DIGITALNA ARHIVA ŠUMARSKOG LISTA
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V. Račko, M. Saniga, I. Čunderlík: THE IMPACT OF SILVICULTURALTREATMENTS ON THE STRUCTURE ...Šumarski list br. 9–10, CXXXV (2011), 437-448 DISCUSSION – Rasprava To start with, it is necessary to remember that the analyzed experiment is based on the exact data on change dynamics of chosen dendrometric parameters of chosen trees of the same ecotype in the same ecological and geological conditions with a different silviculture technique. Homogenization of ecological and geological conditions creates assumptions to find a relatively clear answer to the questions on the influence of different silviculture techniques on the formation of RH for beech. The results confirmed that autonomous and long- term position of beech trees with the crown length longer than a half of a tree height in the upper layer of selection system forest (CMT513) creates conditions to achieve target DBH of 45–50cm (age 100–110 years) with a very low assumption of RH formation. Similar results were achieved in case of crown thinning with a positive selection (CMT514b) and grading its relative thinning strength to24–26% of the taken volume capacity of beechstand in the age of 80 years. To achieve target beech diameter in the age of 100–110 years it is necessary to form its crown according to the above mentioned parameters (Mahlerand Höwecke 1991). By this way the assumptions are created for fully functional activity of the whole section of a trunk.The found parameters correspond with the requirements ofBachmann(1990)for quality forming of the lower third of a trunk which in case of beech presents 60% of its volume and up to 90% of its value production. The achieved results about frequency of RH confirmed that we can help to decrease it by the different way of silviculture treatment. Especially the selection system achieved considerably lower frequency of RH (Fig. 5). In comparison with literature (Mahlerand Höwecke1991)it was considerably lower for the same age of 100-120 years and for the trunk diameter at the DBH 40–49 cm. By Prka (2003), who investigated this issue of beech stands in a regeneration phase in the age of 100 to 110 years, the frequency of RH was approximately 50%. The issue of the changing size of DZ (Table 4) can be understood as an important restricting factor of formation and size of RH.Therefore, a keyfactor ofinjurieson the bottom of tree waspartiallyeliminated by a widezone ofSW.The air entering into the trunk had to overcome a bigger distance between the trunk surface and DZ. Largeinjuries at the bottom occurredonly inafew cases (Fig. 6a), more often small wounds were closedby new formed wound wood even before air enteringinto DZ (Fig. 6b). With changing CA at the different height of a trunk there appears the change of DZ width (Table 5). From the viewpoint of frequency of RH it is apparent that the RH occurred especially in the parts of trunk with higher CAand predominantly in those trees where the DZ was wider. However, we can see from the Table 6 that RH was formed in a few cases in the upper parts of trunk. Wernsdörferet al. (2005)pointed that only some wounds and branch marks on the bark are responsible for the RH formation.Torelli(2001)defines the formation of dry central zone in the middle of a beech trunk as a dynamic process analogical towards the RH formation for other wood species, while a tree adjusts the SW size (active transpiration area) to the crown size. In general, it applies that the age has a dominant influence on ageing and dieback of parenchyma and so on the increase of DZ portion at the expense of SW (Bosshard1965). On the other hand,the influence of crown volume contributes to alteration of portion between SW and DZ width (Torelli1974, 1984).Also, quality of the crown (leaves size, foliage density, ration of shadowy and lighted leaves as well as their proportional or disproportional distribution) have influence on average annual growth ring width (Assmann1961)and transpiration flow of water through the trunk (Bartelink 1997, Deckmyn et al. 2006).This must consequently show at the higher capacity of vital parenchyma which is capable to fulfill a supplying function in a tree. However, the crown development ofhealthytreesshouldbe understoodas a dynamicprocess, whichismainlyinfluenced byageandperformed thinning activities. Different methodsof thinning activitiesperformed on investigatedCMTsinthe last23yearscausedthat the averagecrownvolumes (apart from the last 8 years) differed significantly(Table 3). Itcaused differences in final average DZportions(Table 4). The achieved results entitle us to assume that even in the higher age of trees it is possible to influence positively the ratio between SWand DZ by a suitable silviculture activity leading to an increase of the crown size and quality from the photosynthesis point of view and so contribute to a decrease of frequency of occurrence and size of RH.This will consequently show at the quality and price of the produced assortments. ACKNOWLEDGMENTS – Zahvala This publication is the result of the project imple-Research & Development Operational Programme fun- mentation Centre of Excellence „Adaptive Forest Eco-ded by the ERDF. systems“, ITMS: 26220120006, supported by the |