Sébastien Griffon

Virtual reality for cultural landscape visualization

Although land managers and policy-makers generally have a good experience of what result can be expected from their decisions, they are often faced with difficulty when trying to communicate the visual impact of a management option to stakeholders, particularly when the landscape exhibits a high cultural value. Three-dimensional visualization of the landscape is often used for communicating with the stakeholders. A challenge in participatory methods for integrated assessment and policy planning is to view future changes in land use, according to scenarios. A 3-D landscape visualization component, SLE (“Seamless Landscape Explorer”), has been developed, which is launched after a scenario simulation to allow for exploration of landscape changes. Pressures causing such changes are translated into changes in the spatial configuration of the landscape. The different types of land-use are visualized thanks to a library of detailed textures, and vegetation can be added. This has been applied to a study of four scenarios in the French Mediterranean region, which were set up as part of a participatory process for discussing the planning of the regional peri-urban and agricultural policy, in an area dominated by the typical culturally sensitive Mediterranean matorral, (“garrigue” shrubland) surrounding the Pic Saint-Loup mountain. Examples of visualization are shown and discussed here.

Visualising Changes in Agricultural Landscapes

Although land managers and policy-makers generally have a good experience of what result can be expected from their decisions, they are often faced with difficulty when trying to communicate the visual impact of a future management option to all stakeholders (local and regional decision-makers, land managers, landscape planners, and various communities involved in outdoor activities). Three-dimensional visualisation of the landscape is often used for communicating with the stakeholders. Static, web-based landscape visualisation tools have made considerable progress in recent years, such as for example Google Earth, covering the entire planet in 3D. Such visualisations are based on aerial (satellite) imagery, at a specific date, but are not dynamic. The challenge in methods for integrated assessment of agricultural systems (such as developed in SEAMLESS) is to view future changes in land use, according to scenarios.

A Forest Growth Simulator Based on Functional-Structural Modelling of Individual Trees

The objective of this paper is to study forest growth simulation based on functional-structural modelling and its potentials for forestry applications. The GreenLab model is used for this purpose owing to its computational performances, its calibration capacity on real plants and its extension to the stand level, by taking into account the competition between neighbouring plants and the interactions with the environment. We first propose a software design: - to manage the composition of forest scenes, - to simulate their growth based on parallel computing of individual trees with the GreenLab model, - to get the realistic and real-time 3D rendering of the simulation results. We then detail a test case to illustrate the potentialities of this new tool. Mono-specific stands of poplars and pines are simulated. We analyze the computation performances and illustrate the simulation results with 3D outputs. A very classical application in forest management, stand thinning, is also tested. Our tool provides new insights thanks to the detailed architectures of trees resulting from the functional-structural model.

Integrating mixed-effect models into an architectural plant model to simulate inter- and intra-progeny variability: a case study on oil palm (Elaeis guineensis Jacq.)

Three-dimensional (3D) reconstruction of plants is time-consuming and involves considerable levels of data acquisition. This is possibly one reason why the integration of genetic variability into 3D architectural models has so far been largely overlooked. In this study, an allometry-based approach was developed to account for architectural variability in 3D architectural models of oil palm (Elaeis guineensis Jacq.) as a case study. Allometric relationships were used to model architectural traits from individual leaflets to the entire crown while accounting for ontogenetic and morphogenetic gradients. Inter- and intra-progeny variabilities were evaluated for each trait and mixed-effect models were used to estimate the mean and variance parameters required for complete 3D virtual plants. Significant differences in leaf geometry (petiole length, density of leaflets, and rachis curvature) and leaflet morphology (gradients of leaflet length and width) were detected between and within progenies and were modelled in order to generate populations of plants that were consistent with the observed populations. The application of mixed-effect models on allometric relationships highlighted an interesting trade-off between model accuracy and ease of defining parameters for the 3D reconstruction of plants while at the same time integrating their observed variability. Future research will be dedicated to sensitivity analyses coupling the structural model presented here with a radiative balance model in order to identify the key architectural traits involved in light interception efficiency.

AMAPstudio: A software suite for plants architecture modelling

AMAPstudio is a user-friendly software suite designed for botanists and agronomists to edit, visualize, explore and simulate multi-scale plant architecture. It contains interactive tools to handle the topology (e.g. organs addition or deletion), the geometry (e.g. 3D selection, edition, rotation) and the dynamics (i.e. time line, scenarios) of plants at the individual or scene scale. AMAPstudio is based on the Multi-scale Tree Graph (MTG) data structure, which is commonly used to represent plant topology. Users can explore this data structure to test or to improve hypotheses on plant development. Specific data can be extracted with combinations of criteria and can be visualized in tables and graphs. Simple analysis functions can be launched or data can be exported to external tools, e.g. R, or any other statistical computing environment, for more specific analyses. AMAPstudio is also a framework in which modellers can integrate their own plant simulation models. Different scenarios can be computed for a growth model by interactively modifying model parameters or plant structure (e.g. by pruning) at particular time steps.

Using terrestrial laser scanning data to estimate large tropical trees biomass and calibrate allometric models: A comparison with traditional destructive approach

Summary 1.Calibration of local, regional or global allometric equations to estimate biomass at the tree level constitutes a significant burden on projects aiming at reducing Carbon emissions from forest degradation and deforestation. The objective of this contribution is to assess the precision and accuracy of Terrestrial Laser Scanning (TLS) for estimating volumes and aboveground biomass (AGB) of the woody parts of tropical trees, and for the calibration of allometric models. 2.We used a destructive dataset of 61 trees, with diameters and AGB of up to 186.6 cm and 60 Mg respectively, which were scanned, felled and weighed in the semi-deciduous forests of eastern Cameroon. We present an operational approach based on available software allowing to retrieve TLS volume with low bias and high accuracy for large tropical trees. Edition of the obtained models proved necessary, mainly to account for the complexity of buttressed parts of tree trunks, which were separately modelled through a meshing approach, and to bring a few corrections in the topology and geometry of branches, thanks to the AMAPStudio-Scan software. 3.Over the entire dataset, TLS derived volumes proved highly reliable for branches larger than 5 cm in diameter. The volumes of the remaining woody parts estimated for stumps, stems and crowns as well as for the whole tree proved very accurate (RMSE below 2.81% and R² above of 0.98) and unbiased. Once converted to AGB using mean local specific wood density values, TLS estimates allowed calibrating a biomass allometric model with coefficients statistically undistinguishable from those of a model based on destructive data. Un-edited Quantitative Structure Model (QSM) however lead to systematic overestimations of woody volumes and subsequently to significantly different allometric parameters. 4.We can therefore conclude that the non-destructive TLS approach can now be used as an operational alternative to traditional destructive sampling to build the allometric equations, although attention must be paid to the quality of QSM model adjustments to avoid systematic bias. This article is protected by copyright. All rights reserved.