Patterns of tree diameter distributions in managed and unmanaged Abies alba Mill. and Fagus sylvatica L. forest patches

Common ground among beech forest development stages: Matrix versus stage‐typical live tree structure

“…In these stands, differences among development stages had less to do with L and VL trees, which did not differ among stages (perhaps due to resistance to disturbance, Paluch, 2007), and more to do with changes in the proportions of VS, S, and M size classes, which could either reflect recent gap dynamics (i.e., small disturbances stimulating regeneration and release) or the continuous regeneration of shade-tolerant beech (providing an ongoing supply of VS trees), in both cases followed by neighborhood dynamics (resulting in size differentiation among trees regardless of age). Although it is beyond the scope of the current study to determine which processes explain observed structures, we agree with Akhavan et al (2012) that structural differences among stands in different development stages cannot arise only through dynamics that are common to all forested stands (i.e., neighborhood dynamics or continuous regen- (Nagel, Svoboda, Rugani, & Diaci, 2010;Wagner et al, 2010) and neighborhood dynamics (e.g., competition) exacerbate size differentiation among trees (Podlaski, Sobala, & Kocurek, 2019). Structure in natural beech forests is dominated by neighboring trees that often vary considerably in age (Drössler et al, 2016;Trotsiuk, Hobi, & Commarmot, 2012), due to a high tolerance for suppression (Piovesan, Di Filippo, Alessandrini, Biondi, & Schirone, 2005;Wagner et al, 2010) combined with a strong capacity for release (Korpeľ, 1995;Leibundgut, 1993;Schütz, 2001), which would be consistent with the wide span of tree sizes observed within these plenter-like matrix neighborhoods.…”

“…The findings of the current study appear most congruous with the temporal and spatial variation of gap dynamics resulting in variously aged, but relatively newer, gap patches (with relatively high within‐patch homogeneity) nested within a background matrix of highly heterogeneous neighborhoods emerging in the absence of recent disturbance. In the first part of this proposed model, the shared matrix structure we observed in all three development stages would be common to neighborhoods that have experienced relatively long periods of stability in which both the continuous regeneration of beech under an existing canopy (Nagel, Svoboda, Rugani, & Diaci, ; Wagner et al., ) and neighborhood dynamics (e.g., competition) exacerbate size differentiation among trees (Podlaski, Sobala, & Kocurek, ). Structure in natural beech forests is dominated by neighboring trees that often vary considerably in age (Drössler et al., ; Trotsiuk, Hobi, & Commarmot, ), due to a high tolerance for suppression (Piovesan, Di Filippo, Alessandrini, Biondi, & Schirone, ; Wagner et al., ) combined with a strong capacity for release (Korpeľ, ; Leibundgut, ; Schütz, ), which would be consistent with the wide span of tree sizes observed within these plenter‐like matrix neighborhoods.…”

“…However, the relatively homogeneous patches PECK and ZEnnER documented in natural beech forests tend to be small in spatial extent Meyer, Tabaku, & von Lüpke, 2003) and comprise only a small proportion of overall forest area (Drössler et al, 2016). The high heterogeneity commonly observed in beech forests (Meyer et al, 2003;Podlaski, 2019;Podlaski et al, 2019) reflects the combination of first-order hierarchical level (sensu Kotliar & Wiens, 1990) gap patches (which in aggregate constitute a second-order level of different phases) into the context of their surrounding matrix forest, constituting the higher (third-order) level that incorporates different-phase patches as well as the plenter-like background matrix. Thus, rather than being homogeneous representations of a given development stage, the 1-ha beech stands in the current study may have been classified into particular development stages due to a preponderance of neighborhoods with a given stagetypical structure, which could have arisen through temporally synchronized disturbance (i.e., an unequal rate of gap formation across the landscape).…”

Comparison of tree diameter distributions in managed and unmanaged Kazdağı fir forests

“…The complexity of the forest structure may enhance biodiversity (Gardner et al, 2009) and improve ecosystem services (Rutten et al, 2015). Forest structure consists of vertical and horizontal components and it is usually defined as species composition, size and distribution of trees, shrubs and ground cover vegetation (Podlaski et al, 2019). While vertical stand structure often refers to layering of tree crowns, horizontal structure mostly represents diameter size distribution and spatial patterns of tree species (Davis, Johnson, 1987).…”

“…Different vertical stand structures can be formed in forests of shade-tolerant tree species. Thus, the understanding of the linkage between diameter distribution patterns and future stand structure is essential for the successful and sustainable management of these forest types (Podlaski et al, 2019).…”