Agricultural intensification has been shown to reduce soil biodiversity and associated ecosystem services. Most studies have shown the effects of intensification on soil biota at field or local scales. However, the functional significance of biodiversity may only appear at larger spatial and temporal scales, when spatial exchanges occur among local systems throughout a landscape. As a result, landscape studies are needed to evaluate patterns of biodiversity. Two recent studies address this issue for soil food web biodiversity over different landscape types. A study from north central Kansas examined soil food webs in harvested perennial grasslands and adjacent annual croplands over five counties. The second study was conducted in the Central Valley of California to explore relationships of above and belowground biodiversity over a landscape gradient of agricultural intensification.
Results/Conclusions
Results from the Kansas study show major differences in bacterial community abundance and structure. Nematode community indices suggested enhanced fungal decomposition pathways, fewer plant-feeding nematodes, and greater food web complexity and stability in grassland soils than in annual cropland soils. Results from the California study show systematic patterns of soil biodiversity decline related to agricultural intensification. Agricultural soils supported less structured soil food webs and lower diversity than upland grassland sites. Both studies incorporated a wide array of soils and environmental conditions, indicating that the observed trends transcended site-specific conditions. The enhanced biodiversity and food web complexity observed in both studies was associated with indicators of higher soil quality and thus, greater regulating ecosystem services.
