# Invertebrate Communities and Driving Factors Across Woody Debris Types in Temperate Forests, Northern China

## TL;DR

This study explores how invertebrate communities change as woody debris decays in northern Chinese forests and how tree species and forest types influence these communities.

## Contribution

The study reveals systematic invertebrate succession patterns linked to wood decay stages and demonstrates the importance of tree species and mixed forests in sustaining biodiversity.

## Key findings

- Phytophagous invertebrates dominate early decay stages, while saprophagous and predatory groups thrive in later stages.
- Birch supports higher invertebrate abundance than larch due to lower wood density and richer nutrients.
- Mixed forests sustain more diverse invertebrate communities than pure forests by providing heterogeneous substrates.

## Abstract

In forest ecosystems, fallen trees (woody debris) function as important shelters rather than waste, providing food and shelter for diverse invertebrates. Our study demonstrates that invertebrate community composition undergoes systematic succession as wood decay progresses: phytophagous groups (e.g., cerambycid beetles) dominate initial decay stages while saprophagous (e.g., Diptera larvae) and predatory groups (e.g., centipedes) prevail in middle-to-late stages. Tree-species identity and forest type significantly influence invertebrate distribution. For instance, Betula platyphylla (birch) supports higher invertebrate abundance than Larix principis-rupprechtii (larch) due to its lower wood density and richer nutrient content. Mixed forests enhance this diversity by supplying heterogeneous woody debris substrates and creating complex microhabitats, thereby sustaining more intricate food webs compared to pure types. This study indicates that the conservation of fallen dead trees of various tree species and at different decay stages in forests are of great significance for maintaining soil biodiversity, promoting nutrient cycling, and enhancing the health and sustainability of forest ecosystems.

Woody debris decomposition is a key process in forest ecosystem material cycles, with invertebrate communities playing a vital role. Distinct physicochemical properties of woody debris types lead to varying effects on these communities. Taking woody debris in Saihanba’s Larix principis-rupprechtii plantations, Betula platyphylla natural secondary forests, and larch–birch mixed forests (northern China) as objects, we collected woody debris-inhabiting invertebrates via hand-sorting. We studied how tree species (larch/birch), forest types (pure/mixed), and decay stages (I–V) collectively regulate invertebrate community assembly. Results showed significant differences in woody debris physicochemical properties across these factors. Phytophagous groups dominated early decay stages (I–III) and decreased significantly (p < 0.05) with reduced wood density. In contrast, saprophagous and predatory groups increased with decay, correlated with higher TN and were more abundant in mixed than pure forests. NMDS indicated significant community differences among tree species/forest types in early decay, converging later. PLS-PM further confirmed functional groups’ response pathways to woody debris characteristics. Thus, preserving woody debris integrity and diversity in plantations is crucial for maintaining invertebrate diversity, promoting nutrient cycling, and enhancing forest ecosystem functions.