Simplification of shade tree diversity reduces nutrient cycling resilience in coffee agroforestry

1. Agroforestry systems are refuges for biodiversity and provide multiple ecosystem functions and services. Diverse multispecies shade tree canopies are increasingly replaced by monospecific shade, often dominated by non-native tree species. The loss of tree diversity and the nature of the dominating tree can have strong implications for ecosystem functions, e.g. nutrient cycling ultimately reducing crop production. 2. To understand direct and indirect impacts of shade trees on nutrient cycling and crop production, we studied coffee agroforestry systems in India along a gradient from native multispecies canopies to Grevillea robusta (Proteaceae) -dominated canopy cover. We identified 25 agroforests, across a broad rainfall and management gradient and assessed litter quantity and quality, decomposition, nutrient release, soil fertility and coffee nutrient limitations. 3. Increasing G. robusta dominance affected nutrient cycling predominantly by; (1) changing of litter phenology, (2) red...