Plant diversity effects on soil food webs are stronger than those of elevated CO2 and N deposition in a long-term grassland experiment

Background/Question/Methods

Recent meta-analyses suggest biodiversity loss affects the functioning of ecosystems to a similar extent as other global environmental change agents. However, the structure and functioning of soil organisms have been hypothesized to be much less responsive to such changes, particularly to changes in plant diversity, than aboveground variables, though tests of this hypothesis are extremely rare. Here, we examined the responses of soil food webs (soil microorganisms, nematodes and microarthropods) to 13-year manipulation of multiple environmental factors that are changing at global scales, plant species richness, atmospheric CO₂and N deposition, in a grassland experiment in Minnesota, USA.

Results/Conclusions

Plant diversity was a strong driver of the structure and functioning of soil food webs, through several bottom-up (resource control) effects, while CO₂ and N only modestly impacted soil food webs. We found few interactions between plant diversity and CO₂ and N, likely because of weak interactive effects of those factors on resource availability (e.g., plant root biomass). Plant diversity effects likely were large because high plant diversity promoted the accumulation of soil organic matter in the site’s sandy, organic matter-poor soils. Plant diversity effects were not explained by the presence of certain plant functional groups. Our results underline the prime importance of plant diversity loss cascading to soil food webs (density and diversity of soil organisms) and functions. Since the present results suggest prevailing plant diversity effects and few interactions with other global change drivers, protecting plant diversity may be of high priority to maintain the biodiversity and functioning of soils in a changing world.