Structural changes in a primeval beech forest at the landscape scale

Quantitative estimates of change of primeval European beech (Fagus sylvatica L.) forests at the landscape scale over time are scarce due to both the few remnants of such forests and the absence of repeated sample plot inventories. This forest ecosystem is thought to be relatively stable over time, but it remains unclear what drivers contribute to this stability. Here, we studied temporal change in one of the largest primeval beech forests. Our analysis is based on two consecutive inventories on 238 permanent sample plots in the Uholka-Shyrokyi Luh forest in Transcarpathia, Ukraine, covering 102.8 km(2). The inventories were carried out in 2010 and 2019. This data allowed us to derive quantitative estimates for the main structural characteristics tree density, basal area and volume on a landscape scale and to characterize the demographic processes that shape this forest ecosystem. The structural characteristics tree density (2010: 441 N ha(1), 2019: 458 N ha(-1)), basal area (2010: 35.9 m(2) ha(-1) , 2019: 35.4 m(2) ha(-1)), and standing volume (2010: 578 m(3) ha(-1), 2019: 584 m(3) ha(-1)) of the living trees remained stable between the two inventories. The species composition, characterized by a pronounced dominance of beech, remained virtually unchanged as well, with 97.9% of the stems being beech trees in the first and 97.1% in the second inventory. In contrast, we observed a relatively high dynamic when looking at the demographic processes more closely. About 11% of the trees found alive in 2010 died until 2019, resulting in an annual mortality rate of 1.3%. Ingrowing trees compensated for trees that died or decayed regarding tree density, but only to a small extent regarding volume. The volume lost was largely compensated by the growth (8.0 m(3) ha(-1) year(-1)) of the surviving trees. This work characterizes the change of forest attributes in a primeval beech forest at the landscape scale over a time of period of nine years and provides baseline indicators on the development and dynamics of primeval beech forests. It broadens our understanding about the contribution of the main demographic processes to the pronounced structural and compositional continuity of primeval beech forests.