Effects of altered soil-water availability on a tallgrass prairie nematodecommunity

Climate change predictions for the Great Plains region of North America inc lude reduced growing season precipitation. The consequence of this predicti on for soil fauna and belowground processes was investigated at two spatial scales by integrating experimental manipulation of soil moisture levels wi th natural variation in soil-water availability. Experiments consisted of ( 1) reciprocal core transplants across a regional precipitation gradient and (2) supplemental irrigation applied across a local topographic gradient. T his report examines functional-level responses by the tallgrass prairie nem atode community to differences in soil moisture levels over a four-year per iod. Effects on nematode community structure were complex and dependent upo n nematode trophic habit and depth in the soil profile. The strongest and m ost consistent responses to changes in soil-water availability were display ed by herbivorous taxa, with 71% higher densities observed under wetter soi l conditions across experiments and years. Responses of microbial-feeding n ematodes were more variable, with lower densities observed, in some cases, in the presence of experimentally-increased soil moisture levels. Effects o f regional differences in soil-water availability on the nematode community were uniformly restricted to depths >20 cm. Community responses to short-t erm changes in soil moisture were not consistent with patterns in community structure developed under different natural moisture regimes, suggesting d ivergent short-term and long-term responses of belowground biota and proces ses to changes in soil-water availability. (C) 1999 Elsevier Science B.V. A ll rights reserved.