# Forest Management and the Colonization of Artificial Tree Holes by Aquatic Insect Larvae

## TL;DR

This study shows how forest management affects insect communities in artificial tree holes, highlighting the importance of less intensive practices to support biodiversity.

## Contribution

The study reveals species-specific colonization patterns and the impact of forest management on tree-hole insect communities.

## Key findings

- Forest management intensity and tree composition significantly influence insect abundance and community composition in artificial tree holes.
- Distance to natural microhabitats and microclimate changes negatively affect larval abundance.
- Protection and promotion of tree-related microhabitats can sustain tree-hole insect populations in managed forests.

## Abstract

Human activities in forests lead to alteration or even destruction of habitats for numerous organisms, often resulting in a decline of biodiversity. Insects inhabiting water‐filled tree holes may be especially sensitive to human impact as they require these microhabitats for at least part of their life cycle, with larvae mainly feeding on plant and animal debris accumulating in the water until they actively disperse in their adult stage. The processes leading to successful colonization of these microhabitats are not well understood, and it is unclear how forest management could influence them. We used sequential collection and recording of larval communities in artificial tree‐hole analogues to study the process of colonization by aquatic tree‐hole insects. We focused on the effects of parameters related to forest management as well as microhabitat properties on abundance, species richness, and community composition during colonization of artificial tree holes by aquatic tree‐hole insects. We observed complex, and partly species‐specific, temporal patterns of colonization of these new microhabitats. We found that the forest management intensity index ForMI, tree composition of forests as well as distance to natural water‐filled tree holes and debris type were important in shaping community composition of insect larvae inhabiting tree holes across the entire colonization process. Larval abundance was negatively affected by increased distance to natural microhabitats and by changes in microclimate. Our results suggest that forest management significantly impacts microhabitat colonization dynamics of tree‐hole insects, emphasizing the need for less‐intensively managed forests to support natural tree‐hole communities. We recommend the protection, creation, and maintenance of tree‐related microhabitats, for example, through the promotion of habitat trees in managed forests, to sustain higher abundances of tree‐hole inhabitants. Our findings underline the ecological value of water‐filled tree holes and support their integration into forest conservation strategies as both essential habitats and valuable indicators of environmental change.

The present study demonstrates the effects of forest management on insect communities during the colonization of artificial tree holes and reveals a dynamic, species‐specific pattern of colonization. It highlights the negative effects of forest management intensity and the dominant tree species of the forest stand on insect abundance and community composition, in addition to the influence of dispersal distances and physico‐chemical water parameters. The study underscores the role of suitable forest management practices in preserving water‐filled tree holes and supporting biodiversity in forests.