Temporal Development of Microhabitats on Living Habitat Trees in Temperate European Forests

Tree-related microhabitats (TreMs) have been promoted as indicators of forest biodiversity and to guide conservation practices. Ensuring the provision of diverse TreMs in the long term is crucial for the survival of many forest-dwelling species. Yet, this task is challenging in the absence of information regarding TreM dynamics. We analysed the temporal development of TreMs on 11,569 living trees in temperate European forests. To identify drivers of change in TreM abundance and richness over a period of 3–12 years, we estimated the rates of TreM persistence and loss events at the tree-level using survival analysis methods: persistence was characterised by consistency and increment events (when TreM numbers were maintained or increased) and loss was defined as a reduction in TreM numbers or their disappearance. StratifiedCox proportional hazards models were fitted for different TreM groups. Our study revealed a highlydynamic TreM development on living habitat trees, particularly on large trees. While specific TreMs areprone to disappearing, irrespective of tree species or TreM groups, total TreM richness persists over a 12-year period. TreMs such as crown deadwood, epiphytes or woodpecker cavities are prone to decrease in thelong term. However, large trees were more likely to maintain a certain degree of TreM richness. Increasing diameters resulted in high persistence rates in seven TreM groups and concomitantly lowloss rates in four of them (exposed sap- and heartwood, concavities). Selecting habitat trees based on TreMs should consider the likelihood of TreMs being lost over time, to ensure the long-term provision of microhabitats for associated species.