1721 research outputs found
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Absence of juvenile effects confirmed in stable carbon and oxygen isotopes of european larch trees
No full textČlanek obravnava razmerja ogljikovih in kisikovih izotopov v branikah blizu stržena na prsni višini (cca 1,2 m) treh evropskih macesnov (Larix decidua Mill.), rastočih v mešanem gozdu s predraslimi hrasti in nasajenimi evropskimi macesni v zahodnem Walesu, Velika Britanija. Neklimatskega naraščajočega trenda v razmerjih ogljikovih izotopov, ki ga je sicer opaziti pri drugih vrstah v letih juvenilne rasti, ni, in tudi razmerje stabilnih izotopov ne kaže pomembnih trendov med odraščanjem drevesa. Rezultati iz prvih desetih branik ob strženu se bistveno ne razlikujejo od naslednjih dveh nizov desetih branik. O izostanku juvenilnega efekta v ogljikovih izotopih evropskega macesna so že poročali v zvezi z macesni, rastočimi v nesklenjenih sestojih v Franciji in to pripisali nezastrtosti krošenj in posledične neuporabe ogljikovega dioksida, ki ga pri dihanju oddajajo drevesa. Analizirana drevesa v zahodnem Walesu so rasla v nasadu s predraslimi hrasti, ki so bili starejši od podraslih macesnov. Macesni, kot svetloljubne drevesne vrste, so morali tekmovati za prostor in svetlobo, zato domnevamo, da je morebiten pojav juvenilnega efekta pri stabilnih izotopih prej posledica sprememb v hidravlični prevodnosti lesa, kot pa česa drugega. Ker današnja praksa izogibanja juvenilnega lesa omejuje potencial stabilnih izotopov drevesnih branik za dendroklimatološke in fiziološke raziskave, bi bile potrebnih dodatne raziskave o učinkih juvenilne rasti na pojav juvenilnega efekta v meritvah stabilnih izotopov
Structure and function of intra-annual density fluctuations
No full textTree rings are natural archives of climate and environmental information with a yearly resolution. Indeed, wood anatomical, chemical, and other properties of tree rings are a synthesis of several intrinsic and external factors, and their interaction during tree growth. In particular, Intra-Annual Density Fluctuations (IADFs) can be considered as tree-ring anomalies that can be used to better understand tree growth and to reconstruct past climate conditions with intra-annual resolution. However, the ecophysiological processes behind IADF formation, as well as their functional impact, remain unclear. Are IADFs resulting from a prompt adjustment to fluctuations in environmental conditions to avoid stressful conditions and/or to take advantage from favorable conditions? In this paper we discuss: (1) the influence of climatic factors on the formation of IADFs; (2) the occurrence of IADFs in different species and environments; (3) the potential of new approaches to study IADFs and identify their triggering factors. Our final aim is to underscore the advantages offered by network analyses of data and the importance of high-resolution measurements to gain insight into IADFs formation processes and their relations with climatic conditions, including extreme weather events
Living on the Edge: Contrasted Wood-Formation Dynamics in Fagus sylvatica and Pinus sylvestris under Mediterranean Conditions
No full textWood formation in European beech (Fagus sylvatica L.) and Scots pine (Pinus sylvestris L.) was intra-annually monitored to examine plastic responses of the xylem phenology according to altitude in one of the southernmost areas of their distribution range, i.e., in the Moncayo Natural Park, Spain. The monitoring was done from 2011 to 2013 at 1180 and 1580 m a.s.l., corresponding to the lower and upper limits of European beech forest in this region. Microcores containing phloem, cambium and xylem were collected biweekly from twenty-four trees from the beginning of March to the end of November to assess the different phases of wood formation. The samples were prepared for light microscopy to observe the following phenological phases: onset and end of cell production, onset and end of secondary wall formation in xylem cells and onset of cell maturation. The temporal dynamics of wood formation widely differed among years, altitudes and tree species. For Fagus sylvatica, the onset of cambial activity varied between the first week of May and the third week of June. Cambial activity then slowed down and stopped in summer, resulting in a length of growing season of 48–75 days. In contrast, the growing season for P. sylvestris started earlier and cambium remained active in autumn, leading to a period of activity varying from 139-170 days. The intra-annual wood-formation pattern is site and species-specific. Comparison with other studies shows a clear latitudinal trend in the duration of wood formation, positive for Fagus sylvatica and negative for P. sylvestris
The impact of disturbance-free areas on annual harvest operations planning
No full textThe article deals with annual harvest operations (AHO) planning with consideration of disturbance-free areas. We developed two models of binary integer linear programming (BILP) for scheduling work groups to harvest unit areas (HUA) according to the lowest possible cost. Total AHO costs include: harvesting and skidding costs, transportation costs, and machine relocation costs. First model is based on the presumption that harvesting can be planned and executed freely throughout the year. In the second model, scheduling was subject to time restrictions due to disturbance-free areas. 50% of the HUA had time restrictions which led to 16.9% reduction of annual workplace time. In this case, by introducing an extra work group, we can provide for the implementation of the AHO plan. Furthermore, we state that in this situation time restrictions affect the scheduling of work groups and the sequencing of tasks. The increase in total AHO costs can be explained by decreased wood harvesting capacity, increased production costs and higher amortization costs of machines. Available workplace time shortage due to time restrictions can be dealt with by shifting own workers to other tasks. The workforce deficits can be compensated by recruiting subcontractors. We have tested each model on two examples
Promotion activities of wood industry in Slovenia and in Croatia
No full textWood industry is among the most important industrial sectors in Slovenia and Croatia. In both countries, wood sector is a part of the national strategy plans and one of the industrial branches considered national economy boosters. But media coverage of wood industry and furniture manufacturing in Slovenia, as well as in Croatia, is far behind the promotion enjoyed by other industrial branches. This paper will give the current situation in promotional activities of wood sector in Slovenian and Croatian media and demonstrate the existing differences among given countries. Also, it will present some ideas on improving this situation according to media share of other highly profiled industrial branches in some southeastern European countries
Sistemski problemi obnove gozdov: povzetki referatov 3. znanstvenega srečanja Gozd in les, Ljubljana, 24. novembra 2016
Full text linkDecision making matrix for the selection of environmentally friendly harvesting system in the production of green wood chips
No full textue to the rising prices of fossil fuels and promotion of renewable energy sources, we recently witnessed the growing demands of the public for the exploitation of renewable biomass potentials. Slovenian legislation very rigidly defines utilization of logging residues and the production of green chips. In practice, this allows uncontrolled actions that bring new technologies, which raises a number of issues particularly with regard to environmental and ecological burdens. This paper presents a methodological approach used at design of the decision-making tool for the selection of environmentally friendly harvesting system in the production of green woodchips by considering various ecological and technological factors. Basically, a threestep methodological process is used, where in the first step soil and terrain are defined, in the second step, harvesting systems taking into account the diversity in terms of economic impact and ecological suitability are proposed and, last but not least, harvesting systems are placed into decision matrix taking into account technological and environmental constraints of different harvesting systems. The article also suggests 13 harvesting systems that are arranged into decision-making matrix taking into account the ecological, technological aspects in the production of green woodchips
Scleroderma areolatum ectomycorrhiza on Fagus sylvatica L.
No full textDespite its broad host range and distribution and its potential applications in commercial plantation forests, comprehensive descriptions of Scleroderma ectomycorrhizae are available only for Scleroderma citrinum, Scleroderma bovista and Scleroderma sinnamariense. This study provides a morphological and anatomical description of tree nursery derived ectomycorrhizae of Scleroderma areolatum on Fagus sylvatica, grown for several years in a climatized room. Ectomycorrhizae of S. areolatum were silvery white with abundant rhizomorphs; all mantle layers were plectenchymatous, rhizomorphs of type E, with prominent emanating hyphae with thick cell wall. The distal ends of emanating hyphae of rhizomorphs were inflated and often merged with other emanating hyphae. All parts of the mycorrhiza were clampless. In hyphae of the outer mantle layer, rhizomorphs and emanating hyphae, oily droplets were observed that did not stain in sulfo-vanillin and disappeared in lactic acid after a few hours. Although the phylogenetic analysis positioned the newly described ectomycorrhiza together with Scleroderma verrucosum and Scleroderma cepa in a single clade with a taxon name SH005470.07FU, the ectomycorrhizae of these three species can be morphologically well separated based on rhizomorph type
Formation of xylem and phloem in Europena beech tree after ice storm damage
No full textAfter the severe ice storm in 2014, numerous damaged trees were not removed from forests. Due to the lack of general knowledge about the processes occurring in damaged trees, a study involving 14 European beeches was conducted in the Arboretum Volčji Potok. Trees were categorized by crown injury; injury class K % undamaged, A % damaged less than 50 %, B % damaged between 50 and 75 %, and C % damaged more than 75 %. During the 2014 growing season, micro-cores were collected every fortnight using a Trephor tool. Changes in crowns were also observed and noted. Transverse sections of micro-cores were prepared and observed using light microscopy and an image analysis system. Xylem growth rings were 20 to 95 % narrower in damaged beech trees compared to the undamaged trees. Damaged trees also produced narrower phloem rings. The biggest differences in cambial activity in beech appeared between Class A and Class B
Comparison of motivation factors in two wood processing companies
No full textV raziskavi smo analizirali motivacijske in demotivacijske dejavnike med zaposlenimi v dveh lesno predelovalnih podjetjih. Raziskava je potekala v letih 2014 in 2015. Opravljena je bila z metodo anketiranja, s pomočjo vprašalnika, ki je vseboval šest vprašanj s ponujenimi možnimi odgovori. Vprašanja so bila zaprtega tipa, anketiranci pa so pomembnost vsebine posameznih odgovorov ocenjevali s štiristopenjsko lestvico. Anketiranih je bilo 180 zaposlenih v vsakem podjetju, rezultati pa so bili statistično obdelani s pomočjo %2 -testa in klasterske analize. S študijo smo ugotovili, da se najbolj pomembni motivacijski dejavniki med zaposlenimi v obravnavanih podjetjih bistveno razlikujejo. Zaposleni so najbolj zaskrbljeni glede socialnih potreb. Menijo tudi, da je v podjetju zelo pomembna psihološka klima. Motivacija zaposlenih je lahko povezana z večjo učinkovitostjo, višjo kakovostjo proizvodnje in poslovnimi rezultati, zato bi bilo treba takšne raziskave pogosteje opravljati