Fertilization superimposes the legume effect on microbial efficiency in a grassland plant diversity gradient

Background/Question/Methods

The extreme loss of biodiversity and elevated N deposition are two of the most crucial anthropogenic factors driving ecosystem change. Although both received considerable attention in previous studies, information on their interactions and consequences of these interactions for ecosystems is scarce. In particular, little is known about how soil biota and their functions are affected by combined changes in biodiversity and N deposition. We investigated both the consequences of plant diversity loss and elevated N deposition for the performance and functioning of soil microbial communities on a local scale in the framework of a long-term study in semi-natural grassland (Jena Experiment).

Results/Conclusions

The results suggest that N addition significantly increased microbial C use efficiency, but did not alter microbial biomass. Legumes influenced microbial biomass and C use efficiency in the same way but legume impacts were superimposed by fertilization. In contrast, plant species richness enhanced microbial respiration and biomass but did not affect microbial C use efficiency. Our results highlight the role of plant diversity loss and N deposition as well as interactions between plant community composition and N deposition for microbial performance and functioning. Considering the multiple side effects of fertilization, promoting plant diversity and legume presence might be crucial factors improving the functioning of managed grasslands.