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1.
Meritve gostote lesa v slovenskih gozdovih
Luka Krajnc, Jožica Gričar, Andreja Vedenik, Polona Hafner, Primož Simončič, 2020

Povzetek: V prispevku je predstavljen primer raziskave o variabilnosti kakovosti lesa različnih drevesnih vrst v slovenskih gozdovih. Meritve gostote, ki je eden glavnih pokazateljev kakovosti lesa, bodo služile za izdelavo podatkovne baze za oceno prostorske variabilnosti kakovosti lesa v Sloveniji. Zanesljivih in objektivnih podatkov o kakovosti lesa v naših gozdovih je relativno malo. Takšne baze so na ravni Slovenije izjemno pomembne, saj omogočajo vpogled v kakovost lesa, ki bo v prihodnje na voljo kot surovina na trgu za domačo lesno industrijo. Podobne baze bodo pomembne za izračun količine vezanega ogljika v nadzemni in podzemni biomasi za Slovenijo, hkrati pa bodo zbrani podatki služili tudi kot izhodišče za nadaljnje analize kakovosti lesa, zlasti mehanske lastnosti, ki so ključne pri uporabi lesa za konstrukcijske namene. Lastnosti in razpoložljivost lesa ekonomsko pomembnih drevesnih vrst so osnova za razvoj gozdno-lesne verige glede novih tehnologij, razvoja novih biomaterialov in potenciala rabe lesa različnih kakovosti z optimalnimi izkoristki.
Ključne besede: rezistograf, gostota lesa, kakovost lesa, listavci, iglavci
DiRROS - Objavljeno: 09.08.2020; Ogledov: 570; Prenosov: 193
.pdf Celotno besedilo (235,34 KB)

2.
Umerjanje rezistografskih meritev gostote lesa na stoječih drevesih : pretvorba v osnovno gostoto
Primož Simončič, Jožica Gričar, Polona Hafner, Luka Krajnc, 2020

Povzetek: V prispevku predstavljamo proces in rezultate določitve korekcijskih količnikov za pretvorbo rezistografskih gostot, izmerjenih na stoječih drevesih, v osnovno gostoto lesa na primeru bukve (Fagus sylvatica L.), puhastega hrasta (Quercus pubescens Willd.) in črnega bora (Pinus nigraArnold.). Korekcijski količniki so bili določeni na podlagi sveže odžaganih kolutov, ki so bili povrtani z rezistografom. Kolute smo stehtali, izmerili njihovo prostornino ter jih posušili do absolutno suhega stanja. Iz zbranih podatkov smo nato izračunali osnovno gostoto lesa ter korekcijske količnike med osnovno in rezistografsko gostoto. V raziskavo je bilo zajetih 59 kolutov. Aritmetična sredina vseh izmerjenih količnikov znaša 1,41, vrednosti 95 % intervala zaupanja pa znašajo od 1,38 do 1,46. Razlike med drevesnimi vrstami so statistično neznačilne. Rezistografska gostota relativno dobro odraža osnovno gostoto kolutov (Pearsonov korelacijski koeficient = 0,91; p < 0,001), kar nakazuje na relativno dobro povezanost osnovnih gostot kolutov z rezistografskimi gostotami. Dobljeni rezultati so ključnega pomena za nadaljnji razvoj področja merjenja dejanskih gostot lesa v stoječih drevesih na hiter in relativno nedestruktiven način.
Ključne besede: rezistograf, gostota lesa, kakovost lesa, bukev, puhasti hrast, črni bor
DiRROS - Objavljeno: 14.12.2020; Ogledov: 301; Prenosov: 100
.pdf Celotno besedilo (183,02 KB)

3.
The effect of bedrock and species mixture on wood density and radial wood increment in pubescent oak and black pine
Jožica Gričar, Polona Hafner, Luka Krajnc, 2020

Povzetek: Wood density and radial wood increment were examined in trees of pubescent oak (Quercus pubescens Willd.) and black pine (Pinus nigra Arnold., subsp. nigra) in relation to stand mixture and underlying bedrock. Trees of both species from pure and mixed stands were sampled across two types of bedrock, limestone and flysch. Trees from each species were similar in age. Wood density was estimated in standing trees using resistance drilling and increment cores were taken from a smaller subsample of trees of both species. Tree-ring, earlywood and latewood widths were measured and compared to radial profiles of wood density. The influence of stand mixture, diameter at breast height and bedrock on wood density was examined using a Bayesian general linear model. Wood density was significantly higher in pubescent oak than in black pine. Stand mixture was found to affect wood density positively, although the magnitude of the effect was relatively small when compared to other influencing factors also included in the current study. The effect of diameter on wood density was positive on both bedrocks in pubescent oak and negative or neutral in black pine. The size of the effect varied by bedrock and species. On flysch bedrock, the influence of diameter on wood density was stronger than it was on limestone. These indirect bedrock effects on wood density are probably a result of different soil fertility rather than the bedrock itself. There was a notable difference in radial wood increment in both species across the two bedrocks, whereas the differences in densities were smaller. Higher wood densities found on flysch in the subsample of pubescent oaks are likely an effect of higher proportions of latewood, while the opposite trend was observed in black pine. Higher wood density was found on limestone in black pine despite higher latewood percentages on flysch. In the context of forest management, the species composition of the naturally occurring mixtures in the sub-Mediterranean region should be adjusted slightly to favor pubescent oak, since it is a climax species and will bind more carbon for longer than black pine due to higher wood densities. Future forest management should also promote the overall development of pubescent oak trees in sub-Mediterranean stands. The results are especially important in the European context, because the share of sub-Mediterranean stands is expected to rise with global warming.
Ključne besede: Karst, wood structure, resistograph, resistance drilling, Quercus pubescens, Pinus nigra, limestone, flysch
DiRROS - Objavljeno: 14.01.2021; Ogledov: 125; Prenosov: 0
.pdf Celotno besedilo (1,42 MB)

4.
The effect of crown social class on bark thickness and sapwood moisture content in Norway spruce
Luka Krajnc, Jožica Gričar, 2020

Povzetek: The research study examined the effect of tree properties (crown social class, diameter at breast height (DBH), and tree height) on bark thickness (BT) and sapwood moisture content (SMC) in Norway spruce (Picea abies (L.) H. Karst.). Both examined variables were shown to be positively affected by DBH and tree height. The relationship between DBH and SMC varied among crown social classes, while the relationship between DBH and BT was relatively constant across crown social classes. Crown social class had a relatively small effect on BT and SMC, having a more pronounced effect on SMC than on BT. The relationship between tree height and BT did not vary across crown social classes, while the relationship between SMC and tree height was found to change slightly across crown social classes. Measurements of BT and SMC in the field are affordable, fast, and easy to use. Both variables could potentially be used to improve predictions of bark beetle attacks, as they reflect the physiological state of an individual tree.
Ključne besede: Picea abies, tree diameter, tree height, crown social class, phloem, sapwood
DiRROS - Objavljeno: 14.01.2021; Ogledov: 260; Prenosov: 331
.pdf Celotno besedilo (968,46 KB)

5.
Gostota lesa - metode določanja in pomen pri razvoju gozdno lesnega biogospodarstva
Domen Arnič, Miha Humar, Davor Kržišnik, Luka Krajnc, Peter Prislan, 2021

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
DiRROS - Objavljeno: 28.03.2021; Ogledov: 205; Prenosov: 133
.pdf Celotno besedilo (2,07 MB)

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