Predictors of Microhabitat Frequency and Diversity in Mixed Mountain Forests in South-Western Germany

Josef Großmann,Jürgen Bauhus,Patrick Pyttel,Juliane Schultze

doi:10.3390/f9030104

Josef Großmann, Jürgen Bauhus + Show 2 more

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https://doi.org/10.3390/f9030104

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Abstract

Tree-related microhabitats are an important determinant of forest biodiversity. Habitat trees, which typically provide many microhabitats such as hollows, crown dead wood, etc., are therefore selected to maintain those structural attributes within managed forests. To what extent the occurrence of microhabitats on potential habitat trees may be predicted from common tree attributes is a question of high practical relevance. Until now, most studies have attempted to predict the quantity of microhabitats at the tree or forest stand level. In our study, we aimed at explaining microhabitat occurrence from a qualitative perspective by considering their diversity. Tree diameter at breast height (dbh), tree species, and canopy class were useful predictors of microhabitat diversity. Microhabitat diversity on broadleaved trees was on average higher than in conifers of the same diameter. In contrast to microhabitat quantity, microhabitat diversity saturated towards higher dbh levels. Microhabitat diversity in beech trees of lower tree canopy classes was found to be surprisingly high. Habitat trees support not only more, but also more diverse, microhabitats in comparison to crop trees. Considering these findings on microhabitat distribution, the selection of habitat trees within Central European mixed mountain forests can be significantly improved.

Highlights

The structural and biological diversity of central European forests have been altered by human activities over time [1,2]
Dominating forest types are mixed mountain forests composed of European beech (Fagus sylvatica L.; on beech), silver fir (Abies alba Mill.; on fir), Norway spruce
The occurrence of microhabitat categories differed between habitat trees and crop trees (Figure 1)

Summary

Introduction

The structural and biological diversity of central European forests have been altered by human activities over time [1,2]. Old-growth structures provide habitats and niches that are required by a large number of forest dwelling species [7]. To compensate for the lack of old-growth forests in the landscape and to maintain old-growth dependent species in managed forests, the frequency of habitats typical for late successional phases can be substantially increased through forest management [10]. This can be realized, for example, by the retention of dead wood and habitat trees [10,11]. The retention of habitat trees is a key element in forestnature conservation concepts in many European countries [12]

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