Soil invertebrates facilitate plant nitrogen assimilation in a tropical seasonal secondary forest

Abstract

Nitrogen (N) is an essential nutrient for plant growth, and its availability frequently constrains primary productivity during forest recovery 1. Soil invertebrates play a crucial role in N mineralization during litter decomposition 2; however, whether they regulate downstream plant N assimilation remains unclear. To address this knowledge gap, we carried out a 15-month invertebrate exclusion experiment in a tropical seasonal secondary forest, using N-stable-isotope (15 N) tracers to track N transfer from 15 N-labeled-leaf litter to plant leaves in the presence or absence of soil invertebrates. We found invertebrates increased 15 N atom excess in plant leaves by 59.4% by enhancing 15 N release from 15 N-labeled-leaf litter by 6.3%. This study provides direct evidence that soil invertebrates represent an underappreciated pathway linking biodiversity, primary productivity, and nutrient cycling. As active regulators of plant nutrition and N turnover, soil invertebrates are crucial for plant growth and carbon sequestration 1, especially in secondary forests that are increasingly becoming the predominant forest type in tropical regions 3.