Micronutrients drive ground hexapod communities in tropical forests: insights from N and P fertilization experiments

Human-induced inputs of nitrogen (N) and phosphorus (P) disrupt global biogeochemical cycles, yet the role of micronutrients versus macronutrients in shaping ground hexapod communities remains unclear. To address this, we conducted an N, P, and NP fertilization experiment in two tropical rainforests, evaluating the response of ground insect communities to macronutrient additions but also to natural soil micronutrient availability (calcium (Ca), potassium (K), magnesium (Mg) and sodium (Na)). Our findings revealed that natural concentrations of soil micronutrient such as Ca, Mg, and Na were strongly correlated with hexapod abundance, while Ca, K, and Mg influenced operational taxonomic unit (OTU) richness. Conversely, experimental fertilization with N and/or P did not significantly alter ground hexapod community structure or composition. Furthermore, Ca and Na emerged as critical factors in shaping community composition. These results underscore the pivotal role of soil micronutrients in structuring ground-dwelling insect communities in nutrient-poor tropical forests, contrasting with the limited influence of macronutrients like N and P.