggregation. For instance, if every object of the urban design proposal is well categorized, analytics can be made to evaluate, among every proposal, the percentage of citizens interested in a football terrain and where they want it to be. Another example of semantically enriched 3D models is the definition of constraints inside the workspace: we want an admin user to be able to define places where no objects can be dropped by drawing, as it is illustrated in (figure 1). The user can only place objects inside the red grid-pattern. The goal is the creation quality urban propositions by limiting users' possibilities.

To summarize, we define two different workspaces, leading to an iterative process of work-visualize-rework:

Scenario of usage

The tool is intended for urban design projects accepting participatory design concepts. During the sessions, multiple stakeholders can be involved, this is why we have to define clear roles and responsibilities regarding the usage of the tool. We identified four different roles: the contracting authorities, the project supervisors, the animators; called the professionals; and the citizens. Their responsibilities are detailed in (figure 2). Just like Euroméditerranée's methodology, the tool shall be used along multiple workshops carried out a long while before the start of construction work. The following is a proposition of hypothetical steps that illustrates the usage of the tool for an urban park:

 Step 1: An initial brief is made between professional.

First results of implementation

Implementation effort has already been made regarding the tool. We are using the cross-platform game engine Unity to create an interface that will suit for both interactive table and VR Headset. We implemented a draft version of the interface (figure 3) which permit to navigate in the virtual world, zoom, rotate and tilt the camera. We also imported a 3D City model (.obj file) generated from OpenStreetMap data (.osm file) with the use the open-source third party software OSM2World (http://osm2world.org/). We also implemented an interface to drag and drop 3D objects from a carrousel menu accessible in the virtual world. First test with immersive view has already been made with a Google CardBoard, using Google's VR SDK for Unity. It clearly appears that mobile phones are not powerful enough in terms of graphic rendering to provide a fluid and pleasant experience to users: the video is not fluid gazing around, which can lead to motion sickness. Finally, we worked on a virtual mesh cutting algorithm, necessary to implement the 3D collage metaphor. We are relying on an open-source library called CGAL (http://www.cgal.org/) written in C++, which is communicating with Unity as an external plugin. CGAL permit us to manipulate 3D models as triangulated meshes and apply mathematical operation on it, and then send it back to Unity when the computation work is finished. We decided to implement the cutting metaphor as follow: a user draws a line on the desired element to cut, then a triangulated surface is generated from this drawing that intersects the shape with its current position. Finally, the cut is computed by looking for the intersection points between the target model and the surface. Then two different models are sent back to Unity.

Future work and conclusion

This paper presented the definition of a 3D Modeling tool to engage citizens in urban design projects and foster collaboration between experts and amateurs. The tool has been defined on the basis of observations taken during Euroméditerranée's workshops, our casestudy. More observation opportunities will come in the next 2 years until the construction work starts. It will permit us to realize tests and refinements of our tool. To do so we intend to organize workshops mixing citizens and professional to challenge the functionalities we specified, but also to work with test groups on subjects such as the interaction metaphors of the interactive table. Specific workshops will be realized focusing either on experts' benefits or citizens'. Moreover, we intend to realize questionnaires to grasp users' feelings about the experience we propose. Finally, huge effort will be made on implementation to provide all the functionalities described in this paper and offer a collaborative, intuitive, interactive and educative experience in urban design.



  The creation workspace: Usage of an interactive table. It is composed of three data layers: o Map layer: Geometric data used to generate the workspace. o Semantic layer: On top of the previous layer a user can add constraints and useful information. o Creation layer: On top of the semantic layer, a user can manipulate and place 3D models and text comments.  The immersed visualization workspace: usage of a virtual reality headset to walkthrough the proposition realized in the creation workspace. Possibility to add comments.

Figure 1 :

 1 Figure 1: Data layers of the creation workspace



  Step 2: Pre-configuration of the tool between professional. Here, the initial map would be imported as well as the identified constraints/information. The database shall be filtered at this step if necessary, to avoid unrealistic proposition.  Step 3: Definition of additional constraints and rules thanks to local residents' knowledge and culture.  Step 4: Functionality definition workshop, what functionality should appear and where? People are divided in multiple groups and make 3D propositions with the interactive table.Each group can use the immersed visualization workspace the validate the proposition or refine it if necessary. At the end of the session, participants can use the tool to present, debate and choose the final proposition.  Step 5: Zoom-in workshop on each functionality to work on their shape in collaboration with project supervisors. Example themes: "The shape of the trash bins", "The shape of the fountains".

Figure 2 :

 2 Figure 2: User roles

Figure 3 :

 3 Figure 3: Draft user interface of the tool



  Interactor from (van Heeswijk 2017): A software assisting users in creating their own world in 3D for urban renewal, graphic art or design. It permits manipulation of 3D objects and textures. Objects can also be reworked through a 2D drawing mode where users can cut, paint or draw.  Terf (3D Immersive Collaboration 2014): A multi-user virtual world used for long-distance collaboration of multiple stakeholders in companies, and more particularly construction management. It offers several points of view (first person, bird view, …) to manipulate 3D models (from a database or imported) or 2D images. Additional features are available like voice and text chat, webcam video, placement of 360 audio sources and in-game usage of programs like excel or word. It is also linked with external programs as SketchUp or ArcGis.  The Betaville Project (Skelton 2013) offers a "massive participatory online environment for distributed 3D design and development of proposals for changes to the built environment".

Multiple actors can be connected to the same virtual city and 'fly through it', model new structures, leave comments and engage a real-time discussion.  (Westerberg and Von Heland 2015) promoted the use of the Mojang AB's video game Minecraft to build propositions in a virtual city using the Minecraft tools. Feedback tools such as commenting produced design proposals are also available.  City I/O ("Changing Places" 2017) proposes a table with an urban model on top build out of Lego pieces. One can see the representation of the urban model in 3D on a screen that is directly linked to the physical model with extra textures added like trees and building shapes. Two modes of interaction are possible: one by adding/removing Lego blocks on the table and seeing the change on the screen; or by interacting with the virtual model for softer actions like changing building colors or adding a comment. The virtual scene can be visualized either on a TV screen or on a mobile device using an AR application.

PhD Student, Yncréa Méditerranée, ENSAM Le2I, Toulon, France, barnabe.faliu@yncrea.fr


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J L Dussossoy

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C Gervais

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D R Neuville

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C Fillet

Structural Characterizations of Rare Earth-Rich Glasses for Nuclear Waste Immobilization

New nuclear glass compositions, able to immobilize highly active liquid wastes arising from high burn-up UO 2 fuel reprocessing, are being studied. Investigations are being performed on rare earthrich glasses, known as durable matrices. After a preliminary study, a basic glass composition was selected (Glass A, wt. %) : 51.0 SiO 2 -8.5 B 2 O 3 -12.2 Na 2 O -4.3 Al 2 O 3 -4.8 CaO -3.2 ZrO 2 -16.0 Nd 2 O 3 .

The aim of this study is to determine the local environment of the rare earth in this glass and its evolution according to neodymium. To achieve this objective, glasses were prepared from the baseline Glass A with variable neodymium oxide amounts (from 0 to 30 wt. % Nd 2 O 3 ). By coupling characterization methods such as EXAFS (Extended X-Ray Absorption Fine Structure) spectroscopy at the neodymium L III -edge, optical absorption spectroscopy, 11 B, 27 Al MAS-NMR and Raman spectroscopy, pieces of information on the rare earth surroundings in the glass were obtained.

INTRODUCTION

New nuclear fuels with high discharge burn-up (60 000 MWj/t) have been studied for some years in France. Reprocessing of this nuclear spent fuel will generate HLW more concentrated in fission products and minor actinides than nowadays. Therefore, new glass compositions have to be developed, able to immobilise these wastes as a whole. These matrices must exhibit excellent chemical durability and higher glass transformation temperature (T g ) than those of the current borosilicate nuclear glasses. As the actinides and lanthanides quantity is expected to be higher in the new spent fuel, our research turned towards rare earth-rich glassy matrices. Nevertheless, lanthanide aluminoborosilicate glasses (LaBS) or lanthanide aluminosilicate glasses were not chosen in this work because of their high melting temperature (T m ≥ 1450°C) [1,2]. Indeed, process problems could arise from the volatility of some fission products during melting and from the limited resistance of stainless steel containers during melt casting at such high temperature. After a preliminary research, an alternative glass composition was selected for this study (Glass A, wt. %) : 51.0 SiO 2 -8.5 B 2 O 3 -12.2 Na 2 O -4.3 Al 2 O 3 -4.8 CaO -3.2 ZrO 2 -16.0 Nd 2 O 3 . In this simplified system, more than 75 wt. % of the new HLW are simulated (the other 25 wt. % did not play a fundamental role in the properties of the glass and were thus eliminated for this structural study). Relatively large quantities of sodium and boron oxides were introduced (known as fluxing agents) so as to decrease the melting temperature below 1300°C. In the following work, both environment around the rare earth in Glass A and its evolution according to Nd concentration were studied. To this end, techniques such as EXAFS spectroscopy at the L III -edge of neodymium, optical absorption spectroscopy, 11 B, 27 Al MAS-NMR and Raman spectroscopy were used.

EXPERIMENTAL

From Glass A, nine samples were prepared, containing 0, 1.3, 2.5, 5, 10, 16 (= Glass A), 20, 25 and 30 wt. % Nd 2 O 3 . Two glasses were also prepared with lanthanum (16 and 30 wt. % La 2 O 3 ) for MAS-NMR studies. Glasses were produced after thorough mixing of reagent grade oxide (SiO 2 , H 3 BO 3 , Al 2 O 3 , ZrO 2 , Nd 2 O 3 ) and carbonate (Na 2 CO 3 , CaCO 3 ) powders. All glasses were melted at T m = 1300°C for 3 h in a platinum crucible (excepted for Nd25 and Nd30, with a T m of 1400°C because of crystallisation problems). EXAFS analyses were performed at the LURE-DCI synchrotron source (Orsay, France), using the Nd L III edge (6.2 keV). All X-ray absorption spectra were recorded in transmission mode. Data were collected under vacuum at 77 K (liquid nitrogen). EXAFS spectra were extracted with the software developed by A. Michalowicz (EXAFS_98. ppc) [START_REF] Michalowicz | EXAFS pour le MAC[END_REF][START_REF] Michalowicz | [END_REF] and data analysis was performed with FEFF-Fit [5], following standard methods based on scattering theory. Simulations of the first and second nearest neighbors were realized by using the theoretical backscattering phase and amplitude functions calculated with the ab-initio code FEFF 8.0 [5]. Nd 2 O 3 , Nd 2 Si 2 O 7 and Ca 2 Nd 8 (SiO 4 ) 6 O 2 crystalline phases were used as model compounds. Due to the large static disorder occurring around neodymium in our glasses, a cumulant analysis [6][7] of the first shell (Nd-O) was preferred. In this case, ρ(R), the radial probability distribution of atoms in the shell, is expressed as a power series of cumulants C i (1):

∑ ∫ ∞ = ∞ - = 0 0 2 2 ) ( 2 ! ) 2 ( ) ( ln n n n kR i k R C n k i dR e R e R λ ρ (1)
Third and fourth cumulants (C 3 and C 4 ) are thus necessary to characterise the large asymmetric distribution of distance. The third cumulant describes the asymmetry of the distribution whereas the fourth cumulant depicts symmetry deviation from Gaussian shape [6][7]. Optical transmission experiments were carried out at low temperature (T ≈ 10 K) on polished glass samples (thickness from 0.5 to 1 mm). Raman measurements were carried out on a T64000 Jobin-Yvon confocal microRaman spectrometer equipped with a CCD detector. The 514.532 nm line of a Coherent 70 Ar+ laser was used for sample excitation. This line operated between 2 W and 0.5 W. MAS NMR spectra were recorded on a Bruker Avance 400 spectrometer at a frequency of 128.28 MHz using a Doty probe with no probe background for 11 B and on a Bruker DRX600 liquid spectrometer (14.1 T) operating at 156.38 MHz and equipped with a Bruker high speed MAS probe-head for 27 Al. Chemical shifts were either determined relative to liquid BF 3 OEt 2 (δ = 0 ppm) or to an acidic aqueous solution of Al(NO 3 ) 3 (1M). The spectra were simulated with the DMFIT program [8] which has been developed specifically for solid state NMR experiments, including simulation of quadrupolar shapes [9].

RESULTS AND DISCUSSION

EXAFS at the L III -Nd Edge Spectroscopy

Five glasses were analyzed by EXAFS : Nd2.5, Nd5, Nd10, Nd16 (= Glass A) and Nd30. Fourier transforms of the EXAFS signals (Fig. 1) display a steady decrease of intensity with increasing neodymium amount in glass. According to the fits results (Table I), neodymium always appears surrounded by 8 ± 1 oxygen atoms at a mean distance of 2.46 ± 0.03 Å. Moreover, approximately 3.5 silicon or sodium take place around neodymium ions at about 3.98 ± 0.03 Å. Nevertheless, although boron is not distinguishable by EXAFS, it is very probable, according to the Bray's model [10] for the SiO 2 -B 2 O 3 -Na 2 O system, to find boron in the vicinity of neodymium in our glasses. EXAFS, even for high neodymium contents. In our glasses, only a significant increase of the static disorder in glass is observed with increasing neodymium concentration (represented by σ 2 (Debye-Waller factor), C 3 and C 4 cumulants), responsible for the decrease of intensity observed on the Fourier transforms.

Optical Absorption Spectroscopy

Optical transmission measurements were performed at T ≈ 10 K. At this temperature, only the first of the five Stark levels of the 4 I 9/2 ground state of neodymium is populated. Among all the electronic transitions of Nd 3+ ion, two ones are of particular importance for the present investigation. Firstly, the transition between the In our glasses, peaks profiles (inhomogeneous half-width and position in energy) of the 4 I 9/2 → 2 P 1/2 transition of Nd 3+ (Fig. 2 (a)) do not display any evolution with neodymium concentration in glass. Peaks maxima are all centred at 23 226 cm -1 and bands shapes were fitted with one Gaussian getting a constant half-width of 120 cm -1 . According to these results, it can be put forward that the (Nd-O) bonding and also the nature of the Nd-surroundings must not show strong evolutions with neodymium content. However, the hypersensitive 4 I 9/2 → 2 G 7/2 , 4 G 5/2 transition (h.s.t.) shape (centred at 17 120 cm -1 and 17 460 cm -1 ) presents slight evolutions with neodymium concentration (Fig. 2 (b)). Indeed, shoulders present at the lowest energy side, strongly emphasized at low neodymium concentrations, become progressively less apparent as [Nd 2 O 3 ] increases, simultaneously occurring with a band broadening. This can either be due to an increase of the Nd-sites distribution and also an increase of the static disorder as neodymium content increases in glass (also shown by EXAFS), or due to an increase of the mean field strength Z/a 2 (Z is the cation valence and a the sum of the cation and oxygen radius, field strength is composed by Na + , Ca 2+ and Nd 3+ contributions). Indeed, according to Dymnikov et al [11], with increasing Z/a 2 , the h.s.t. become less resolved and shoulders disappear (for both silicate and borate glasses).

B and 27 Al MAS-NMR

MAS-NMR studies were realized on glasses prepared with lanthanum instead of neodymium. Indeed, using Nd 3+ (paramagnetic ion) involves broadened NMR signal shapes due to the dipolar interaction between its electronic spin and the nuclear spin of the studied nuclei.

B MAS-NMR

Earlier 11 B MAS-NMR studies realized on borosilicate minerals and glasses [12][13][14][15] have shown that tetrahedral BO 4 and trigonal BO 3 sites exhibit distinct chemical ranges. By integration of the area of these two signals, relative intensities of the two types of sites can be determined (Table II). In these glasses, the BO 3 units proportion, at a fixed BO 4 one, strongly increases as neodymium concentration increases (Fig. 3).

Raman Spectroscopy

Raman spectroscopy of oxide glasses is interesting especially in the high-frequency envelope [800 -1250 cm -1 ], in which T-O stretch frequencies (with T = Si, Al) occur. As increasing neodymium content in glass, a shift of the SiO 4 Q n units to the lower frequencies is observed (Fig. 4). According to previous investigations [START_REF] Li | [END_REF][20], this shift could probably be due to the creation of Q 3 (Nd) and Q 2 (Nd) units, arising at lower frequencies than the corresponding Q 3 (Na) and Q 2 (Na).

CONCLUSIONS

In all Ndx glasses, neodymium appears surrounded by 8 oxygen atoms and ~ 3.5 second neighbors Si / Na / B, with no significant evolutions in the Nd-neighbouring. Only an increase in the Nd-sites distribution is observed along with neodymium content. No Ndclustering occurs at less than 4 Å. According to all these results, it appears that neodymium probably imposes its environment to the glass.

Fig. 1 .

 1 Fig. 1. Fourier transforms of Nd L III -edge EXAFS spectra of glasses containing 2.5, 5, 10, 16 and 30 wt. % Nd 2 O 3 (T=77 K).

4 I 9 4 G 5 /

 4945 /2 ground state and the 2 P 1/2 excited state (around 23 225 cm -1 , Fig.2 (a)) brings information on the variety of sites occupied by Nd 3+ ions in the glass and on the degree of covalency of the bonding (Nd-O). Secondly, the transition between the 4 I 9/2 state and the 2 G 7/2 , 2 states (around 17 300 cm -1 , Fig.2 (b)), called hypersensitive, owns shapes strongly affected by changes in the environment around Nd 3+ ion.

Fig. 2 .

 2 Fig. 2. 4 I 9/2 → 2 P 1/2 (a) and 4 I 9/2 → 2 G 7/2 , 4 G 5/2 (b) transitions of Nd 3+ for Ndx glasses at T ≈ 10 K (1.3, 5, 10, 16 and 30 wt. % Nd 2 O 3 ). * indicates shoulders on the band. (The intensities of the peak maxima were normalised to the same arbitrary value).

Fig. 3 .

 3 Fig. 3. 11 B MAS-NMR signals of glasses containing 0, 16 and 30 wt. % of RE 2 O 3 . Intensities were normalised to the same arbitrary intensity of the BO 4 shape.

Fig. 4 .

 4 Fig. 4. Raman spectra of Ndx glasses.

TABLE I .

 I Quantitative results of the EXAFS analysis of the Ndx glasses with N i , the number of neighbours, σ i , the Debye-Waller factor and R i , the distance (Nd-neighbours).

			Sample number
			Nd2.5 Nd5	Nd10 Nd16 Nd30
	Νd-Ο	N R (Å) σ 2 (Å 2 ) 0.020 0.022 0.020 0.021 0.021 8.1 8.5 7.7 8.0 7.8 2.44 2.45 2.47 2.46 2.48
	C3 (Å 3 ) *10 -4	12	14	16	13	17
	C4 (Å 4 ) *10 -5	41	40	28	29	29
	Nd-Si/Na	N R (Å) σ 2 (Å 2 ) 0.011 0.013 0.014 0.013 0.014 3.5 3.5 3.5 3.5 3.5 3.98 3.98 3.99 3.98 3.99
	Global quality of fit of 99.7 %
	Otherwise, fit tests performed for all glasses with
	neodymium ions as second neighbours display
	aberrant fit parameters values (Debye-Waller factor σ > 0.30 Å and quality of fit < 65 %). That
	means that no phenomena of Nd-Nd clustering at
	less than 4 Å were detected in these glasses by

  11 B MAS-NMR signals of glasses containing 0, 16 and 30 wt. % of RE 2 O 3 . Intensities were normalised to the same arbitrary intensity of the BO 4 shape.

		0.64
		0.6
	A b so rb a n ce (re l. u nits)	0.4 0.44 0.48 0.52 0.56		Nd30 Nd16 Nd10
				Nd5
		0.36		Nd1,3
		0.32
		2.29 10 4	2.3 10 4	2.31 10 4 2.32 10 4 2.33 10 4 2.34 10 4 2.35 10 4 wave number (cm -1 )

TABLE II .

 II Proportion of BO 3 and BO 4 units in glasses containing 0, 16 and 30 wt. % of RE 2 O 3 IV) units) in all glasses. In oxide glasses, aluminium ions thus form [AlO 4 ] - entities[START_REF] Engelhardt | High resolution solid-state NMR in silicates and zeolites[END_REF][START_REF] Smith | [END_REF][START_REF] Stebbins | Handbook of physical constants[END_REF].

	(RE = Rare Earth)
	Sample number % BO 3 units % BO 4 units
	RE 0	42	58
	RE 16	62	38
	RE 30	80	20
	27 Al MAS-NMR
	27 Al MAS-NMR study allows to determine the
	different coordination states of the Al 3+ ions in
	glasses (Al(IV) around 60 ppm, Al(V) between
	25 and 40 ppm or Al(VI) between -15 and 20
	ppm). In Ndx glasses, chemical shifts and band
	shapes do not display any evolution with
	neodymium content in the glass. At a constant
	chemical shift of ~ 57 ppm, aluminium ions
	seem only to be present in four coordination
	number (Al(


Cl Emence Guiller
email: clemence.guiller@imbe.fr

Laurence Affre

Magali Deschamps-Cottin

Beno Ît Geslin

Nicolas Kaldonski

Thierry Tatoni

Impacts of Solar Energy on Butterfly Communities in Mediterranean Agro-Ecosystems

Keywords: landscape connectivity, species movements, circuit theory, least-cost modeling, life-history traits

The rapid expansion of Utility-Scale Solar Energy (USSE) is expected to meet economic and environmental challenges that society faces today and in the future. Yet there is a paucity of comprehensive research on biodiversity responses to USSE. Here we investigated the impact of USSE on species movements via the correlations between landscape connectivity modeling and the similarity of butterfly communities given their life-history traits. Our results suggest that mobile butterflies cope with USSE while interpatch movement of sedentary butterflies does not depend on landscape structure. We provide land-managers and energy-developers with an innovative tool to assess the ecological integration of USSE.

INTRODUCTION

With the expansion of global energy consumption and concerns over climate change [START_REF]Technology roadmap solar photovoltaic energy[END_REF], there has been a strong development of low-carbon energy technologies spurred by international policy drivers [2], such as Utility-Scale Solar Energy (USSE) (i.e., 1 MW capacity). Over the last decade, the cumulative photovoltaic capacity has grown at a rate of 49% per year worldwide [START_REF]Technology roadmap solar photovoltaic energy[END_REF].

Aside from the economic impacts of renewable energy sprawl, there is a paucity of empirical research on the environmental impacts of solar energy in peer-reviewed scientific journals [3-o ˆ5]. Information is mostly documented in "gray" literature [START_REF] Lovich | Wildlife conservation and solar energy development in the Desert Southwest, United States[END_REF] and publications detail a set of potential impacts of USSE that remains theoretical [START_REF] Tsoutsos | Environmental impacts from the solar energy technologies[END_REF][START_REF] Turney | Environmental impacts from the installation and operation of large-scale solar power plants[END_REF]. While several authors concluded in the minimal to positive environmental impacts of USSE [START_REF] Tsoutsos | Environmental impacts from the solar energy technologies[END_REF][START_REF] Turney | Environmental impacts from the installation and operation of large-scale solar power plants[END_REF], others such as [START_REF] Lovich | Wildlife conservation and solar energy development in the Desert Southwest, United States[END_REF][START_REF] Chiabrando | The territorial and landscape impacts of photovoltaic systems: Definition of impacts and assessment of the glare risk[END_REF] express concerns about their adverse impacts on biodiversity (e.g., habitat loss and fragmentation, alteration of habitat quality, species assemblage changes, microclimate disturbance, and species mortality) both from the installation and during operation phases. Hence, USSE may disrupt the movement of species across the landscape [START_REF] Lovich | Wildlife conservation and solar energy development in the Desert Southwest, United States[END_REF] due to reduced connectivity between populations.

In this context, further insights regarding the impact of USSE on biodiversity are needed as a basis for making appropriate siting decisions and mitigating potential environmental impacts. To address these challenges, focusing on landscape connectivity is of particular interest as connectivity may be a key to maintain biodiversity in fragmented landscapes [START_REF] Br€ Uckmann | Butterfly and plant specialists suffer from reduced connectivity in fragmented landscapes[END_REF]. Landscape connectivity is "the degree to which landscape facilitates or impedes movement of organisms among resource patches" [START_REF] Taylor | Connectivity is a vital element of landscape structure[END_REF]. For the purpose of assessing landscape connectivity, modeling the ecological cost of moving through the landscape (e.g., least-cost modeling, circuit theory) has been demonstrated to be more appropriate than Euclidean distances [11-o ˆ13]. Those techniques require resistance maps where a value for the reluctance to move throughout a land-use type is allocated to each pixel of a considered map. Therefore, circuit theory [START_REF] Mcrae | Isolation by resistance[END_REF] and in particular least-cost modeling [START_REF] Adriaensen | The application of "least-cost" modelling as a functional landscape model[END_REF] are popular resistance-based techniques to examine species' response to landscape heterogeneity [START_REF] Cushman | Biological corridors and connectivity[END_REF].

At the landscape scale, when two strongly linked patches exhibit similar communities in terms of composition, the spatial structure of species communities is then considered as a suitable proxy for estimating landscape connectivity [START_REF] Muratet | Evaluation of landscape connectivity at community level using satellite-derived NDVI[END_REF] which indirectly details species movement. Butterfly communities (Rhopalocera) are widely acknowledged in the literature to be sensitive to habitat fragmentation [START_REF] Ricketts | The matrix matters: Effective isolation in fragmented landscapes[END_REF]19] making them suitable models to study connectivity. Interestingly, as reviewed by Ref. [START_REF] Ewers | Confounding factors in the detection of species responses to habitat fragmentation[END_REF], species responses to habitat loss and fragmentation are mediated by their life-history traits; hence, specialists and sedentary butterfly species are predominantly affected by habitat fragmentation compared to generalists and mobile species [START_REF] Ekroos | Homogenization of lepidopteran communities in intensively cultivated agricultural landscapes[END_REF][START_REF] Villemey | Mosaic of grasslands and woodlands is more effective than habitat connectivity to conserve butterflies in French farmland[END_REF]. Therefore, discerning sedentary versus mobile species within butterfly communities may provide valuable information regarding the contrasting influence of landscape structure on movement patterns.

To our knowledge, assessing landscape connectivity at the level of species communities (see Refs. 17 and [START_REF] Gil-Tena | Woodland bird response to landscape connectivity in an agriculturedominated landscape: A functional community approach[END_REF]) has not yet been applied to addressing the environmental impacts of USSE. Our aim was to address the role of USSE on butterfly movements by investigating landscape connectivity at the community-level and given butterfly life-history traits. While studies mainly focus on high-conservation-value areas such as the deserts of the southwestern United States (see Refs. 3,24, and 25) here, we consider USSE as one of the landscape features among others within a humandominated landscape and qualify its role relatively to other landscape features given a gradient of anthropogenic pressures as proceeded by Ref. [START_REF] Liz Ee | Relative importance of habitat and landscape scales on butterfly communities of urbanizing areas[END_REF]. Ultimately, we provide energy-developers with a decision-support tool to mitigate the environmental impacts of USSE. Our basis hypotheses were that (i) two strongly linked habitats display similar butterfly communities, (ii) resistance-based algorithms would predict butterfly movement better than Euclidean distances, and (iii) there is a trait-mediated response to landscape structure, and in particular to USSE.

MATERIALS AND METHODS

Study Site

The study site is located in southeastern France (Puyloubier; 43830'N, 5839'E; Figure 1) and represents a 3 3 3 km window centered on a USSE. The facility was constructed in 2010 on a historically disturbed area, a former clay quarry and was thus not installed at the expense of a natural area. This ground mounted photovoltaic system extends over 18 ha with a capacity of 6.5 MW. The facility is embedded in a Mediterranean agro-ecosystem landscape dominated by vineyards (47.4% of the study site; average size of the vineyards: 2.3 6 3.4 ha), and interspersed with seminatural grasslands arising from the abandonment of agricultural land (14.4%; average size: 2.2 6 4.4 ha) and woody habitats colonized by Pinus halepensis (22.6%). Built areas represent 12.6% of the study site.

Parameterization of Resistance Values

Modeling landscape connectivity with resistance-based algorithms involves a Geographic Information System (GIS) approach (ArcGIS Desktop 10.2 [START_REF]ArcGIS Desktop: Release 10[END_REF]). Resistance maps were derived from the study site map (digitalization of aerial photographs supplemented with ground data that we collected in July 2015). We defined nine land-use types to carefully depict landscape heterogeneity (i.e., buildings, grassy field margins, roads, road verges, seminatural grasslands, USSE, vineyards, water, and woody habitats). We obtained a 1 m 3 1 m raster map that was converted into resistance maps. Setting resistance values for each land-use type proceeded from the existing scientific knowledge of the ecology and movement patterns of semigrassland butterflies. Land-use types promoting mobility were attributed lower resistance values than those impeding it. Therefore, the resistance value of seminatural grasslands, i.e., butterflies' habitat, was set to 1 (the lowest resistance). Knowing that grassy linear elements (road verges and grassy field margins) may be suitable for butterflies and act as habitats and/or corridors [28-o ˆ30], we assigned to these elements the lowest resistance value as well. Although most grassland butterflies typically avoid arable fields [31-o ˆ33], here, we assumed that vineyards could facilitate displacements given a particular management strategy (i.e., delayed mowing) that enables the occurrence of complementary flowering resources between the rows of vineyards (see Ref. 29). Munguira and Thomas [START_REF] Munguira | Use of road verges by butterfly and burnet populations, and the effect of roads on adult dispersal and mortality[END_REF] emphasize that common butterfly species may cope with roads (here, resistance value set to 1 due to small and low traffic roads). Conversely, impervious areas (buildings, water) and in particular, woody habitats prevent the movements of grassland butterfly species [START_REF] Ouin | Agricultural landscape connectivity for the meadow brown butterfly (Maniola jurtina)[END_REF][START_REF] Delattre | Grassy field margins as potential corridors for butterflies in agricultural landscapes: A simulation study[END_REF][START_REF] Kallioniemi | Inter-and intra-specific differences in butterfly behaviour at boundaries[END_REF]] and as such, received higher resistance values (2-100 times more resistant than seminatural grasslands). Finally, we attributed distinct resistance values to USSE ranging from 1 to 100. On this basis, we constructed eight resistance sets (Table 1 and Appendix A). We iteratively tested various combinations of resistance values to finely describe the relative contribution of each land-use type to butterfly movements (e.g., vineyards with varying resistance value 5 1/5/100).

Butterfly Sampling

We recorded the presence and abundance of butterfly species in 15 transects scattered across the study site (Figure 1). More specifically, five were chosen within seminatural grasslands, five within field margins, and five within road verges, respectively. Those transects needed to meet three criteria: they were placed (i) in homogeneous areas encompassing attractive flowering resources, (ii) at least 500 m away from the boundaries of the 3 3 3 km window of the study site, and (iii) at least 10 m away from a patch boundaries within seminatural grasslands [START_REF] Villemey | Mosaic of grasslands and woodlands is more effective than habitat connectivity to conserve butterflies in French farmland[END_REF]. Transects were located in the immediate vicinity and further from the solar power installation (from 30 to 830 m). None of them crossed the USSE area because we were denied access to the facility. Nevertheless, it would not significantly affect the quality of our analysis as we addressed interpatch movements rather than movements within patches. Operating short transect (25 m long 3 5 m wide) matched the width of grassy linear elements and ensured a sampling within homogeneous herbaceous cover as underlined by Ref. [START_REF] Liz Ee | Monitoring urban environments on the basis of biological traits[END_REF]. Transects were visited four times between 6 July and 28 August 2015 under optimal weather conditions [START_REF] Pollard | A method for assessing changes in the abundance of butterflies[END_REF]. We walked along the transects at a uniform pace during 5 min to record all butterflies seen within the transect.

Butterfly Community Similarity

We used the Morisita-Horn index [START_REF] Magurran | Ecological diversity and its measurements[END_REF] to describe butterfly communities based on the similarity of species composition between pairwise transects. This index, which uses relative rather than the absolute abundance of species between two communities, ranges from 0 (denoting no overlap between sites) to 1 (denoting that species occur in the same proportions in both sites). We selected this index because Magurran and Wolda [START_REF] Magurran | Ecological diversity and its measurements[END_REF][START_REF] Wolda | Similarity indices, sample size and diversity[END_REF] evidenced its relative robustness to species richness and sample sizes. To investigate landscape connectivity while using a trait-based approach, we divided butterfly communities in two levels of mobility: "sedentary" (low dispersal abilities) and "mobile" (higher dispersal abilities) following Ref. [START_REF] Villemey | Mosaic of grasslands and woodlands is more effective than habitat connectivity to conserve butterflies in French farmland[END_REF]. We referred to the mean dispersal distances of butterfly species predicted by Ref. [START_REF] Stevens | Dispersal syndromes and the use of life-histories to predict dispersal[END_REF]. A species was defined as "sedentary" if its mean dispersal distance was less than 254 m, i.e., the median of dispersal distances for all recorded species. Conversely, a species whose mean dispersal distance equaled or exceeded 254 m was "mobile." Species abundance was log(x 1 1)-transformed prior to calculations and pairwise similarity was then computed for both sedentary and mobile species using the "vegan" library in R 3.0.2. [START_REF]R: A language and environment for statistical computing[END_REF].

Calibration of Landscape Connectivity Modeling via the Butterfly Community Similarity

Least-cost modeling depicts the line that minimizes the cumulative cost of moving from a source to a destination patch [START_REF] Adriaensen | The application of "least-cost" modelling as a functional landscape model[END_REF] across a resistance map. Each pixel of the resistance map is assigned a value of the reluctance to move throughout a given land-use type. Least-cost modeling assumes that organisms have a complete knowledge of the landscape which enables them to follow the cheapest route. In the view of investigating conceptually distinct modeling approaches of landscape connectivity, circuit theory [START_REF] Mcrae | Isolation by resistance[END_REF] is another common algorithm. Landscape is thus converted into an electrical circuit, i.e., a network of regularly spaced electrical nodes connected by resistors, whose values are defined by the resistance map. Resistors oppose the flow of electrical current (i.e., movement of organisms). Circuit theory would give convincing results because it complements the single least-cost path by multiple pathways presumably undertaken by moving organisms preferring low-resistance habitats [START_REF] Mcrae | Using circuit theory to model connectivity in ecology, evolution, and conservation[END_REF]. For both least-cost modeling and circuit theory, the effective distance is then a measure of isolation or movement cost between pairs of patches; but according to circuit theory, it decreases as more pathways with low resistance connect pairwise patches [START_REF] Mcrae | Using circuit theory to model connectivity in ecology, evolution, and conservation[END_REF]. We computed least-cost modeling and circuit theory on all 1 m 3 1 m resistance maps using algorithms implemented in the Cost distance and Circuitscape 4.0 toolboxes in ArcGIS Desktop 10.2, respectively. Points source and destination corresponded to the center of each transect. After application of both resistance-based algorithms, we obtained effective distances between pairwise transects. Then, we examined the correlations between the landscape connectivity models predicting intertransect effective or Euclidean distances and log(x 1 1)-transformed Morisita-Horn index, using generalized linear models (GLMs) (normal distribution, log-link function). We restricted the analysis to pairwise transects which were distant up to 1100 m in a straight line (i.e., approximating the highest mean dispersal distance for all recorded butterflies). To select the best predictive model of the similarity for sedentary and mobile communities, we used Akaike's information criterion corrected (AICc) for small sample size. Following the rule of DAICc 2, models were less supportive of our empirical data if their relative difference of AICc to the best model exceeded 2. The selection procedure was strengthened by model probabilities (xi) and evidence ratios calculated using "AICcmodavg" package in R [START_REF] Burnham | AIC model selection and multimodel inference in behavioral ecology: some background, observations, and comparisons[END_REF]. We checked the significance of each GLM based on 10,000 permutations, as pairwise similarities and effective/Euclidean distances were statistically dependent. The statistical analyses were performed in R 3.0.2.

RESULTS

We recorded 267 mobile individuals and 491 sedentary individuals of 24 butterfly species (Appendix B). For mobile species, the Morisita-Horn index between pairwise transects was best predicted by effective distances calculated from RS8 implemented in circuit theory (model 16; Table 2). This resistance set indicated that the USSE was as easy to traverse as seminatural grasslands and grassy linear elements. The model explained 25.7% of the deviance. Butterfly community For sedentary species, model 26 (RS4 in circuit theory) detected that on average the similarity of butterfly communities had a tendency to decrease with increasing effective distances without being significant (P value 5 0.115). This model indicated that USSE is 100 times more resistant than open-habitats while woody habitats are 2 times more resistant than open-habitats. It explained 4.93% of the deviance. However, as stated, the first ranked-model was not significantly more discriminatory than alternative models of landscape connectivity (low model probabilities: x i 0.11 and models displayed DAICc 2.49; Table 2). Evidence ratios were particularly weak (ranging from 1.17 to 3.47). In addition, the second model of landscape connectivity that best explained the spatial structure of butterfly communities was the null model.

DISCUSSION

We propose here a tool providing comprehensive information on how species perceive USSE. We demonstrated that mobile butterfly species cope with this man-made facility while landscape structure does not modulate the spatial structure of sedentary species communities.

Contribution of Landscape Connectivity: Unraveling the Role of USSE for Butterfly Movements

Our results indicate that for mobile species, two strongly linked transects tend to display similar butterfly communities (as expected in our basis hypothesis) while none of our models was statistically significant for sedentary species. Despite a simple parameterization of resistance sets, circuit theory outperformed other modeling approaches, i.e., leastcost and Euclidean distance (corroborating hypothesis 2). Multiple pathways between pairwise transects may improve the predictive power of our landscape connectivity models compared to the popular least-cost modeling (see Refs. 11 and [17] on other species groups), because it may bring more ecologically realistic information on how landscape structure shapes the movement of organisms than a single least-cost path model, in particular for species with high dispersal abilities. Knowing that the similarity of mobile butterfly communities is a reasonable proxy for landscape [START_REF] Sutcliffe | Modelling the benefits of farmland restoration: Methodology and application to butterfly movement[END_REF]. We have also contributed to improving the understanding of the connectivity of grassland butterflies, and more specifically the impact of facilities such as USSE in humandominated landscapes. The best resistance set (RS8) reports that USSE did not impede the movement of mobile butterfly species. Those species seemed to display a stronger propensity to move via seminatural grasslands, grassy linear elements, vineyards, and USSE rather than woody habitats and impervious surfaces within a human-dominated context. Grasslands and grassy linear elements indicate the lowest resistance because they provide both habitats [START_REF] Flick | Effects of landscape structure on butterfly species richness and abundance in agricultural landscapes in eastern Ontario, Canada, Agriculture[END_REF] and complementary resources [START_REF] Ouin | Complementation/supplementation of resources for butterflies in agricultural landscapes[END_REF]. The role of grassy linear elements as corridor-structures for butterflies moving between distant grassland patches is widely acknowledged in the literature [START_REF] Delattre | An agrienvironmental scheme enhances butterfly dispersal in European agricultural landscapes[END_REF][START_REF] Delattre | Grassy field margins as potential corridors for butterflies in agricultural landscapes: A simulation study[END_REF][START_REF] Ries | Conservation value of roadside prairie restoration to butterfly communities[END_REF]. Here traversing one pixel of USSE is 100 times less costly than one of woody habitats which have previously been cited as dispersal barriers for open habitat butterflies [START_REF] Ouin | Agricultural landscape connectivity for the meadow brown butterfly (Maniola jurtina)[END_REF][START_REF] Kallioniemi | Inter-and intra-specific differences in butterfly behaviour at boundaries[END_REF]. The delayed mowing (up to August) both between rows of vineyards and of solar panels enables the occurrence of flowering resources even during the drought season, which may in turn limit the resistance values of both USSE and vineyards (see RS6, RS7). Liz ee et al. [START_REF] Liz Ee | Relative importance of habitat and landscape scales on butterfly communities of urbanizing areas[END_REF] emphasized that vineyards located in peri-urban Mediterranean agro-ecosystems were not harmful for butterfly movements. Conversely, no evidence was found that landscape structure influences sedentary species (yet their abundance was twice as high as that of mobile species). This result is inconsistent with the literature that emphasizes the detrimental effects of habitat fragmentation on poorly mobile species [START_REF] Ekroos | Homogenization of lepidopteran communities in intensively cultivated agricultural landscapes[END_REF][START_REF] Villemey | Mosaic of grasslands and woodlands is more effective than habitat connectivity to conserve butterflies in French farmland[END_REF] but it may reflect the sufficient availability of resources within contemporary open habitats; therefore, sedentary butterflies remain in place. Conversely, we assume that a strong disturbance in these open habitats due to land-use changes would have affected the spatial structuration of sedentary butterfly communities. Furthermore, since sedentary butterflies move over limited distances, the similarity of communities could mainly result from local factors such as particular habitat or resources (e.g., significance of local conditions for sedentary species richness [START_REF] Ockinger | Mobility-dependent effects on species richness in fragmented landscapes[END_REF]) rather than isolation between habitat patches. Alternative explanations relate to (i) the spatial extent at which species respond to landscape structure that was too large to properly address ecological processes [START_REF] Flick | Effects of landscape structure on butterfly species richness and abundance in agricultural landscapes in eastern Ontario, Canada, Agriculture[END_REF] or (ii) the parameterization of resistance sets that inaccurately reflects how sedentary species perceive the spatial arrangement of land-use types.

In accordance with the studies of Refs. 17 and [START_REF] Gil-Tena | Woodland bird response to landscape connectivity in an agriculturedominated landscape: A functional community approach[END_REF] conducted on birds and plant communities, we highlight that community similarity is a reasonable proxy for landscape connectivity, and here, given species life-history traits. The trait-mediated response to landscape structure (hypothesis 3) has been widely reported in the literature (sedentary/mobile, generalist/specialist [START_REF] Br€ Uckmann | Butterfly and plant specialists suffer from reduced connectivity in fragmented landscapes[END_REF][START_REF] Villemey | Mosaic of grasslands and woodlands is more effective than habitat connectivity to conserve butterflies in French farmland[END_REF][START_REF] Ockinger | Life-history traits predict species responses to habitat area and isolation: A cross-continental synthesis[END_REF] but we provide new evidences regarding the impact of USSE on butterfly communities to thus qualify its role on species movement. One of the interests of our study lies in the development of a cost-effective modeling approach validated by empirical data that improves our understanding of the ecological integration of USSE as an alternative to labor-extensive fieldwork methods (e.g., mark-release-recapture, recording flight paths [START_REF] Ouin | Agricultural landscape connectivity for the meadow brown butterfly (Maniola jurtina)[END_REF][START_REF] Loos | Changes in butterfly movements along a gradient of land use in farmlands of Transylvania (Romania)[END_REF]).

Limitations and Perspectives

Although our methodology underlines to a certain extent the influence of landscape structure on butterfly communities, we suggest to (i) increase the number of nearby transects (to statistically analyze processes at finer scales, which would be more appropriate for sedentary species) and (ii) improve the a priori assignment of resistance sets via quantitative estimates inferred from biologically meaningful data [START_REF] Zeller | Estimating landscape resistance to movement: A review[END_REF], which would however involve labor-intensive fieldwork. (iii) The binary distinction of "sedentary" and "mobile" species based on median dispersal distance may be questionable for experts (e.g., Colias crocea being a migratory species should appear as "mobile" rather than "sedentary"). Nevertheless, we believe that here, the wide range of dispersal distances guarantees a relatively consistent distinction of butterfly species. (iv) Among the overriding factors that influence butterfly communities (diversity, abundance), it may be appropriate to encompass local factors such as patch size and habitat quality (nectar and/or larval host-plants resources, direct management practices [50-o ˆ52]), especially for sedentary species. (v) Moreover, Refs. 22 and [52] emphasized that grassland butterfly communities could benefit from the complementary resources provided by forests and particularly forest edges (nectar, host plants, and shelter) which, coupled with the trait-mediated edge effect on organisms' behaviors [START_REF] Ries | Butterfly responses to habitat edges in the highly fragmented prairies of Central Iowa[END_REF], highlights the need to account for a varying edge resistance to improve landscape connectivity modeling. (vi) Finally, local and long-term experimental studies have to be conducted to determine the effects of fences and management strategies on biodiversity within USSE.

CONCLUSIONS AND POLICY IMPLICATIONS

Our study is part of an integrative approach confounding the planning, socioeconomic and environmental aspects of solar energy. Here, we fill the gap between biodiversity conservation and solar energy sprawl with an empirically validated modeling approach addressed to coworking energydevelopers and land-managers for a proactive thinking which will (i) provide on-site mitigation measures and (ii) guide siting decisions.

Given our findings and the ecology of grassland butterflies, we may emphasize a wide range of policy recommendations to enhance the environmental quality of USSE: (i) to revegetate areas between and under rows of solar panels once installed; (ii) to adapt the frequency of mowing to plant phenology; and (iii) to increase both the diversity of host plant species and the cover of flowering resources. Furthermore, siting-decisions could greatly benefit from the presented tool as it complements multicriteria GIS analysis conducted at regional scale to identify large potential areas for the implementation of solar energy [START_REF] Cameron | An approach to enhance the conservation-compatibility of solar energy development[END_REF][START_REF] Stoms | Siting solar energy development to minimize biological impacts[END_REF][START_REF] Fluri | The potential of concentrating solar power in South Africa[END_REF][START_REF] Watson | Regional scale wind farm and solar farm suitability assessment using GIS-assisted multi-criteria evaluation[END_REF] with consistent empirical data on how species mobility would be locally affected by USSE. To a certain extent, installing USSE on disturbed areas may limit the range and intensity of environmental impacts. Hence, the implementation of the studied USSE on a former clay quarry may explain why mobile butterflies perceive this facility as highly permeable. Inversely, we suggest that its installation on locally rich habitats would have been highly detrimental to butterfly communities, and particularly to sedentary species. To provide a clearer insight on this point, we must analyze the environmental impacts of a gradient of USSE installed in various habitats, and over time. In the upcoming years, industrials would be likely to work hand in hand with scientists to conduct BACI experiments (Before-After, Control-Impact) that would give qualitative and quantitative information to understand how biodiversity is affected by a new facility.

Here, we meet the need for a robust assessment of environmental impacts that is likely to be required in environmental compliance documents and ease the process of planning permission. We developed a pro-active method transferable to other renewable as well as conventional energy facilities, thus providing insights regarding their environmental impacts.

Figure 1 .

 1 Figure 1. Localization of the study site (SE France) (left) and presentation of the sampling design with utility-scale solar energy (hatched in black) and the positioning of our 15 transects (white stars; right).

Table 1 .

 1 Resistance sets implemented into landscape connectivity algorithms. For example, for RS2, USSE is 15 times more resistant than open-habitats (value 5 1) and 6.7 times less resistant than woody habitats (value 5 100).

	Land-use types	RS1	RS2	RS3	RS4	RS5	RS6	RS7	RS8
	Buildings	100	100	100	100	100	100	100	100
	Grassy field margins* USSE	100	15	40	100	100	1	1	1
	Vineyards	1	1	1	1	100	1	1	5
	Water	100	100	100	100	100	100	100	100
	Woody habitats	100	100	100	2	100	100	20	100
	*Grassy linear elements.

Environmental Progress & Sustainable Energy (Vol.00, No.00) DOI 10.1002/ep

Table 2 .

 2 Results of the GLMs analyses for mobile and sedentary species. RS: Resistance set; AICc: Akaike information criterion corrected; x i : probability of the model i (Akaike weight).

				Modeling				Evidence
		Model	RS	approach	AICc	DAICc	x i	ratio
	Mobiles species	1	1	Least-cost	219.37	12.1	0	423.1
		2	1	Circuit theory	227.16	4.31	0.05	8.6
		3	2	Least-cost	219.36	12.1	0	425.0
		4	2	Circuit theory	227.82	3.64	0.08	6.2
		5	3	Least-cost	219.36	12.1	0	425.0
		6	3	Circuit theory	227.38	4.09	0.06	7.7
		7	4	Least-cost	220.6	10.86	0	228.7
		8	4	Circuit theory	222.56	8.91	0.01	86.2
		9	5	Least-cost	220.55	10.92	0	234.6
		10	5	Circuit theory	217.92	13.55	0	877.1
		11	6	Least-cost	219.36	12.11	0	425.9
		12	6	Circuit theory	229.42	2.05	0.17	2.8
		13	7	Least-cost	221.54	9.93	0	143.4
		14	7	Circuit theory	229.17	2.3	0.15	3.2
		15	8	Least-cost	221.2	10.27	0	170.2
		16	8	Circuit theory	231.47	0	0.47
		17		Null model	218.58	12.89	0	629.7
		18		Euclidean distance	220.47	10.99	0	244.0
	Sedentary species	19	1	Least-cost	8.67	1.72	0.04	2.37
		20	1	Circuit theory	7.51	0.57	0.08	1.33
		21	2	Least-cost	8.66	1.72	0.04	2.36
		22	2	Circuit theory	7.71	0.77	0.07	1.47
		23	3	Least-cost	8.66	1.72	0.04	2.36
		24	3	Circuit theory	7.58	0.64	0.08	1.38
		25	4	Least-cost	8.73	1.79	0.04	2.45
		26	4	Circuit theory	6.94	0	0.11
		27	5	Least-cost	9.43	2.49	0.03	3.47
		28	5	Circuit theory	8.21	1.27	0.06	1.88
		29	6	Least-cost	8.63	1.68	0.05	2.32
		30	6	Circuit theory	8.31	1.36	0.05	1.98
		31	7	Least-cost	9.16	2.22	0.03	3.03
		32	7	Circuit theory	7.81	0.86	0.07	1.54
		33	8	Least-cost	8.56	1.61	0.05	2.24
		34	8	Circuit theory	9.33	2.38	0.03	3.29
		35		Null model	7.26	0.32	0.09	1.17
		36		Euclidean distance	9.13	2.19	0.04	2.98

Environmental Progress & Sustainable Energy (Vol.00, No.00) DOI 10.1002/ep

ACKNOWLEDGMENTS

This study was funded by the programme "Processus d'Int egration Ecologique de l'Energie Solaire" (PIESO) (Grant Environmental Progress & Sustainable Energy (Vol.00, No.00) DOI 10.1002/ep Month 2017 5

No. CT2201TTADEM0). We would like to thank field assistants for their help and Michael Paul for greatly improving the English of this paper (No. 4500241987). We are grateful for the assistance of Nicolas Maurel on butterfly species identification.