Diversity of patch structure in Central European forests: are tree diameter distributions in near‐natural multilayered Abies–Fagus stands heterogeneous?

Abstract

Near-natural multilayered Abies alba Mill.-Fagus sylvatica L. forests form structural mosaics and consist of patches in different developmental stages and phases. Knowledge of the diversity of patch structure and adequate methods to describe the diameter structure is essential for modeling forest dynamics. The hypotheses tested in the study are that near-natural multilayered stands are structurally heterogeneous (i.e., tree diameter (DBH) distributions of these stands are heterogeneous) and, that in these forests the finite-mixture models are suitable for modeling the empirical DBH distributions. Diversity of patch structure was studied based on data collected from 33 sample plots. In multilayered stands, four groups of empirical DBH distributions were distinguished using hierarchical cluster analysis (HCA) and correspondence analysis (CA). Stands investigated are structurally heterogeneous; 27% multilayered stands showed the slightly rotated sigmoid (SRS) type of empirical DBH distribution, 34% the distinctly rotated sigmoid (DRS) type, 18% the bimodal M-shaped (BMS) type, and 21% the unimodal highly skewed (UHS) type. The gamma distribution, the two-component mixture gamma model, and the two-component mixture Weibull model were more flexible for the SRS type of DBH distributions. The average p-values (Chi-square test) for these theoretical distributions were 0.4712, 0.4718, and 0.4660, respectively. The two-component mixture gamma model and the two-component mixture Weibull model were a good choice for modeling the DRS, BMS, and UHS types of DBH distributions. The average p-values (Chi-square test) for these models ranged from 0.2684 to 0.4854. In near-natural multilayered Abies-Fagus forest patches of different DBH distributions occur together.The empirical DBH distributions in these stands are characterized by irregular and complicated shapes and therefore are best approximated by finite-mixture models.

Modelling irregular and multimodal tree diameter distributions by finite mixture models: an approach to stand structure characterisation

“…Podlaski 2006Podlaski , 2010Podlaski and Zasada 2008). This type of regularity is most clearly observable in the case of the stands with typical multimodal DBH distributions.…”

“…In calculations of this sort, one should utilise various methods to choose initial parameter values for the MLE of mixture models (in particular the MM method; e.g. Zasada and Cieszewski 2005;Podlaski 2010). Three-component models ought to be utilised to describe multimodal DBH distributions for three-or multi-age cohort stands of complex structure.…”

“…The Weibull and gamma distributions are most commonly employed in this regard (e.g. Podlaski 2010). For this reason, DBH distribution models are used in ecology to simulate stand development (e.g.…”

Tree size distribution at increasing spatial scales converges to the rotated sigmoid curve in two old-growth beech stands of the Italian Apennines

“…It is worth noting that in the dominant stratum of beech old-growth forests, tree age cannot be easily inferred from stem size (Piovesan et al, 2005b(Piovesan et al, , 2010 because structural dynamics, in a very fine grain mosaic, condition individual life history. Such complex structures, also described by mixtures of theoretical size distributions, are now increasingly being reported for uneven-aged, pure or mixed, beech forests (Paluch, 2007;Podlaski, 2010). When size distribution follows the rotated sigmoid shape, these structures have been placed outside of the forest cycle and described as a ''steady state'' (Král et al, 2010).…”

Natural regeneration in the ‘Czmoń’ nature reserve (Wielkopolska Region)

“…Spatial diversity of vegetation in the forests of the temperate climate creates a unique microclimate, significantly affecting the state of the regeneration process (Podlaski 2010). The 'Czmoń' nature reserve, despite the varying degree of stand degeneracy, creates generally good conditions for natural regeneration of the forest.…”