Over the past century, humans have profoundly altered global environmental conditions. Human appropriation of land and resources have reached an all-time high; temperatures have been warming by roughly 0.17˚ C per decade; precipitation patterns are shifting. A central focus of environmental science is to understand the impact of these changes on the functioning of biological communities. One of the most compelling bodies of evidence shows that global environmental changes are altering the onset of key life history events in organisms, such as timing of growth, maturation, and activity. However, most evidence of phenological shifts are derived from easily observed aboveground species, and there is very little evidence documenting phenological responses of soil communities to environmental change. Using an outdoor global change experimental facility, we quantified phenology of soil activity patterns in response to ten realistic future environmental scenarios. Treatments included a factorial combination of two climate regimes crossed with five land use scenarios: 1) conventional farming, (2) organic farming, (3) intensively used grassland maintained by frequent mowing, (4) extensively used grassland with moderate mowing and (5) extensively used grassland with moderate sheep grazing. We hypothesized that the temporal and spatial distribution of soil activity will be enhanced by warmer, wetter climates, as well as increases in plant species diversity, and plant biomass.
Results/Conclusions
We reveal hidden soil community activity stemming from a deeper and more even soil activity profile in extensively managed grasslands. In contrast, intensively managed grasslands promoted shallow activity profiles with most activity occurring in the 8 cm nearest to the soil surface. Longer duration of soil activity periods resulted from earlier onset and delayed decline of soil community activity that occurred in warmer wetter Spring and Fall, a response that was particularly pronounced in land use scenarios with deeper soil activity profiles, higher plant species richness, and more plant biomass. Although soil organisms often are assumed to turn on and off in response to cues from plants and climate, our results indicate that soil activity responses need not be synchronous across all soil depths. Environmental changes that promote evenness and diversity of soil activity profiles have the potential to modulate the influence of climate change on duration and magnitude of soil activity.