A Comparison of the Formation Rates and Composition of Tree-Related Microhabitats in Beech-Dominated Primeval Carpathian and Hyrcanian Forests

Abstract

Primeval forests in the temperate zone exist only as a few remnants, but theses serve as important reference areas for conservation. As key habitats, tree-related microhabitats (TreMs) are of intense interest to forest ecologists, but little is known about their natural composition and dynamics in different tree species. Beech forms a major part of the temperate forests that extend from Europe, home to European beech Fagus sylvatica L. (Fs), eastward to Iran, where Oriental beech Fagus orientalis Lipsky (Fo) is the dominant species. In this study, we compared TreMs in primeval forests of both species, using data from Fo growing in 25 inventory plots throughout the Hyrcanian forest belt in Iran and from Fs growing in a 9 ha permanent plot in the Uholka Forest of Ukraine. TreMs based on 47 types and 11 subgroups were recorded. Beech trees in the Hyrcanian forest had a higher mean diameter at breast height (dbh) than beech trees in Uholka and contained twice as many TreMs per hectare. Although the mean richness of TreMs per TreM bearing tree was similar in the two species, on the basis of the comparison single trees in two groups (n = 405 vs. 2251), the composition of the TreMs clearly differed, as the proportions of rot holes, root-buttress concavities, and crown deadwood were higher in the Hyrcanian Forest, and those of bark losses, exposed heartwood, and burrs and cankers higher in Uholka Forest. Estimates of TreMs dynamics based on dbh and using Weibull models showed a significantly faster cumulative increase of TreMs in Fo, in which saturation occurred already in trees with a dbh of 70–80 cm. By contrast, the increase in TreMs in Fs was continuous. In both species, the probability density was highest at a dbh of about 30 cm, but was twice as high in Fo. Because of limitations of our study design, the reason behind observed differences of TreM formation and composition between regions remains unclear, as it could be either result of the tree species or the environment, or their interaction. However, the observed differences were more likely the result of differences in the environment than in the two tree species. Nevertheless, our findings demonstrate that the Hyrcanian Forest, recently designated as a natural heritage site in Iran, is unique, not only as a tertiary relict or due to its endemic trees, herbs and arthropods, but also because of its TreMs, which form a distinct and rich habitat for associated taxa, including endemic saproxylic species.

Influence of Forest Management and Sylvicultural Treatments on Abundance of Snags and Tree Cavities in Mountain Mixed Beech Forests

“…Focusing on south-western European forests, Alberdi et al [17] found that the species composition of the stand has a strong influence on the amount of deadwood in mixed forests that showed double the volume of deadwood than that of pure conifer and broadleaf stands [17], confirming the findings of a previous study conducted in China [18]. On the other hand, little is known regarding the impact of different forest management systems on deadwood (in particular snags) volume and decay stage in Iranian forests where previous studies focused mostly on natural unmanaged forests [19,20].…”

The Use of Tree-Related Microhabitats as Forest Biodiversity Indicators and to Guide Integrated Forest Management

“…There are fewer studies on tree species such as Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) or Oriental beech (Fagus orientalis Lipsky (Fo)) from outside Europe [52][53][54][55][56]. All these studies have in common that tree species is a determining factor of TreM abundance and richness.…”

“…In this regard, diameter at breast height (DBH) has proven to be a strong and significant driver of TreM occurrence in all studies that considered this common mensurational variable [e.g., 15,34,39]. In general, large trees support a greater abundance and richness of TreMs across all tree species [51,52,57,58]. It is not fully understood whether tree species or dimension is more decisive, but both are usually the two most important drivers of TreM occurrence.…”

“…In addition, there is so far little information from oldgrowth or primary forests to facilitate comparisons with managed forests. However two studies have provided first reference numbers of TreMs for primary forests of European beech and Oriental beech [38,52].…”

“…The noise in these relationships is partially caused by the fact that forest-dwelling species included do not directly rely on any of the inventoried TreMs for their habitat requirements or the habitat range does not match the spatial scale at which TreMs have been inventoried. For example, some studies have ignored TreMs on dead wood [17,52]. This could have a significant impact on the result as not all species rely exclusively on TreMs borne by living trees and more TreMs occur on snags compared with living trees [57].…”