In the past 30 years, the notion of landscape has emerged in ecology as a result of both theoretical considerations and practical aspects of land use and land cover. This has generated a variety of numerical models addressing both methodological and thematic objectives. Scientists model landscapes for at least two reasons: to better understand the landscape dynamics themselves (called intrinsic needs) and to offer a realistic frame to support other ecological processes (extrinsic needs). This paper mainly concerns the intrinsic needs; it reviews and discusses the way the socioeconomic and/or ecological mechanisms of various landscapes have been explored through modelling approaches in the past. Our objective is to identify the possible lack of understanding in landscape dynamics and to propose a unified view of this complex object. We outline the links between the concepts of landscape and of models using a double-entry matrix, focusing on one hand on the four main terrestrial landscapes (agricultural, forested, arid and urban) and on the other hand on the main landscape model characteristics (explicit or neutral, patchy or continuous, and multi-or mono-scale). The patterns and processes of each of the four landscape types, in particular, are analysed within a coherent framework. The heterogeneity of this yet coherent analytical matrix implies the need for unifying concepts and formalisms. The complexity theory and related concepts such as self-organization or formal grammar applied to landscape mosaics could help to further develop the mathematical formalisms necessary to assemble the various inner landscape processes. The discipline can now offer a theoretical dimension to dynamic landscape modelling aiming at understanding the mechanism unity underlying this complex object.

Individual variability generally exists in crop fields. It increases with an increase in plant population density, water or nutrient deficiency, or spatio-temporal irregularity, and often results in a reduction in yield. As individual variability exists in a community but is expressed through individuals, we studied it by applying two models, one at the stand level and the other at the individual level.The crop model PILOTE and the functional structural plant model (FSPM) GreenLab were applied to a field of maize (Zea mays L.) to provide a numerical description of the crop at different levels. The delay and slower increase in LAI and in total dry matter at stand level compared to individual level, led us to hypothesize that uneven emergence could have an effect on variability. We derived a theoretical distribution of germination dates, which supported this hypothesis. In parallel, we used GreenLab to analyze possible sources of variability in accumulated biomass within a dynamic system, and to estimate possible parameters from experimental data.Using PILOTE and GreenLab, we successfully identified two typical types of individual variability in the maize field: variability in development over time and variability in competition for space during growth. Our method could be used in future research on the cause and influence of individual variability on performance, and to identify the link between an FSPM based on individual plants and a crop model at stand level. (C) 2013 Elsevier B.V. All rights reserved.

Forest stand dynamics models simulate the growth of trees in stands; based on field measurements and system knowledge, they provide a relatively precise representation of forest growth and are well adapted for forest management purposes. Architectural models describe the structure of plants according to ontogenetic development processes; as a support of biomass production and partitioning at organ scale, they simulate individual tree development.

published or not.The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.Copyright The CAQ network in France: 15 years of brainstorming and cooperative work to connect forest resources and wood quality through modelling approaches and simulation software

Modelling annual shoot development processes is a key step towards functional–structural modelling of trees. Various patterns of meristem activity can be distinguished in tree shoots, with active periods of phytomer production followed by rest periods. This approach has seldom been integrated in functional–structural tree models.

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.

The present work describes a landscape visualization tool which has been developed within the SEAMLESS project. This landscape visualization component should be launched at the end of a policy simulation to allow for exploration of landscape changes, as a post-model analysis, to be used as a basis for discussion and negotiation within the community.

In agroforestry systems, the distribution of light transmitted under tree canopies can be a limiting factor for the development of intercrops. The light available for intercrops depends on the quantity of light intercepted by tree canopies and, consequently, on the architecture of the tree species present. The influence of tree architecture on light transmission was analysed using dynamic 3D architectural models. The architectural analysis of Acacia mangium and Tectona grandis was performed in Indonesian agroforestry systems with trees aged from 1 to 3 years. 3D virtual trees were then generated with the AmapSim simulation software and 3D virtual experiments in which tree age, planting density, planting pattern and pruning intensity varied were reconstructed in order to simulate light available for the crop. Canopy closure of trees was more rapid in A. mangium than in T. grandis agroforestry systems; after 3 years the quantity of light available for A. mangium intercrops was three times lower than under T. grandis. Simulations with A. mangium showed that practices such as pruning and widening tree spacing enable to increase the total transmitted light within the stand. On T. grandis, modification of the tree row azimuth resulted in changes in the spatial and seasonal distribution of light available for the intercrops. These results are discussed in terms of agroforestry system management.

Endogenous variations in the annual growth of trees suggest that similar trends would occur in phyllodes. In comparison to leaves, the characteristics of phyllodes are less well known, hence this study examines the effects of architectural position and age of tree on the phyllodes of Acacia mangium. Phyllodes were investigated on 1-, 2-, and 3-year-old trees from three axis positions within the crown. We focused on the morphological, optical and biochemical traits of the phyllodes. The increase in phyllode area and lamina thickness is more pronounced in the older trees. Leaf mass area (LMA), stomatal density, nitrogen and chlorophyll content increase with tree age. The values of these characteristics decrease from the main stem to the lower branches for the older trees. Phyllode light absorptance increased with tree age whereas reflectance was higher for the upper position compared to the lower position within the crown. Carotenoid content and chlorophyll a/b ratio were higher for the younger phyllodes of younger trees. Increasing tree size induced modifications in the phyllode characteristics which are influenced by both morphogenetic and light gradients within the crown. This study demonstrated pronounced changes in terms of morphological and functional indicators of photosynthetic capacity in relation to phyllode position within the crown and to tree age. These morphogenetic effects on the phyllode characteristics should be taken into account in studies on phenotypic plasticity.

A stochastic functional–structural model simulating plant development and growth is presented. The number of organs (internodes, leaves and fruits) produced by the model is not only a key intermediate variable for biomass production computation, but also an indicator of model complexity. To obtain their mean and variance through simulation is time-consuming and the results are approximate. In this paper, based on the idea of substructure decomposition, the theoretical mean and variance of the number of organs in a plant structure from the model are computed recurrently by applying a compound law of generating functions. This analytical method provides fast and precise results, which facilitates model analysis as well as model calibration and validation with real plants. Furthermore, the mean and variance of the biomass production from the stochastic plant model are of special interest linked to the prediction of yield. In this paper, through differential statistics, their approximate results are computed in an analytical way for any plant age. A case study on sample trees from this functional–structural model shows the theoretical moments of the number of organs and the biomass production, as well as the computation efficiency of the analytical method compared to a Monte-Carlo simulation method. The advantages and the drawbacks of this stochastic model for agricultural applications are discussed.

In an agroforestry context, the knowledge of leaf area is an important parameter to take into consideration because tree foliage shades the intercrop. Single leaf measurement (for example leaf length and width) is a widely used method to estimate leaf area in a rapid non-destructive way. In this study, the objectives were to estimate the leaf area of different leaf sizes and shapes for Acacia mangium Willd. (Mimosaceae), Tectona grandis L. (Verbenaceae), Hevea brasiliensis Muell.-Arg. (Euphorbiaceae), and Swietenia macrophylla King. (Meliaceae) Indonesian agroforestry trees. In order to characterise leaf area in field conditions a digital photograph method was used. Leaf length was measured in order to build relationships between leaf length versus actual leaf area. Additional measurements obtained from the digital pictures such as lamina width, number of leaflets, leaflet length and width were recorded in order to test the benefit regarding leaf area estimation based only on the leaf length model. The combination of these different linear leaf measurements led to various degrees of precision of leaf area estimation. The different models can then be chosen according to a compromise between the accuracy of leaf area estimation and the time allocated to field measurements.