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.

人类活动介导的氮（N）、磷（P）输入破坏了全球生物地球化学循环，然而微量营养元素与大量营养元素在塑造地表六足动物群落中的作用仍不明确。为厘清这一科学问题，我们在两处热带雨林开展了氮、磷及氮磷联合施肥实验，不仅评估了地表昆虫群落对大量营养元素添加的响应，同时探究了土壤自然微量营养元素有效性（钙（Ca）、钾（K）、镁（Mg）及钠（Na））的影响。研究结果表明，土壤中钙、镁、钠等微量营养元素的自然浓度与六足动物丰度显著相关，而钙、钾、镁则对操作分类单元（operational taxonomic unit，OTU）的丰富度存在显著影响。与之相反，施加氮和/或磷的实验施肥并未显著改变地表六足动物群落的结构与组成。此外，钙与钠成为调控群落组成的关键因子。本研究结果凸显了土壤微量营养元素在养分贫瘠热带雨林的地表栖息昆虫群落构建中的核心作用，这与氮、磷等大量营养元素的有限影响形成鲜明对比。