Saproxylic Species Richness Research Articles

Coverage based diversity estimates of facultative saproxylic species highlight the importance of deadwood for biodiversity

How many species can live in a specific habitat is a key question in conservation biology. Due to its heterogeneity, deadwood supports highly diverse communities. The total number of species related to deadwood is, however, underestimated by most empirical community studies. First, as most reports on saproxylic species richness do not relate the number of species observed to the sample size used, it is not possible to draw conclusions about the representativeness of the species richness observed. Secondly, the assessment of species richness is usually limited to obligate saproxylic species, i.e., species classified by experts as being strictly dependent on deadwood. Hence, many species are ignored that can be considered facultative saproxylic; i.e., they are not dependent on deadwood but clearly benefit from it. The present study aims to statistically estimate the proportion of obligate and facultative saproxylic species among Coleoptera, Arachnida and Heteroptera in a European mountain forest. Therefore, we applied rarefaction/extrapolation based on sample coverage estimators, using data from an experimental approach including three trapping methods. The estimates suggest that obligate and facultative saproxylic beetles account for 28% and 19% of the total species richness of beetles, respectively. The estimated proportion of obligate saproxylic Heteroptera and Arachnida species was 4% and 12%. Facultative saproxylics were estimated to account for 24% and 69% of the total species richness, respectively. In summary, our study shows that the share of arthropod diversity related to deadwood is about 50 to 70%, within the three taxa Coleoptera, Arachnida and Heteroptera in a temperate forests temperate mountain forest, which is higher than previously assumed. This highlights the importance of deadwood for forest biodiversity and further supports deadwood restoration activities.

Quality of substrate and forest structure determine macrofungal richness along a gradient of management intensity in beech forests

The richness of saproxylic species is commonly found to be compromised in managed forests. However, it is often less clear if this reflects local scarcity of high quality deadwood objects or changes to the overall forest structure. Further, anthropogenic and natural drivers working at the landscape scale may have a strong impact. Hence, it is difficult to give detailed advice on how to conserve biodiversity in a cost-effective manner. Here we explored macrofungal richness on deadwood across a gradient of forest management intensity in Danish Fagus sylvatica forests. We aimed to disentangle the importance of habitat quality per se from the effects of variables recorded at the forest stand and landscape scales. Data was collected from 40 beech stands, each representing one of four broad management types: conventionally managed, near-to-nature managed, recently unmanaged and long unmanaged. Stands were aggregated within six larger forest clusters, to account for variation at the landscape scale. Fungal species were recorded as fruitbodies on deadwood at five decay stages. We found that the four management types showed strong differences in fungal richness, deadwood volume and forest structure, with long unmanaged stands having notably higher structural complexity and species richness. Fungal species richness and presence of red-listed fungi appeared to be mainly driven by deadwood volume, tree species and decay stage, but some stand-level variables such as canopy gaps, basal area and stand age were also of importance. Lying coarse deadwood had the highest species richness while standing coarse woody debris and fine deadwood had lower species density. Saproxylic fungal richness on individual deadwood objects was largely affected by resource quality and size, which is often limited in managed forests. Our results indicate that the best measure to increase fungal species richness, especially in managed stands, is to increase the amount of large diameter deadwood.