Abstract
Unmanaged forests are remnants of natural ecosystems that provide a basis for close-to-nature silvicultural research and applications. These forests have high amounts of dead wood, and although this material is being increasingly studied, the diversity of dead wood in terms of different diameters, decay stages, and spatial distribution patterns is as important as its volume for understanding forest dynamics. Here, we study natural forests in northern Iran to investigate the spatial distribution, decay stages, and volume of dead wood in unmanaged temperate forests at different developmental stages. Three stem-mapped sampling plots (100 m × 100 m) were established in uneven-aged stands dominated by Caspian beech (Fagus orientalis Lispsky). The total dead wood ranged from 37 to 119 m2 ha−1. Our results imply a spatial distribution shift from aggregation to randomness for dead trees in Caspian beech forest succession. We detected significant spatial interactions (attraction) between living and dead trees at short to medium spatial scales (1–20 m) in the plot with the earlier successional stage, suggesting that intra-specific competition is a prevailing force causing tree mortality at the stem-exclusion phase. By contrast, as trees become dominant with the mortality of other trees, the random tree-mortality pattern prevails. The spatial distribution and volume of dead wood may serve as a management target in near-to-natural Caspian beech forest. On the basis of our results, conservation-oriented management strategies should take into account the increasing amount of dead wood, particularly of large diameter in a late stage of decay.
Highlights
Uneven-aged forest stands have received increasing attention [1,2,3,4]
A total of 475 trees with diameter at breast height (DBH) of more than 7.5 cm were counted in the plot 1, including five tree species: F. orientalis, A. cappadocicum, A. velutinum, C. betulus, and A. subcordata (Table 1)
4% of this plot was covered by dead trees, 80% belonged to F. orientalis, and the rest were C. betulus
Summary
Uneven-aged forest stands have received increasing attention [1,2,3,4]. Unmanaged forests are remnants of natural ecosystems, providing a basis for nature-based forest management, i.e., to use natural forest ecosystems as a model and to guide forest management [2]. Natural forests are characterized by high amounts of dead wood of different sizes in all stages of decay, as well as by the presence of old and hollow trees [5,6]. The diversity of dead wood in terms of different diameters, decay stages, and spatial distribution patterns is as important as its volume [10]. Spatial-pattern analysis is a common tool in forest ecology, used to infer important processes of tree population dynamics [11,12]. In the absence of growth data, the analysis of the spatial patterns of observed tree mortality enable us to infer competitive interactions among trees within the stand [13], these constituting a fundamental ecological driver regulating growth, survival, and tree-species coexistence [14,15,16]
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