What do tree-related microhabitats tell us about the abundance of forest-dwelling bats, birds, and insects?

Marco Basile; Thomas Asbeck; Marlotte Jonker; Anna K Knuff; Jürgen Bauhus; Veronika Braunisch; Grzegorz Mikusiński; Ilse Storch

doi:10.1016/j.jenvman.2020.110401

What do tree-related microhabitats tell us about the abundance of forest-dwelling bats, birds, and insects?

J Environ Manage. 2020 Jun 15:264:110401. doi: 10.1016/j.jenvman.2020.110401. Epub 2020 Mar 26.

Authors

Marco Basile¹, Thomas Asbeck², Marlotte Jonker³, Anna K Knuff⁴, Jürgen Bauhus², Veronika Braunisch⁵, Grzegorz Mikusiński⁶, Ilse Storch⁷

Affiliations

¹ Chair of Wildlife Ecology and Management, University of Freiburg, Tennenbacher Str. 4, D-79106, Freiburg, Germany. Electronic address: marcob.nat@gmail.com.
² Chair of Silviculture, Institute of Forest Sciences, University of Freiburg, Tennenbacher Str. 4, D-79106, Freiburg, Germany.
³ Chair of Wildlife Ecology and Management, University of Freiburg, Tennenbacher Str. 4, D-79106, Freiburg, Germany; Forest Research Institute of Baden-Württemberg (FVA), Wonnhaldestr. 4, D-79100, Freiburg, Germany.
⁴ Chair of Nature Conservation and Landscape Ecology, University of Freiburg, Tennenbacher Str. 4, D-79106, Freiburg, Germany.
⁵ Forest Research Institute of Baden-Württemberg (FVA), Wonnhaldestr. 4, D-79100, Freiburg, Germany; Conservation Biology, Institute of Ecology and Evolution, University of Bern, Baltzerstr. 6, CH-3012, Bern, Switzerland.
⁶ Chair of Wildlife Ecology and Management, University of Freiburg, Tennenbacher Str. 4, D-79106, Freiburg, Germany; Department of Ecology, Swedish University of Agricultural Sciences SLU, Grimsö Wildlife Research Station, SE 730 91, Riddarhyttan, Sweden.
⁷ Chair of Wildlife Ecology and Management, University of Freiburg, Tennenbacher Str. 4, D-79106, Freiburg, Germany.

PMID: 32217309
DOI: 10.1016/j.jenvman.2020.110401

Abstract

Retaining trees during harvesting to conserve biodiversity is becoming increasingly common in forestry. To assess, select and monitor these habitat trees, ecologists and practitioners often use Tree-related Microhabitats (TreMs), which are assumed to represent the abundance and diversity of environmental resources for a wide range of forest-dwelling taxa. However, the relationship between TreMs and forest organisms is not fully understood. In this context, we attempted to identify and quantify the links between TreMs and three groups of forest organisms: insects, bats, and birds. Specifically, we tested whether species abundance is influenced by TreM abundance, either as direct predictor or as mediator of environmental predictors. We collected data in 86 temperate, 1-ha mixed forest plots and employed a hierarchical generalized mixed model to assess the influence of seven environmental predictors (aspect, number and height of standing dead trees, cover of herb and shrub layer, volume of lying deadwood, and terrain ruggedness index (TRI)) on the abundance of TreMs (15 groups) on potential habitat trees, insects (10 orders), bats (5 acoustic groups) and birds (29 species) as a function of seven environmental predictors: aspect, number and height of standing dead trees, cover of herb and shrub layer, volume of lying deadwood, and terrain ruggedness index (TRI). This allowed us to generate a correlation matrix with potential links between abundances of TreMs and co-occurring forest organisms. These correlations and the environmental predictors were tested in a structural equation model (SEM) to disentangle and quantify the effects of the environment from direct effects of TreMs on forest organisms. Four TreM groups showed correlations > |0.30| with forest organisms, in particular with insects and bats. Rot holes and concavities were directly linked with three insect groups and two bat groups. Their effect was smaller than effects of environmental predictors, except for the pairs "rot holes - Sternorrhyncha" and "rot holes - bats" of the Pipistrellus group. In addition, TreMs had indirect effects on forest organisms through mediating the effects of environmental predictors. We found significant associations between two out of fifteen TreM groups and five out of 44 forest organism groups. These results indicate that TreM abundance on potential habitat trees is not suited as a general indicator of the species abundance across broad taxonomic groups but possibly for specific target groups with proven links.

Keywords: Biodiversity indicator; Forest management; Retention forestry; Structural equation models; TreMs.

MeSH terms

Animals
Biodiversity
Birds*
Ecosystem
Forestry
Insecta
Trees*