Diversity of soil organisms has key role in the carbon cycle.
Leipzig, Namur. Declines in the diversity and abundance of decomposers explain reductions in plant decay rates under the influence of chemical stressors, but not added nutrients. These are the new insights of a study published in the open access journal eLife. The global meta-analysis conducted by researchers at the German Centre for Integrative Biodiversity Research (iDiv), Leipzig University (UL) and the University of Namur in Belgium highlights the main anthropogenic effects on the biodiversity and functioning of ecosystems, and thus helps predicting the fate of different ecosystems around the world.
Plant litter decomposition is a major ecosystem function, linking plant biomass to carbon stocks in the soil and atmosphere, and releasing nutrients including nitrogen and phosphorus that influence soil biodiversity. Global change factors such as chemical stressors and nutrient additions can change the decomposition ability of soil species and thereby the plant decay rates. Previous experiments conducted in simplified conditions have shown that biodiversity loss has detrimental effects on ecosystem processes. However, how these results apply to real-world scenarios of change in biodiversity remains unclear.
Therefore, the three researchers at iDiv, UL and the University of Namur in Belgium set out to discover if the responses of plant litter decomposition to chemical stressors and added nutrients could be explained by changes in decomposer diversity across ecosystems.
69 studies analysed the effects of chemicals and added nutrients on decomposers
“Industrial and agricultural activities can have detrimental effects on decomposer organisms,” says first author Dr Léa Beaumelle, a postdoctoral researcher, who carried out the study at iDiv and UL but now works at the French National Research Institute for Agriculture, Food & Environment (INRAE). “They release chemical stressors such as metals and pesticides, as well as nutrients, into soil and water. These substances modify decomposer communities by affecting their diversity, abundance and metabolism,” says Beaumelle.
The team analysed the results of 69 independent studies that reported 660 observations of the effects of chemical stressors like pesticides or heavy metals or nutrient enrichment on animal and microbial decomposers and on plant litter decomposition. The researchers found that chemical stressors caused declines in the diversity and abundance of decomposers, which explained the reductions in plant decay rates. While this applied to chemical stressors in general, detrimental effects by nutrient only occurred at high levels of inputs. This suggests that when human activities decrease decomposer biodiversity, it can lead to significant effects on ecosystem functions, particularly so if inputs are high.
“Our findings could inform the design of suitable strategies to maintain biodiversity and ecosystem functioning,” concludes senior author Prof Nico Eisenhauer, Head of Experimental Interaction Ecology at the German Centre for Integrative Biodiversity Research (iDiv), Leipzig University. “But they also show that these strategies must take different human activities into account to improve the biodiversity and functioning of ecosystems.”
(scientists with iDiv affiliation and iDiv alumni bold)
Beaumelle, L., De Laender, F., Eisenhauer, N. (2020) Biodiversity mediates the effects of stressors but not nutrients on litter decomposition. eLife, DOI: 10.7554/eLife.55659