The vast majority of biodiversity on Earth lives in the soil; to what degree are this diversity and the ecosystem functions they perform regulated by climate and plant productivity? In this study, we seek to determine the relationship between climate/Net Primary Productivity (NPP) and soil food web structure. Research sites, each consisting of a forest and paired grassland, are located along east-west transects in Oregon; these transects encompass climates producing the greatest productivity and nearly the least productivity on the continent. Samples will be taken from each site once per season.

The forested sites are characterized primarily by a fungally-based food web and soils with a deep humus layer. The paired grassland sites support a primarily bacterially-based food web with minimal organic soil layers.

Though annual litterfall adds labile nutrients, much of the actual food web is controlled by the rate and periodicity of litter-shredding by millipedes and isopods – which takes place at different seasons along the transects. Thus energy and nutrients are made available at different times of year in the different systems. By monitoring the seasonal changes in food web structure along this gradient, we can capture a more complete picture of the dynamics of each system. The ultimate goal of this research is to produce a quantitative, predictive model relating climatic parameters, nutrient input, food web structure, and decomposition rate.