Effects of manipulated soil microclimate on mesofaunal biomass and diversity

In experimentally heated plots, each spanning a microclimate and vegetation gradient within a subalpine meadow, heating enhanced both soil mesofaunal biomass and diversity in a cool, wet summer. In a warmer, drier summer, in contrast, heating depressed diversity and biomass in the drier zone of the plots and diversity in the moist zone, but enhanced biomass in the moist zone. Biomass and diversity were positively correlated across plots and, under conditions of moisture stress, both positively correlated with soil organic matter. Data from closed cores indicate that the effects of heating on mesofauna were due to in-plot effects of heating rather than to heating-induced movement of soil organisms. The sensitive response of soil mesofauna to altered microclimate and the dependence of that response on a variety of environmental factors suggest both promise and limitations in using either experimental manipulations or natural correlations between soil microclimate and mesofaunal populations to forecast effects of climate change.