Pavel Daněk

How cyclical and predictable are central European temperate forest dynamics in terms of developmental phases

Questions Recently there have been vital discussions about the validity of the European patch-mosaic conceptual model of forest dynamics – the traditional concept of a shifting patch-mosaic of developmental stages and phases, also known as the forest cycle concept. Here we try to answer the fundamental questions of this debate: How much do the forest dynamics proceed along a predictable path (in a chronological sequence: growth—optimum—breakdown)? Or vice versa, are the patches rather a result of disturbances and/or other stochastic growth and mortality patterns? Location The study was carried out at 5 long-term research plots located in 4 different study sites of central European natural temperate forests. Methods The long-term evolution of forest developmental phases was analyzed by a GIS based, spatially explicit, fully reproducible method enabling proper verification of the functionality of the model forest cycle. We analyzed long-term transitions among forest developmental phases from the 1970s through the 1990s to 2000s. Observed phase-to-phase transitions were compared to a random transition model. We identified preferential pathways within the forest cycle model as well as the proportion of cyclic/ acyclic transitions. Results In total, across all sites and observation periods about 65% of all observed phase-to-phase transitions were realized through preferential pathways, about 28% of observed transitions went along pathways of random frequency and only about 7% of observed transitions were realized through uncommon developmental pathways. On the other hand, only less than 40% of all observed transitions might be classified as cyclic (following the model cycle), and thus more than 60% of the transitions were acyclic (moving across or backward in the model cycle). The overall pattern of all observed transitions resembled a complex web rather than a simple repeating cycle. Conclusions Although in all sites we documented signs of the cyclic and predictable development anticipated by the forest cycle concept, the predominance and stochastic nature of multiple acyclic developmental pathways gave rise to reasonable doubts on the legitimacy and usability of the concept for descriptions of forest dynamics. On the other hand, the verification of the concept may contribute significantly to our understanding of the complexity of forest dynamics. This article is protected by copyright. All rights reserved.

Biomechanical effects of trees in an old-growth temperate forest: Biomechanical effects of trees

The role of biomechanical effects of trees (BETs) in ecosystem and landscape dynamics is poorly understood. In this study, we aim to (i) describe a widely applicable methodology for quantifying the main BETs in soil, and (ii) analyze the actual frequencies, areas and soil volumes associated with these effects in a mountain temperate old-growth forest. The research took place in the Boubinsky Primeval Forest in the Czech Republic; this forest reserve, predominated by Fagus sylvatica L. and Picea abies (L.) Karst., is among the oldest protected areas in Europe. We evaluated the effects of 4000 standing and lying trees in an area of 10.2ha from the viewpoint of the following features: tree uprooting, root mounding, bioprotection, trunk baumsteins (rock fragments displaced by trunk growth), root baumsteins, stump hole infilling, trunk and root systems displacements, depressions formed after trunk fall, stemwash, and trunkwash. BETs were recorded in 59% of standing and 51% of lying dead trees (excluding the pervasive soil displacement by thickening trunks and roots and the infilling of decayed stumps). Approximately one tenth of the trees showed simultaneous bioprotective and bioerosion effects. Different tree species and size categories exhibited significantly different biomechanical effects. A bioprotective function was the most frequent phenomenon observed, while treethrows prevailed from the viewpoint of areas and soil volumes affected. The total area influenced by the BETs was 342m(2)ha(-1). An additional 774m(2)ha(-1) were occupied by older treethrow pit-mounds with already decayed uprooted trunks. The total volume of soil associated with the studied phenomena was 322m(3)ha(-1), and apart from treethrows, volumes of the living and decaying root systems and bioprotective functions predominated. Other processes were not so frequent but still significant for biogeomorphology. Copyright (c) 2017 John Wiley & Sons, Ltd.