The long way back: Development of Central European mountain forests towards old-growth conditions after cessation of management

Questions Primary forests fulfil important roles in preserving biodiversity, storing carbon and increasing ecological understanding. Yet, they have become very rare in Europe. An important policy goal is thus to increase the share of naturally developing forests by creating protected areas in formerly managed forests. Here, we investigated: (a) if and how such forests return to conditions similar to old-growth; and (b) whether recently observed stand-replacing natural disturbances in combination with climate change set them onto an alternative developmental pathway. Location Durrenstein Wilderness Area (IUCN Cat. Ib) in the Austrian Alps, containing the Rothwald, one of the last primary forest remnants of Central Europe. Methods We built a chronosequence of 87 plots, spanning 220 years of forest development after the cessation of management, and compared them to old-growth forests. We analysed the recovery of nine attributes of forest composition, structure and functioning. To evaluate stand-level development of these attributes after recent natural disturbance and climate change, we additionally used a process-based simulation model. Results Old-growth forests showed a wide range of variability across investigated attributes. Forests converged to old-growth conditions after management ceased, with seven out of the nine attributes falling within the range of old-growth at the end of our chronosequence. The variation in tree diameters and the downed amount of deadwood were, however, still significantly lower than in old-growth forests after 220 years of unmanaged stand development. Simulations did not indicate an alternative developmental pathway of recently disturbed stands. Conclusions While a full return to old-growth conditions can take centuries, a number of important forest attributes recover quickly, indicating that protecting formerly managed forests is a valuable strategy to enrich forest landscapes. Our results indicate that the mountain forests of Central Europe have high ecological resilience, developing towards old-growth conditions after both past management and current natural disturbance.

Automated summary

The study in the Durrenstein Wilderness Area in the Austrian Alps shows that forests can gradually recover to conditions similar to old-growth forests after management cessation for 220 years, indicating high ecological resilience in Central European mountain forests. While a full return to old-growth conditions may take centuries, protecting formerly managed forests is a valuable strategy as important forest attributes can recover quickly.