The effect of forest structure on the occurrence of tree-related microhabitats in primary mountain forests of Bulgaria

Polona Zakrajšek

Master's thesis

Abstract:

Tree-related microhabitats (TreMs) are becoming widely acknowledged as crucial substrates and structures for biodiversity. They serve as an indirect biodiversity indicator for species that use them as habitat or substrate for at least a part of their life cycle, highlighting their importance for ecological monitoring. Primary forests provide key ecosystem functions and serve as a baseline for studies of ecological processes. Even though they represent a small fraction of European forests, they still continue to disappear. This thesis focuses on the relationship between features of forest structure and their effects on the occurrence, abundance, and diversity of TreMs. Data collection was conducted in Bulgaria, in the primary mountain beech forests in the Central Balkan mountain range with the REMOTE Primary Forests project. A total of 42 permanent monitoring plots across three stands, dominated by European beech (Fagus sylvatica), were surveyed in September 2022, and TreMs were recorded using standardised hierarchical methodology. Generalised linear mixed models were used to test the effect of tree characteristics on the occurrence of TreMs on the tree level and the abundance and diversity of TreMs on the plot level. Diameter at breast height (DBH) and tree status significantly correlated with the occurrence of TreMs on the tree level. On the plot level, basal area, the density of trees, and altitude significantly increased the overall TreM abundance. In comparison, the density of trees and the density of large dead trees significantly increased the diversity of TreM types. An average abundance of 684.4 TreMs per ha is observed across stands, 532.2 TreMs per ha by live trees and 152.2 TreMs per ha by snags. While snags represent only 11% of all trees, they are not only more likely to host TreMs but also account for almost one third of all TreMs’ total abundance. Our findings underline the importance of large trees and snags in contributing to the overall TreM abundance and diversity.

Keywords

biodiversity indicators, habitat trees, primary forests, tree-related microhabitats, forest structure

Language used: English

Date on which the thesis was submitted / produced: 7. 4. 2024

Thesis defence

• Supervisor: Ing. Daniel Kozák, Ph.D.
• Reader: Andreea Spînu, externi

Czech University of Life Sciences Prague

Faculty of Forestry and Wood Sciences

Master programme:
Forestry, Water and Landscape Management