Toward Modelling of Transformational Change Processes in Farm Decision-Making

In the coming decades, agricultural systems will have to adapt to tremendous challenges. Behavioral models have important potential to better understand and steer changes toward sustainability brought about by this context. Relying on a literature review, we distinguish incremental changes (extensions of what is already done) and transformational changes, which involve the reorientation of a considerable amount of farming activities. Transformational changes are particularly important in the context of global change. Existing integrated modelling frameworks based on behavioral theories are suited for incremental changes, but remain limited for transformational changes. Qualitative studies provide important insights on two key aspects of transformational changes, learning and social relations, but they have not been explicitly oriented toward computer modelling yet. Based on this literature and three seminal decision-making approaches, we propose a description of transformational change processes in farm decision-making, as a first step toward an implementation in agent-based models.

Inter- and intraspecific variability of plant individual growth and its role on species ranking in grasslands

Aims Individual growth constitutes a major component of individual fitness.However,measuring growth rates of herbaceous plants non-destructively at the individual level is notoriously difficult.This study,based on an accurate non-destructive method of aboveground biomass estimation,aims to assess individual relative growth rates(RGRs)of some species,identify its environmental drivers and test its consequences on community patterning.We specifically address three questions:(i)to what extent environmental conditions explain differences in individual plant growth between sites,(ii)what is the magnitude of intraspecific variability of plant individual growth within and between sites and(iii)do species-averaged(dis-)advantage of individual growth compared with the whole vegetation within a site correlate with species ranking at the community level?Methods We monitored the growth of individuals of four common perennial species in 18 permanent grasslands chosen along a large pedoclimatic gradient located in the Massif Central,France.We measured soil properties,levels of resources and meteorological parameters to characterize environmental conditions at the site level.This design enables us to assess the influence of environmental conditions on individual growth and the relative extent of inter-individual variability of growth explained within and between sites.We determined the ranking of each of the four species in each site with botanical surveys to assess the relationship between species-averaged growth(dis-)advantage relative to the whole community and species rank in the community.Important Findings We found that environmental conditions explain a significant proportion of individual growth variability,and that this proportion is strongly variable between species.Light availability was the main driver of plant growth,followed by rainfall amount and potential evapotranspiration,while soil properties had only a slight effect.We further highlighted a moderate to high within-site inter-individual variability of growth.We finally showed that there was no correlation between species ranking and species-averaged individual growth.