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B5) Bats and Forest Structure

Landscape-moderated use of forest structures by bats

Veronika Braunisch 1,2 & Ilse Storch 3
Doctoral researchers: Marlotte Jonker 1,3 (since 2016) & Anna-Lena Hendel 3 (since 2019)

1 Forest Research Institute of Baden-Württemberg (FVA), Department of Forest Conservation

2 University of Bern, Faculty of Science, Department of Biology, Institute of Ecology & Evolution,
   Division of Conservation Biology

3 University of Freiburg, Faculty of Environment & Natural Resources, Institute of Forest Sciences,
   Chair of Wildlife Ecology and Management


Bats are considered to be indicators of forest structural complexity and are frequently selected as target species for conservation programs integrating key structural elements in forest management. Forest-dwelling bat species use old and dead trees as roosting sites and forest gaps and linear elements for foraging and commuting. Retention of old-growth structures may be beneficial, yet, as recent studies indicate, their use and usability by bats may strongly depend on the landscape context.

The first doctoral researcher, Marlotte Jonker, focuses on how retention elements across the landscape influence the occurrence and abundance of bat species inside forest. Shedding light on the underlying mechanisms behind those associations, the PhD project of Anna-Lena Hendel now investigates how quantity and distribution of forest structures affect bats by mediating the food resource availability and further the connectivity between resources that bats need.

Finally, in the third phase of the project, B5 aims to address the effectiveness of the forest structural retention measures relative to other instruments of forest biodiversity conservation by comparing the ConFoBi data with data collected at large, segregative restoration sides (i.e. strictly protected areas). Additionally, the frequency and timeframe at which important structures develop after management cessation will be explored. The results will finally be synthesized to provide conservation recommendations that aim at the provisioning of continuous habitat for different bat species at the landscape scale.


Research questions and hypotheses

B5 relates bat diversity, activity, and type of use to forest characteristics at the local and landscape level, expecting:

(1) Effects on species presence, activity and diversity:

  • The activity and diversity of forest-specialists will increase with the abundance of habitat trees, dead wood and associated microhabitats at the plot level.
  • The species-specific use of these structural elements at the local scale will be modulated by their abundance in the surrounding landscape.
  • The diversity of bat species and guilds will increase with structural heterogeneity at both the forest-stand and landscape scale.

(2) Effects on ecological functions:

  • Habitat connectivity, especially connecting elements such as gaps and linear structures in the forest landscape, explain local-scale variance in bat activity.
  • Food abundance and foraging activity of bats is related to local forest structure, but foraging activity will be modulated by matrix permeability and connecting structures at the landscape scale.

(3) Differences in the effectiveness of retention forestry compared to other (integrative and segregative) forest biodiversity instruments, with the relative effectiveness depending on the species traits, its habitat requirements and the density and connectivity of retention sites.



Approach, methods, and linkages

Automated acoustic recorders were deployed to detect bat species(-groups) and to quantify their activity. Species presence, richness, diversity, and activity are then related to forest structure and landscape conditions, assessed by remote sensing and plot-scale terrestrial mapping.

LiDAR-information capturing the 3D-characteristics of sub-canopy space (A1) and forest structure mapping (A2, C1) will be used to predict bat occurrence at the stand scale. Landscape-scale variables, generated from GIS-databases and stereo-aerial photographs, provide information about the area-wide distribution of structural elements, such as gaps and standing deadwood.

The assessment of food availability (collaboration with B6) and the distribution of connecting structures such as edges within the forest that we hypothesize to be important for bats to commute between critical resources will allow for elucidating functional relationships. By relating bat presence and diversity to structural characteristics at multiple spatial scales, quantitative target values for integrative forest management will be derived.



During the first two years, bats were repeatedly recorded at all 135 ConFoBi plots and species abundance and diversity-related habitat structure were measured at plot and landscape level. The ongoing analyses show the importance of tree-related microhabitats (Basile et al., 2020) as well as of deadwood and canopy openings at the plot level for bat activity and richness (Augustynczik et al. 2012). The latter structures are now further elucidated for their connecting function.

In addition, in a pilot phase, light traps were employed on a subset of plots to sample moth and other nocturnal invertebrates to link food abundance to forest structures. Further data is currently being collected to link food supply with foraging activity in order to understand the indirect effects of forest structures on the habitat functionality of bats. Thereby the observed nightly activity patterns and recorded feeding buzzes by foraging bats will be used to establish and validate these relationships.


Future projects

Next PhD project (starting 1 July 2022)

In the third phase, data sampled on the ConFoBi plots (i.e. representing different levels of retention) will be compared with data from an associated project at the Forest Research Institute of Baden- Wuerttemberg (FVA), in which similar data have been collected at the extremes of the management gradient (i.e. unmanaged forests and experimental clearcuts).

In particular, the third PhD3 project will

  • evaluate the relative efficiency of small integrative (i.e. retention sites) versus large segregative restoration sites (i.e. strictly protected areas), considering effects of patch size, patch number, spatial configuration and connectivity on target organisms
  • address the time scale and frequency at which the desired structures develop: under “passive” restoration processes in contrast active creation of structures.


Based on these results, B5 aims to provide forest managers with quantitative target values for the abundance and configuration of stand-scale and landscape-scale structural habitat elements for bats and compare the potential of different management regimes to provide these elements.

Skills required for PhD3 applicants in B5:

In addition to the general requirements described in the job advertisement, we seek a researcher with strong conceptual and analytical skills and a good knowledge of the European bat fauna, preferably with experience in the acoustic identification of bats. As the data will have to be analysed in a semi-automatic manner, experience in using bioacoustic software tools for bat calls (e.g. BatScope, BatExplorer, Kaleidoscope etc.) is an advantage. Additionally, the candidate should have a strong background in statistics and ecological modelling, good knowledge in R and GIS programmes (ArcGIS or QGIS) and an experience in handling large datasets.


ConFoBi-publications with B5

Asbeck, Thomas; Sabatini, Francesco; Augustynczik, Andrey L. D.; Basile, Marco; Helbach, Jan & Jonker, Marlotte et al. (2021). Biodiversity response to forest management intensity, carbon stocks and net primary production in temperate montane forests. Scientific reports, 11, 1625.

Augustynczik, Andrey L. D.; Asbeck, Thomas; Basile, Marco; Jonker, Marlotte; Knuff, Anna & Yousefpour, Rasoul et al. (2020). Reconciling forest profitability and biodiversity conservation under disturbance risk: the role of forest management and salvage logging. Environ. Res. Lett., 15, 0940a3.

Basile, Marco; Asbeck, Thomas; Jonker Marlotte; Knuff, Anna K.; Bauhus, Jürgen & Braunisch, Veronika et al. (2020). What do tree-related microhabitats tell us about the abundance of forest-dwelling bats, birds, and insects? Journal of environmental management, 264, 110401.

Gossner, Martin M.; Gazzea, Elena; Diedus, Valeriia; Jonker, Marlotte & Yaemchuk, Mykola (2020). Using sentinel prey to assess predation pressure from terrestrial predators in water-filled tree holes. Eur. J. Entomol., 117, 226–234.

Gustafsson, Lena; Bauhus, Jürgen; Asbeck, Thomas; Augustynczik, Andrey Lessa Derci; Basile, Marco & Frey, Julian et al. (2020). Retention as an integrated biodiversity conservation approach for continuous-cover forestry in Europe. Ambio, 49, 85–97.

Kirsch, Jennifer-Justine; Sermon, Jana; Jonker, Marlotte; Asbeck, Thomas; Gossner, Martin M. & Petermann, Jana S. et al. (2021). The use of water-filled tree holes by vertebrates in temperate forests. Wildlife Biology, 2021.

Storch, Ilse; Penner, Johannes; Asbeck, Thomas; Basile, Marco; Bauhus, Jürgen & Braunisch, Veronika et al. (2020). Evaluating the effectiveness of retention forestry to enhance biodiversity in production forests of Central Europe using an interdisciplinary, multi-scale approach. Ecology and evolution, 10, 1489–1509.