Iskanje po repozitoriju

A+ | A- | | SLO | ENG

Povzetek: Gostota lesa je fizikalna lastnost, ki je enostavno določljiva in nakazuje na številne druge lastnosti lesa in s tem tudi na njegovo uporabnost v lesno-predelovalni industriji, gradbeništvu ali energetiki. Ker je odvisna od vlažnosti ter poroznosti, se v stroki pojavljajo različne definicije gostot lesa, med katerimi je največkrat uporabljena gostota lesa v absolutno suhem stanju. Namen prispevka je predstavitev različnih načinov določanja gostote lesa ter pomen hitrega in natančnega določanje tega parametra kakovosti pri razvoju gozdno lesnega biogospodarstva. V stroki obstaja več neposrednih in posrednih metod določanja gostote; najbolj običajen in razširjen je volumetrični pristop, sledi postopek ocenjevanja gostote s penetrometrom, rezistografom, visokofrekvenčno denzitometrijo, rentgenskimi žarki, infrardečo spektroskopijo ter mikrovalovi. Les je surovina, ki ji bo v prihodnosti pomen še naraščal, saj je ključna za razvoj trajnostnega biogospodarstva. Natančno in pravočasno določanje gostote lesa bo omogočalo ustrezno razporejanje in usmerjanje tokov te surovine med posameznimi konvencionalnimi in novimi sektorji (področji rabe) in posledično bolj učinkovito in trajnostno rabo.
Ključne besede: lastnosti lesa, gostota lesa, rezistograf, penetrometer, rentgenska denzitometrija, visokofrekvenčna denzitometrija, gozdno lesno biogospodarstvo
Objavljeno v DiRROS: 28.03.2021; Ogledov: 4161; Prenosov: 2498
Celotno besedilo (2,07 MB)
Gradivo ima več datotek! Več...

Povzetek: The understanding of spatial distribution patterns of native riparian tree species in Europe lacks accurate species distribution models (SDMs), since riparian forest habitats have a limited spatial extent and are strongly related to the associated watercourses, which needs to be represented in the environmental predictors. However, SDMs are urgently needed for adapting forest management to climate change, as well as for conservation and restoration of riparian forest ecosystems. For such an operative use, standard large-scale bioclimatic models alone are too coarse and frequently exclude relevant predictors. In this study, we compare a bioclimatic continent-wide model and a regional model based on climate, soil, and river data for central to south-eastern Europe, targeting seven riparian foundation species%Alnus glutinosa, Fraxinus angustifolia, F. excelsior, Populus nigra, Quercus robur, Ulmus laevis, and U. minor. The results emphasize the high importance of precise occurrence data and environmental predictors. Soil predictors were more important than bioclimatic variables, and river variables were partly of the same importance. In both models, five of the seven species were found to decrease in terms of future occurrence probability within the study area, whereas the results for two species were ambiguous. Nevertheless, both models predicted a dangerous loss of occurrence probability for economically and ecologically important tree species, likely leading to significant effects on forest composition and structure, as well as on provided ecosystem services.
Ključne besede: bioclimatic model, ecological niche model, forest management, tree species selection, riparian forest habitat, climate change adaptation
Objavljeno v DiRROS: 22.03.2021; Ogledov: 1255; Prenosov: 850
Celotno besedilo (2,47 MB)
Gradivo ima več datotek! Več...

Povzetek: In the last few decades, an increasing number and intensity of bark beetle outbreaks have plagued the forests of Europe and North America. Bark beetle management is directly related to forest owner characteristics, although this relationship is not well understood. The purpose of the study was to investigate the influence of forest owner characteristics on the amount and timing of sanitary felling under different disturbance regimes and quantities of Norway spruce. We combined different databases on sanitary felling, the timing of sanitary felling, and forest owner characteristics for Slovenia from 2014 to 2018 and analyzed the amount and timing of sanitary felling in relation to forest owner characteristics. We found that the timing in winter and the amount of sanitary felling were positively associated with the distance of the owner%s residence to the forest parcel. Larger parcels were more affected by bark beetles but did not have later timing of cutting in the summer period as was hypothesized. The timing of sanitary felling decreased with property size, while with the probability of sanitary felling, the effect of property depended on the ice storm and the amount of spruce. The size of the settlement, the permanent address of the private owner, and timing of sanitary felling were positively associated but also depended on the amount of spruce. Gender and age did not have an important influence on the amount and timing of sanitary felling. Forest owners are an important factor in effective bark beetle management. This study highlights the private forest ownership characteristics that should be emphasized in order to fight bark beetle outbreaks in the event of large-scale disturbances. Governments should support forest owners who are at greater risk of bark beetle outbreaks and less efficient in managing outbreaks. Furthermore, landowner characteristics should be included when forecasting bark beetle outbreaks.
Ključne besede: close-to-nature management, sanitary felling, Ips typographus, forest pest management, forest owner characteristics
Objavljeno v DiRROS: 22.03.2021; Ogledov: 1177; Prenosov: 825
Celotno besedilo (444,49 KB)
Gradivo ima več datotek! Več...

Povzetek: Climate change will affect radial growth patterns of trees, which will result in different forest productivity, wood properties, and timber quality. While many studies have been published on xylem phenology and anatomy lately, little is known about the phenology of earlywood and latewood formation, also in relation to cambial phenology. Even less information is available for phloem. Here, we examined year-to-year variability of the transition dates from earlywood to latewood and from early phloem to late phloem in Norway spruce (Picea abies) from three temperate sites, two in Slovenia and one in the Czech Republic. Data on xylem and phloem formation were collected during 2009-2011. Sensitivity analysis was performed to determine the specific contribution of growth rate and duration on wood and phloem production, separately for early and late formed parts. We found significant differences in the transition date from earlywood to latewood between the selected sites, but not between growth seasons in trees from the same site. It occurred in the first week of July at PAN and MEN and more than two weeks later at RAJ. The duration of earlywood formation was longer than that of latewood formation; from 31.4 days at PAN to 61.3 days at RAJ. In phloem, we found differences in transition date from early phloem to late phloem also between the analysed growth seasons; from 2.5 weeks at PAN to 4 weeks at RAJ Compared to the transition from earlywood to latewood the transition from early phloem to late phloem occurred 25-64 days earlier. There was no significant relationship between the onset of cambial cell production and the transition dates. The findings are important to better understand the inter-annual variability of these phenological events in spruce from three contrasting temperate sites, and how it is reflected in xylem and phloem anatomy.
Ključne besede: Picea abies, xylem formation, phloem formation, cambium, tracheid, sieve cell, conifer, temperate environment
Objavljeno v DiRROS: 22.03.2021; Ogledov: 1133; Prenosov: 830
Celotno besedilo (1,27 MB)
Gradivo ima več datotek! Več...

Objavljeno v DiRROS: 22.03.2021; Ogledov: 839; Prenosov: 397
Celotno besedilo (371,12 KB)
Gradivo ima več datotek! Več...