Legacy effects of nutrient addition reduces and displaces trophic niches in Collembola communities in a Brazilian woodland savanna

Ecosystems worldwide are being subjected to increasing rates of nutrient deposition. Additional nitrogen (N) and phosphorus (P) inputs and liming are common practices in agroecosystems that have long-term consequences for plant and microbial diversity and community structure during ecosystem restoration. However, legacy effects of nutrient deposition on multitrophic biodiversity and trophic interactions of soil organisms are poorly understood. Collembola is a good model group to study such effects. These small soil invertebrates are intimately linked to plants and microbes, and play an important role in soils by supporting soil fertility and energy channeling to higher trophic levels in soil food webs. Here, we studied the trophic niche structure of epigeic Collembola during a long-term (20 years) nutrient addition experiment in the Central Brazilian savanna (Cerrado), one of the tropical agricultural frontiers. We used descriptive isotopic metrics of Collembola communities based on stable isotopes of carbon and nitrogen to evaluate the legacy effects of fertilization (with N, P, and N + P additions) and liming on their trophic-niche structure. The strongest trophic niche shifts were observed under N addition, manifested in the form of (i) a reduction in trophic niche width-that is, decreased diversity of consumed basal resources available to the Collembola community-and (ii) in a more even distribution of Collembola taxa in trophic space. Community trophic niche was strongly displaced under P, N + P, and liming additions (i.e., it did not overlap with the control), reflecting intensified trophic links of Collembola to exotic C4 grasses. Overall, our results indicate that increased atmospheric N deposition simplifies the trophic structure of Collembola communities, which may affect the efficiency and pathways of energy channeling in soil food webs and soil functioning. In addition, the observed niche shifts suggests the need for flexibility in feeding by soil animals in savanna to persist under supplemental N + P and liming. Our study is among the first to explore the trophic structure of invertebrates in tropical soils and provides further evidence that nutrient deposition and agricultural fertilization and liming legacy effects have long-term consequences for soil organisms on multiple trophic levels.

Automated summary

Ecosystems worldwide are experiencing increasing rates of nutrient deposition, leading to long-term consequences for plant and microbial diversity and community structure. Research shows that increased atmospheric nitrogen deposition simplifies the trophic structure of Collembola communities, potentially impacting the efficiency and pathways of energy channeling in soil food webs.