1721 research outputs found
Sort by
Beech wood – correlations between the quality of trees, logs and sawn wood
No full textThe research addresses beech wood, from a standing tree to sawn wood. It focuses on the quality evaluation of individual trees and its impact on the later products made of the respective wood. For the needs of observing the quality of standing trees, the current 5-class scale for quality evaluation of the Slovenia Forest Service (SFS) was used. To evaluate the wood assortment,
the SIST EN 1316-1:2013 standard was applied, while the evaluation of sawn wood was performed as per the rules of the European Organisation of the Sawmill Industry (EOS). On the basis of the sample of evaluated and eventually harvested trees, the correlations between the quality of trees, roundwood products made of them and the quality of final sawn products were established. The sample equally included trees of all five quality classes. The production of wood assortment provided the most logs of B quality (51%) and the highest quantity of sawn wood of EOS-C quality (52%). Beech trees of excellent quality
provided 35% of the wood assortment of highest quality and these provided 8% of the sawn wood of the highest quality. The key criteria for the classification by quality were covered knots for forest products and dead and unsound knots for sawn wood
Towards a common methodology for developing logistic tree mortality models based on ring-width data
No full textTree mortality is a key process shaping forest dynamics. Thus, there is a growing need for indicators of the likelihood of tree death. During the last decades, an increasing number of tree-ring based studies have aimed to derive growth-mortality functions, mostly using logistic models. The results of these studies, however, are difficult to compare and synthesize due to the diversity of approaches used for the sampling strategy (number and characteristics of ‘alive’ and ‘death’ observations), the type of explanatory growth variables included (level, trend, etc.), and the length of the time-window (number of years preceding the alive/death observation) that maximized the discrimination ability of each growth variable.
Here, we assess the implications of key methodological decisions when developing tree-ring based growth-mortality relationships using logistic mixed-effects regression models. As examples we use published tree-ring datasets from Abies alba (13 different sites), Nothofagus dombeyi (one site) and Quercus petraea (one site). Our approach is based on a constant sampling size and aims at (1) assessing the dependency of growth-mortality relationships on the statistical sampling scheme used; (2) determining the type of explanatory growth variables that should be considered; and (3) identifying the best length of the time window used to calculate them.
The performance of tree-ring based mortality models was reasonably high for all three species (Area Under the receiving operator characteristics Curve: AUC > 0.7). Growth level variables were the most important predictors of mortality probability for two species (A. alba, N. dombeyi), while growth-trend variables need to be considered for Q. petraea. In addition, the length of the time window used to calculate each growth variable was highly uncertain and depended on the sampling scheme, as some growth-mortality relationships varied with tree age.
The present study accounts for the main sampling-related biases to determine reliable species-specific growth-mortality relationships. Our results highlight the importance of using a sampling strategy that is consistent with the research question. Moving towards a common methodology for developing reliable growth-mortality relationships is an important step towards improving our understanding of tree mortality across species and its representation in dynamic vegetation models
Timing of False Ring Formation in Pinus halepensis and Arbutus unedo in Southern Italy: Outlook from an Analysis of Xylogenesis and Tree-Ring Chronologies
No full textMediterranean tree rings are characterized by intra-annual density fluctuations (IADFs) due to partly climate-driven cambial activity. IADFs are used as structural signals to gain information on relations between environmental conditions and eco-physiological processes during xylogenesis, with intra-annual resolution. To reach an unbiased synchronization of the IADF position within tree rings and seasonal fluctuations in environmental conditions, it is necessary to know the timing of cambial activity and wood formation, which are species- and site-specific processes. We applied the microcoring technique to analyze xylogenesis in Pinus halepensis and Arbutus unedo. To the best of our knowledge, this is the first attempt to study xylogenesis in a hardwood species forming frequent IADFs. Both species co-occur at a site in southern Italy characterized by a Mediterranean climate. To facilitate tree-ring dating and identification of IADFs, we performed traditional dendroecological analysis. We analyzed xylogenesis during summer, which is considered a constraint for xylogenesis and a trigger for IADF formation. We followed the different phases of cell development in the current wood increment with the aim of evaluating whether and which type of IADFs were formed. We additionally analyzed the same phases again in September and in winter to verify the possible formation of IADFs in fall and whether cell production and differentiation was completed by the end of the calendar year. Both species formed the same type of IADFs (earlywood-like cells within latewood), due to temporary growth restoration triggered by rain events during the period of summer drought. At the end of the calendar year, no cells in the phases of enlargement and secondary cell wall deposition occurred. A. unedo was more sensitive than P. halepensis because IADFs were formed earlier in the season and were more frequent in the tree-ring series. The dendro-anatomical approach, combining analysis of tree-ring series and of xylogenesis, helped to detect the period of IADF formation in the two species. Results are discussed in functional terms, highlighting the environmental conditions triggering IADFs, and also in methodological terms, evaluating the applicability of xylogenesis analysis in Mediterranean woods, especially when the formation of IADFs is not uniform around the stem
Model of solving conflicts - Croatian wood industry case
No full textIn business, as well as in all other relationships, there are different opinions and conflicts. Dealing with conflicts is one of the most important tasks of management which has a great influence on efficiency and success of a company. In the research, which was a subject of this article, we were studying the phenomena of conflict in a big wood industry company in Croatia. Data were collected by structured questionnaire survey. We were trying to establish characteristics of an existing model of dealing with conflicts in this particular company. We were more focused on relationship between employees, how often conflicts occur and how persons involved in conflict respond to it. Since in this particular company the model for dealing with conflicts formally does not exist, based on the research we were able to identify the model and prove its characteristics. Results showed that relationship between employees in researched company were good and that responses to conflicts were positive. The most frequent cause for conflicts is a poor information flow between employees, which showed the existing need for improving communication channels, especially by conversations and different meetings. Therefore, communication channels are one of the most important elements of the new model for solving conflict situations in this particular company
Waviness of beech sliced veneer
No full textIn wood industry, decorative veneer is a product of high added value. Although the technological process of sliced veneer is well known, its quality and price depend on many technological parameters of production, particularly on the quality of logs. The research, which was focused on the influence of visual defects of beech (Fagus sylvatica L.) logs and the impact of climatic conditions in the drying phase of sliced veneer on the surface veneer waviness, was conducted in an industrial environment. The results indicate that the largest share of waved veneer was cut from cracked logs (71%) and less from curved logs (20%). The veneer was sorted manually by experienced controllers from this branch of industry. Their subjective criteria can affect the accuracy of classification of veneer and, consequently, the research results. Therefore, the possibility of using 3D camera for measuring veneer waviness and grading the veneer into quality classes was examined
Assessing the forest's protective effect against avalanches : the case of Russian road below Vršič
No full textCesto na Vršič ogrožajo snežni plazovi, gozdovi nad njo pa opravljajo zaščitno in varovalno funkcijo pred njimi. Analizirali smo potencialno ogroženost dela ceste in gozda nad njo, opravili presojo zaščitne funkcije gozda pred snežnimi plazovi ter določili smernice in ukrepe za nadaljnji razvoj gozda in krepitev njegovega varovalnega učinka. Na objekt raziskave smo postavili mrežo 21 raziskovalnih ploskev. Po modificirani metodi NaiS (Frehner in sod., 2005) smo izločili in opisali sestoje ter primerjali njihovo dejansko stanje s ciljnim, ki zagotavlja zaščito pred snežnimi plazovi. Glede na naklon in pokritost z gozdom smo naredili karto, ki kaže najbolj ogrožena območja pred snežnimi plazovi. Ugotovili smo, da noben sestoj ne zagotavlja popolne in trajne zaščitne funkcije. Največji problem sta pomlajevanje in zagotavljanje raznomerne strukture sestojev. Najpomembnejše smernice za nadaljnji razvoj gozda so pospeševanje raznomerne in raznodobne strukture, zagotavljanje pomladka, vzgoja čim večjega števila nosilcev stabilnosti ter zagotavljanje dobre vitalnosti in zadostne gostote dreves
