Value of old forest attributes related to cryptogam species richness in temperate forests: A quantitative assessment

摘要

Changes in temperate forest ecosystems resulting from a long history of forest exploitation may severely impact current cryptogam diversity. We documented the distribution of cryptogams in representative forest types between 200 and 1000 m a.s.l. in central Europe, in managed and unmanaged stands. This survey included one-time inventories of lichens and bryophytes, 2 years of regular monitoring of macrofungi, and a detailed description of forest structure (live trees and dead woody debris) in 96 sampling plots (2500 m(2) each) in six study areas in the Czech Republic. On this basis, we attempted to identify the quantitative limits of forest structural attributes that affect cryptogam diversity along a gradient of forest management practices in central Europe. In total, we recorded 1387, 173 and 103 species of macrofungi, lichens and bryophytes, respectively, of which 149,99 and 4 were red-listed species. Species richness was correlated among observed taxa at the plot scale, and rare and red-listed species made higher contributions in species-rich communities. Cryptogam species richness showed both common and taxa-specific patterns in relation to forest structure, tree species composition, age of the oldest tree strata and elevation. We found a positive influence of the largest-diameter tree classes (stem diameter >80 cm) on the species richness of all cryptogam taxa, whereas the contribution of dead wood to the fit of a linear mixed effect model was minimal. Nevertheless, the magnitude of total and red-listed species richness was remarkably high in plots in which at least one large tree or woody object occurred compared to plots lacking these attributes. The effect of large dead wood debris (diameter >80 cm and unit volume >1 m(3)) was not replaced by total dead wood volume, even though it was relatively high (>40 m(3) ha(-1)). Hence, both large live trees and woody debris compartments are probably important for the species richness of cryptogam communities. However, the spatial pattern of cryptogam communities at a given time point (i.e., the time of our survey) was associated with the spatial and temporal heterogeneity of live tree structures, but less with that of dead wood substrates. Large tree and woody debris characterize forests that have been unmanaged for at least several decades and occasionally occur in the oldest of moderately managed forests. The importance of these cryptogam refuges in managed forests should not be underestimated because their continuing disappearance will probably result in the impoverishment of cryptogam richness at regional scales. (C) 2015 Elsevier Ltd. All rights reserved.