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Forest gaps, openings in the canopy caused by death of one or more trees, are the dominant form of natural disturbance in the temperate forests. Gaps play a critical role in driving stand dynamics and influencing forest growth cycle. They increase habitat diversity, structural complexity, fauna and flora species diversity. The size of a gap may strongly influence tree species regeneration composition, vegetation growth, nutrient cycling, microclimate and may have considerable effect on a number of biological processes. The main aim of this study was to understand the effects of gap size diversity on species composition and number of natural regeneration. The study was carried out in near−natural mixed stands dominated by beech (Fagus sylvatica L.) and silver fir (Abies alba Mill.) representing different development stages and phases in the Świętokrzyski National Park, (central Poland). All gaps over than 20 m 2 intersected by a transects line were sampled. All saplings and seedlings were counted in circular plots (10 m²) evenly spaced along the long axis in the N−S and E−W gradients of each gap. Natural regeneration was analyzed for 62 canopy gaps of various sizes. The gaps were classified into three size classes: small ≤100 m², medium 101−250 m² and large >250 m². The gap size ranged from 21 to 397 m², with a median of 104 m². The dominant tree species regenerated in gaps were fir (69%) and beech (24%). The number of regeneration significantly depended on the gap size (p=0.027). The highest frequency of saplings was found in gaps of ≤100 m². The number of natural regeneration was significantly negatively correlated with gap size (r=–0.261, p=0.040). The density of silver fir regeneration was significantly higher in gaps of ≤100 m² and 101−250 m² (p<0.05). The share of fir in stand species composition effected on the number of silver fir and European beech regeneration. The results of this study demonstrated the utility of gap−based approach for better understanding ecosystem responses to tree cutting for modern forest management.
The aim of the study was to present two issues concerning forests in the Sudety Mts. (SW Poland): 1) the process of tree mortality in individual years in the period between 2002 and 2018, as well as 2) the analysis of the radial growth of the main tree species (i.e. spruce, larch, beech, fir and Douglas fir). The intensity of the process of tree mortality is evidenced by the volume of wind−broken or wind−fallen trees and deadwood. The record volume of post−hurricane wood was harvested after the hurricane ‘Cyril’ (January 2007). The volume of wood removed in 2007−2008 amounted to 1.4 million m³. Quite a high share of wind−broken and wind−fallen trees in the volume of harvested wood raw material concerned the years 2002, 2003, 2006, 2008 and 2018. In the latter year, the damage was caused by the hurricane ‘Grzegorz’. The record removal of deadwood occurred in 2016 following an exceptionally severe drought in the 2015 growing season. The high volume of deadwood in 2017 and 2018 was augmented by quite a high volume of wind−broken and wind−fallen trees. Spruce and larch showed the strongest response to severe drought in 2015 by lowering the increment in diameter and producing a narrow layer of latewood, while the response of beech and Douglas fir was the slightest. No such response was found in fir. The main tree species in the Sudetes is spruce, which quickly disappears from this area. It is necessary to look for such species of trees that might replace spruce, i.e. species more suitable to changing climatic conditions, such as beech, oak, ash, sycamore, pine and larch – but also fir and Douglas fir. The latter two species show a high tolerance to changing climatic conditions, and a high potential in the production of wood.
In Poland, the majority of silver fir stands is characterised by a single−layer stand structure. The current silvicultural activities aim at obtaining multilayer stands, which requires a clearer definition of the structure, and more precisely, a better knowledge of the pattern of diameters at breast height (DBH) distribution. The aim of the research was to develop a pattern of DBH distribution of trees in a multilayer silver fir stand in the Świętokrzyskie Mountains (central Poland) using the BDq method, through the mathematical determination of function parameters, including the productive capacity of the habitat. The application of this pattern will allow the selection of the management methods aimed to obtain and then maintain model stands with a different layer structure. The research was based on the empirical material collected in 56 stands that were characterized by both a single− and a multi−layered structure. They grew in coniferous forest habitats, mostly in the upland mixed coniferous forest, upland mixed deciduous forest and upland deciduous forest or mountain forest. One big (up to 1 ha) or 3−5 smaller (0.04 ha) sample plots were established in each stand in which diameters at breast height of all trees and heights of usually 25 trees, selected from the entire range of diameters, were measured. These were used to determine the height growth curve equation coefficients and then the height of each tree. For each stand the basal area was calculated and a graph for DBH distribution was prepared. Site index was established using the original empirical equation. In order to develop a model for multilayer fir stands, individual parameters of the equation 5, such as the basal area (B), the target diameter at breast height (D) and the coefficient q were to be determined using the BDq method. Taking into consideration only stands with one−tailed DBH, individual parameters of the function were found to be associated with site index. Empirical equations were developed for the determination of B and D, and, based on the DBH distribution graphs, coefficient q associated with site index was also calculated (tab.). The developed DBH distribution pattern is a mathematical description of the target fir stand. When the value of stand parameters approaches those of the model stand, it should be managed using the shelterwood cutting system, which results from the spatial variation in the stand height structure, and consequently from the need for different silvicultural treatments in different stand fragments.
The paper presents the dendrochronological analysis of silver firs (Abies alba Mill.) growing in the canopy layer of the forest stands. We searched for the similarities in the rhythm of radial growth of studied trees and we analysed the response of these stands to the increment disturbances related to the occurrence of adverse climatic factors and the pressure from industrial pollution. The research material was collected in 30 pure and uneven−aged silver fir stands located in the Świetokrzyskie Mountains (central Poland). We investigated the effect of age of the stands and the conditions for their growth (location, forest habitat type) on an average tree−ring width. In order to detect similarities in the rhythm of radial growth of the surveyed stands, we grouped the raw chronologies by the means of the cluster analysis, using Ward's agglomeration procedure with 1−r distance (r – Pearson correlation coefficient). We assessed the incremental response of the investigated stands to the disturbances (situations of significantly reduced radial growth) using indicators of resistance, recovery and resilience proposed by Lloret et al. [2011]. We also studied the influence of the stand age and the forest habitat type on the response of analysed for stands to the detected disturbances. The shortest chronology consisted of 94 tree−rings, while the longest one of 137. Average length of the obtained silver fir chronologies was 119 years. Older fir stands characterised with narrower rings (r=–0.451, p=0.012). Neither the location, nor the forest habitat type are the factors determining the similarity of the rhythm of radial growth of silver firs from the Świętokrzyskie Mountains (p=0.243 and p=0.967 respectively). The extreme climatic conditions responsible for the majority of the short−term (one−year−long) incremental depressions are the factor of regional importance, which affects the growth of investigated trees. Older stands characterized with better possibilities of increment recovery after the disturbance than younger stands (p<0.001), which may be a result of the production of secondary crowns. No consistent differences in the indices of resistance and resilience were found among analysed stands.
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