Background/Question/Methods Strategic management of plant functional diversity is the cornerstone of agricultural management systems seeking to enhance agroecosystem function, expand the provision of ecosystem services and reduce dependence on chemical inputs. Organic agriculture is particularly dependent on using plant biodiversity to provide supporting ecosystem services because the use of conventional fertilizers and other chemicals is forbidden. A great deal of attention has focused on the capacity of plant diversity to provide aboveground ecosystem services such as pollination and pest control. The role of plant diversity in supporting ecosystem services provided by belowground processes has received less attention. This presentation will focus on the role of plant species diversity in providing complex, belowground ecosystem services. Results/Conclusions First, I will briefly discuss the ecological nutrient management (ENM) conceptual framework as it applies to organic farming systems and introduce linkages between plant function traits and soil elemental cycling processes that govern soil organic matter (SOM) transformations. ENM is an integrated approach to managing major biogeochemical cycles governing soil ecosystem services and SOM dynamics. When applied within organic farming systems, ENM integrates the use of cover cropping, intercropping, diversified rotation sequences, increased reliance on legumes, careful recycling of animal waste, and a variety of soil amendments with an eye toward recoupling biogeochemical cycles and the restoring ecological integrity of agroecosystems. I will discuss how plant biodiversity, soil microbial communities, and cross trophic interactions govern carbon, nitrogen, and phosphorus cycling and how organic management practices that focus on strategic use of plant diversity influence carbon accrual, plant acquisition of nitrogen and phosphorus, and retention of these nutrients in agroecosystems. I will consider processes occurring in the rhizosphere up to the field scale and review recent discoveries of mechanisms that regulate decomposition and SOM stabilization, including fast and slow cycling processes and interactions between newly added C and older, stabilized SOM reserves. For example, recent findings suggest that perennial legumes foster greater SOM stabilization and accrual as well as increased incorporation of nitrogen and phosphorus into SOM pools compared to annual legumes. Furthermore, the effects of plant species on ecosystem services valued by organic farmers can differ substantially even within plant genera and across ecotypes/cultivars of the same species. This interspecific and intraspecific variability in provision of ecosystem services suggests the need for a systematic approach to designing cropping systems that depend on biodiversity for the provision of complex ecosystem services related to SOM dynamics and soil function.
