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Query: "author" (Milan Kobal) .

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Reconstruction of rockfall activity through dendrogeomorphology and a scar-counting approach : a study in a beech forest stand in the Trenta valley (Slovenian Alps)
Barbara Žabota, Daniel Trappmann, Tom Levanič, Milan Kobal, 2020, original scientific article

Abstract: Trees represent an important archive that can be used to reconstruct the spatial and temporal patterns of rockfall events. Rockfall impacts can be recorded in the form of anomalies in tree rings and impact scars on the tree stem. In this paper we demonstrate the use of an approach based on counting scars for reconstructing the frequency and spatial pattern of past rockfalls. The approach was applied by counting the visible scars on the stem surface of 52 European beech trees (Fagus sylvatica L.) in the area of the Trenta Valley, Slovenia. The average number of impacts per trees was 7, and the impacts were mostly classified as old, indicating reduced rockfall activity in recent years. The average recurrence interval was 31.8 years, which was reduced by 1.2 years by the application of the conditional impact probability. The spatial pattern of rockfall impacts shows that rockfall activity is higher in the middle part of the studied slope.
Keywords: rockfall, natural hazards, dendrogeomorphology, tree rings, stem scars, recurrence interval
Published in DiRROS: 01.04.2020; Views: 3894; Downloads: 2986
.pdf Full text (1,02 MB)

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The influence of abiotic and biotic disturbances on the protective effect of alpine forests against avalanches and rockfalls
Domen Oven, Barbara Žabota, Milan Kobal, 2020, review article

Abstract: Abiotic and biotic disturbances in alpine forests can reduce forest cover or change the structure of the forest and consequently reduce the protective effect of forest against natural hazards such as avalanches and rockfalls. In this review article, the effect of the main abiotic (forest fire, windthrow, ice break, snow break, avalanche and rockfall) and biotic (insects and pathogens) disturbances in protection forests are presented along with their potential influence on the protective effect of forest against avalanches and rockfalls. In general, natural disturbances negatively affect the protective effect of forest, especially in the case of large-scale and severe events, which in alpine areas are mostly caused by storms, bark beetle outbreaks, avalanches and forest fires. Climate change induced interactions between disturbances are expected to present challenges in the management of protection forests in the future.
Keywords: natural disturbances, natural hazards, abiotic disturbances, biotic disturbances, protection forests, protective effect, stand parameters, rockfall, avalanche
Published in DiRROS: 01.04.2020; Views: 4128; Downloads: 3249
.pdf Full text (893,89 KB)

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Reconstruction of landslide activity using dendrogeomorphological analysis in the Karavanke mountains in NW Slovenia
Domen Oven, Tom Levanič, Jernej Jež, Milan Kobal, 2019, original scientific article

Abstract: Tree ring eccentricity was used to reconstruct landslide activity in the last 138 years in the Urbas landslide located at Potoška planina in the NW part of the Karavanke Mountains, Slovenia. The research was based on the dendrochronological sampling of Norway spruce (Picea abies (L.) Karst.) in areas of varying landslide intensity. Analysis of a sudden change in the eccentricity index of 82 curved trees concluded that there were 139 growth disturbances and 16 landslide reactivations between 1880 and 2015, with a landslide return period of 8.5 years. Using lidar data, changes in the surface of the digital terrain model (DTM) were compared with changes in the eccentricity index of trees at the same location in the period 2014-2017. On the basis of temporal changes in the eccentricity index and by using spatial interpolation, landslide activity was reconstructed for the period 1943%2015. During this period, landslide intensity increased in the central part of the landslide. Although categorization into seven categories of different stem curvature was proposed, no distinction between categories with respect to their eccentricity index was found.
Keywords: landslide activity, dendrogeomorphology, tree ring eccentricity, eccentricity index, digital terrain model, spatial interpolation
Published in DiRROS: 20.02.2020; Views: 1867; Downloads: 1334
.pdf Full text (9,35 MB)
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Uporaba laserskega skeniranja za vrednotenje poškodovanosti dreves zaradi žledoloma
Aleš Benčina, Milan Kobal, 2019, original scientific article

Abstract: Na območju GGE Snežnik smo ocenili poškodovanost krošenj po žledolomu iz leta 2014. Območje smo posneli z laserskim skeniranjem novembra 2013 in aprila 2014. Lidarske podatke smo obdelali v programih ArcMap in CloudCompare. V raziskavo smo vključili 111 dreves, od tega 65 navadnih jelk (Abies alba Mill.) in 46 navadnih bukev (Fagus sylvatica L.). S programom CloudCompare smo izračunali razdalje med točkami, ki so si bile najbližje med oblakoma točk iz let 2013 in 2014. Tako smo ugotovili razdalje poškodovanosti, s katerimi smo ugotovili naslednje: bukve so bile statistično značilno bolj poškodovane kot jelke (p < 0,05). Preverili in statistično potrdili smo povezavo med višino drevesa in poškodbami krošnje (p < 0,05) ter dolžino krošnje in poškodbami krošnje (p < 0,05). Vpliva sestojnega sklepa na poškodovanost krošenj po žledu nismo uspeli statistično značilno potrditi (p > 0,05).
Keywords: lasersko skeniranje, žled, poškodovanost gozdov, geoinformatika, daljinsko zaznavanje
Published in DiRROS: 17.06.2019; Views: 2846; Downloads: 730
.pdf Full text (384,45 KB)

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Daljnovodne preseke v gozdnem prostoru
Nataša Buser, Milan Kobal, 2019, original scientific article

Abstract: Prispevek obravnava vidnost daljnovoda v prostoru in v nadaljevanju prikazuje možnost prilagajanja poseka na koridorju daljnovoda, pri čemer so avtorji upoštevali reliefne razmere in različne simulirane višine drevja (od 5 do 35 m). Kot primer je bil izbran odsek obstoječega 220 kV daljnovoda med Hrušico in Postojnskim poljem (skupna dolžina 11.024 m). Vidnosti so bile izračunane znotraj radija moteče razdalje (4.100 m). Daljnovodni stebri (skupaj 30) so bili vidni s 33 % površine, različno široke preseke (pri določenih višinah drevja 15, 25 in 35 m) so bile v povprečju vidne s 30,3 % območja. Dolžina gozdnega roba in površina potrebnega poseka sta bili največji pri najvišjih simuliranih višinah drevja. Razlike v površini poseka so se večale linearno, medtem ko so se razlike v dolžini gozdnega robu eksponentno zmanjševale z večjimi simuliranimi višinami drevja.
Keywords: daljnovodna preseka, vidnost, gozdni rob, krajina, geoinformatika, daljinsko zaznavanje
Published in DiRROS: 20.03.2019; Views: 2980; Downloads: 794
.pdf Full text (317,46 KB)

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Analiza hudourniških in erozijskih procesov z uporabo posnetkov brezpilotnih letalnikov
Milan Kobal, 2019, original scientific article

Abstract: Brezpilotni letalniki postajajo vedno pogosteje uporabljena tehnologija pri spremljanju hudourniških in erozijskih procesov. V članku je podrobneje predstavljena uporabnost brezpilotnih letalnikov za spremljanje hudourniških (območje Suhega potoka v Zadnji Trenti) in erozijskih procesov (skalni podor nad vasjo Belca). Snemanje smo izvedli z letalnikoma DJI Phantom 3 Pro ter DJI Mavic Air, talne kontrolne točke zajeli s sprejemnikom GNSS Leica Zeno 20 & Leica GG04 Smart Antenna, oblake točk pa izdelali v programu Pix4Dmapper. Točnost georferenciranja oblakov točk je manjša od 0,016 m (RMSE). Nadmorska višina struge Suhega Potoka v Zadnji Trenti se je glede na leto 2014 zvišala na površini 1,01 ha (v povprečju za 0,31 m) ter glede na leto 2014 znižala na površini 1,31 ha (v povprečju za 0,39 m). Na podlagi razlike digitalnega modela reliefa pred podorom (DMR_0) ter po podoru (DMR_1) sklepamo, da se je na območju skalnega podora Belca skupno porušilo 27068,0 m3 skalnega materiala, in sicer na prvem mestu 18144 m3 in na drugem 8924,2 m3 . Upoštevali smo le območja, kjer se je nadmorska višina znižala za več kot 0,1 m. Uporaba brezpilotnih letalnikov tako v raziskovalnem delu na področju proučevanja hudourniških in erozijskih procesov kot tudi pri ukrepanju in reševanju v primeru različnih naravnih nesreč postaja vedno bolj množična.
Keywords: brezpilotni letalniki, slikovno ujemanje, digitalni model reliefa, hudourniki, erozija
Published in DiRROS: 21.02.2019; Views: 3232; Downloads: 767
.pdf Full text (437,93 KB)

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