Classification of Pulses Diversity for the Provision of Three Ecosystems Services: Nitrogen Fixation, Weed Suppression, and Production Under Dry Conditions

Grain legumes meet several agricultural challenges in the perspective of ecological intensification: not only they have the ability to fix atmospheric nitrogen, which make them highly suitable for lowinput system and lead to reduced energy use, but also they can deliver other services. They represent affordable sources of protein for human consumption and a source of diversification to break pest and weeds cycles and optimize nutrient management. However, the specific diversity of pulses is poorly represented in most cropping systems despite the growing demand from food chains. While over than 80 pulses are consumed by humans, the FAO database covers only 11 pulse species. The number of released cultivars is also very low: in France, for example, only 7 chickpeas cultivars are available in the French market, while more than 90,000 accessions are recorded in the world’s genetic resources. The objective of this study is to characterize the genetic diversity of a wide range of species and varieties of pulses through a functional approach that links agro-morphological traits, physiological functions and ecosystem services. Three ecosystem services have been identified as crucial for Mediterranean cropping systems: 1) yield production and stability under dry conditions (i.e; drought resistance), 2) nitrogen fixation and accumulation in the plant for future return to the soil, and 3) competitiveness toward weeds. An extensive literature review (120 ref.) allowed us to identify and document 41 species regarding a set of 12 traits (e.g. maximum plant height, leaf size, days to maturity…). The full data was then analyzed with CART regressions. As an example, drought resistance was well predicted by the maximum height, day to flowering, seed size, and leaf size. Plants with small leaves, short cycles and short height are most likely to be more resistant than others. Species were then assembled into groups of species with similar patterns of ecosystem services, according to their agro-morphological traits. These results allow a better understanding of how specific diversity of grain legumes is organized and can be used with respects to target ecosystem services.