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Allgemeine Forst- und Jagdzeitung, 184. Jg. (5/6), 97-112 (2013)
Rindenschäden durch Holzernte: Analyse, Modellierung und Evaluierung auf der Basis zweier Praxis-Großversuche.
... Therefore, the objective of this study was to provide a precise quantitative analysis of the impact factors in order to support decision making with respect to economic management of harvest-induced bark damage. For this, we used a bark damage prognosis model previously developed from a comprehensive database (Nill 2011;Nakou et al. 2013) as a "precursor" model and attempted to improve the model by applying and comparing the effect of three different, more complex modelling approaches (boosted regression trees, generalised linear mixed effects model and Bayesian Markov chain Monte Carlo generalised linear mixed models). ...
... The selection processes of the variables included in the model and the modelling method are described in detail in Nill (2011). Later on, Nill's model was evaluated and subsequently slightly modified (Nakou et al. 2013). ...
... Finally, the results of the three introduced modelling approaches and their results provided important information for optimising Nill's prototype GLMM-based bark damage prognosis model (Nill 2011;Nakou et al. 2013). Specifically, the predictor variable "sampling point is located on skid trail", representing in Nill's model proximity to a skid trail, displayed significant collinearity in the new model with the variables "mean skidding distance" and "distance of tree to skid trail" and was therefore subsequently removed. ...
Key message
We provided a precise quantitative analysis of the factors at the origin of bark damage during harvesting operations and developed a model able to predict them accurately. The major factors were the distance of trees to skid trails, the intensity of removals, the harvesting system as well as the interactions between the distance of trees to skid trails with harvesting systems, the average skidding distance, the tree species and tree height.
• Context
During timber harvesting, trees in the remaining stand may suffer bark damage resulting from tree-felling or log manipulation. Although a multitude of case studies and empirical observations provide qualitative and quantitative information with respect to the potential causal factors, the basic quantitative relationship between major factors of influence and the resulting degree of bark damage remains largely unclear.
• Aims
The objective was to provide a precise quantitative analysis of impact factors explaining the occurrence of bark damage during harvesting operations.
• Methods
Three different modelling approaches were tested: boosted regression tree (BRT), a generalised linear mixed effects model (GLMM) and Bayesian Markov chain Monte Carlo generalised linear mixed models (MCMCglmm).
• Results
The major factors with a significant impact on the occurrence of bark damage were the distance of trees to skid trails, the intensity of removals, the harvesting system and the interaction term between the distance of trees to skid trails with harvesting systems, average skidding distance, tree species and tree height.
• Conclusion
The final model includes the relevant major factors impacting on the infliction of bark damage during practical harvesting operations. Furthermore, it discriminates well with respect to the occurrence of bark damage, and it provides managers with a rational and conclusive tool for optimising harvesting operations.
... As a consequence, characteristics of the bark surface indicating past felling damage-even if complete occlusion of the wounds has occurred-are clearly indicative of reduced timber quality. Therefore, if the objective is the production of valuable beech timber, it is of utmost importance that felling damage is restricted to a minimum by applying appropriate low-damage techniques (Nakou et al. 2013) and/or by paying particular attention to maintaining future crop trees (Hein et al. 2007) from damage when felling in their vicinity. ...
Key messageBeech is subjected to devaluating bark damage by logging operations. It is shown experimentally that damage in the upper part of the trunk entails much higher risk of wood discoloration and decay by fungi than damage in the lower part. Cellular defense mechanisms in xylem are elucidated.ContextDuring harvesting operations and more specifically processes of both felling and extraction, remaining trees suffer specific bark damages, leaving the exposed xylem vulnerable to subsequent discoloration and fungal decay. As a consequence, the future value of the produced timber is reduced.AimsThe objective of this study is to test for the consequences of artificial bark damage to the base vs. the upper parts of the trunk in terms of discoloration, fungal infection, wood decay, and wound closure.Methods
An artificial basal “extraction wound” was inflicted along with an elongated “felling wound” at 5-m stem height in 40 beech trees (Fagus sylvatica L.) during either June or October. The trees were felled 3 years later and the impact of the wounds was evaluated with microscopic imaging and microbiological methods.ResultsThe compartmentalization observed in the basal extraction wounds was highly efficient, and rate and intensity of discoloration and susceptibility to decay were significantly lower than in wounds inflicted to the upper segments of the trunk. The latter displayed deeply penetrating discoloration and decay.Conclusion
Bark damage in the higher portions of the stem inflicted by felling is followed by much higher risk of wood discoloration and decay than damage at the base of the stem (extraction damage). Harvesting management has to be optimized in order to avoid felling damage in remaining neighboring trees particularly.
Bark wounds by damage during harvesting are a serious problem in forestry due to fungi infection and wood deterioration. This paper presents results of an investigation about the influence of the wounds on the internal structure of such injured stems. In an experiment, bark wounds were artificially created at the stem base of Norway spruce [Picea abies (L.) Karst.] and silver fir (Abies alba Mill.). 2 years later, the injured stems along with undamaged controls were cut and the trunk portion below breast height subjected to computer tomographic (CT) analysis. Analysis of the CT-images revealed a substantial impact of wounding on sapwood properties in spruce: directly adjacent to the wound surface in all examined trees, a large disturbance zone was detected affecting on average 17% of the potential sapwood area. With increasing distance from the wound, the size of this disturbance zone diminished, but was still detectable in all trees at breast height ca. 1 m above the bark wound.
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