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Beetle diversity is higher in sunny forests due to higher microclimatic heterogeneity in deadwood

Abstract

Microclimate is a crucial driver of saproxylic beetle assemblages, with more species often found in sunny forests than in shady ones. Whether this pattern is caused by a higher detectability due to increased beetle activity under sunny conditions or a greater diversity of beetles emerging from sun-exposed deadwood remains unclear. This study examined whether sun exposure leads to higher microclimatic heterogeneity in deadwood and whether this drives beetle diversity in deadwood logs and at forest stand scale. Saproxylic beetles were sampled at the stand scale using flight-interception traps and at object scale using stem-emergence traps on deadwood logs at the same site. The variability in wood surface temperature was measured on single logs and between logs as a proxy for microclimatic heterogeneity in deadwood. Abundance in sunny forests was higher at the stand scale, and in shady forests at the object scale. The estimated number of species was higher in sunny forests at both scales and correlated positively with temperature variability on single logs and between logs at the stand scale and, albeit weakly, with temperature variability on single logs at the object scale. Gamma-diversity, and thus beta-diversity, across logs at the object scale was higher in sunny forests. These findings indicate that sun exposure promotes saproxylic beetle diversity due to higher microclimatic heterogeneity within and between deadwood logs. Our study therefore corroborates previous research demonstrating the importance of canopy cover and microclimate for forest biodiversity.

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Acknowledgements

We thank the administration of the Bavarian Forest National Park. Special thanks to Willi Hoff for supporting this project for several years. We also thank Boris Büche and Alexander Szallies for identifying beetles to the species level, and all helpers in the field and laboratory.

Funding

This research was supported by the project ‘BioHolz’ (Grant no. 01LC1323A) in the funding program “Research for the Implementation of the National Biodiversity Strategy (F&U NBS)” of the German Federal Ministry for Education and Research (BMBF) and the German Federal Agency for Nature Conservation (BfN), with funds provided by the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU).

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Authors

Contributions

SS, JH, and LL developed the idea of the manuscript. RB, CB, and JM designed the experiment. LL, SS, and JH collected the data. LL and JH analyzed the data. LL, SS, and JH led the writing of the manuscript. All authors have contributed critically to the drafts and gave final approval for publication of the submitted manuscript.

Corresponding author

Correspondence to Ludwig Lettenmaier.

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Conflict of interest

The authors have no conflicts of interest to declare.

Additional information

Communicated by Joel Trexler .

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Supplementary file1 (DOCX 1083 kb)

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Lettenmaier, L., Seibold, S., Bässler, C. et al. Beetle diversity is higher in sunny forests due to higher microclimatic heterogeneity in deadwood. Oecologia 198, 825–834 (2022). https://doi.org/10.1007/s00442-022-05141-8

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  • DOI: https://doi.org/10.1007/s00442-022-05141-8

Keywords

  • Deadwood
  • Emergence trap
  • Experiment
  • Habitat heterogeneity
  • Microclimate