1. Can we use dendrogeomorphology for the spatial and temporal analysis of less intensive mass movement processes?: Acase study of three debris flows in NW and W SloveniaMatevž Konjar, Tom Levanič, Thomas Andrew Nagel, Milan Kobal, 2021, izvirni znanstveni članek Povzetek: Debris flows can transport large amounts of material and therefore present a significant threat to infrastructure and human life. In this research, we used tree-ring width analyses to quantify the response of trees to three debris flow events in NW Slovenia (Javoršček, Srpenica) and W Slovenia (Nikova) for which we know the time of origin. We attempted to date these and similar tree responses in the past and compared the patterns between different tree species. Altogether, we sampled 147 trees across a range of tree species (Fagus sylvatica, Pinus sylvestris, Fraxinus excelsior, Fraxinus ornus, Acer pseudoplatanus, Picea abies, Juglans regia, Acer campestre, Tilia cordata and Ostrya carpinifolia), including reference trees that were outside the debris flow fan. For 91 trees, we constructed tree-ring chronologies and used pointer-year analysis to identify years that had abnormal growth. For the remaining trees (mostly Ostrya carpinifolia, Tilia cordata and Acer pseudoplatanus), we either could not accurately distinguish tree rings or two samples from a single tree showed significantly different growth patterns. The growth patterns of Fagus sylvatica and Picea abies following debris flow events showed a weak response at the Javoršček site and no clear responses at the other two sites. Tree species responded similarly at the same locations. Due to the lack of a clear response pattern, we were not able to reconstruct past debris flows.
Ključne besede: debris flows, tree rings, dendrogeomorphology, slope processes
Objavljeno v DiRROS: 30.03.2021; Ogledov: 3931; Prenosov: 2261
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2. Growth-limiting factors and climate response variability in Norway spruce (Picea abies L.) along an elevation and precipitation gradients in SloveniaJernej Jevšenak, Ivan Tychkov, Jožica Gričar, Tom Levanič, Jan Tumajer, Peter Prislan, Domen Arnič, Margarita Popkova, Vladimir V. Shishov, 2020, izvirni znanstveni članek Povzetek: Norway spruce (Picea abies L.) is among the most sensitive coniferous species to ongoing climate change. However, previous studies on its growth response to increasing temperatures have yielded contrasting results (from stimulation to suppression), suggesting highly site-specific responses. Here, we present the first study that applies two independent approaches, i.e. the nonlinear, process-based Vaganov-Shashkin (VS) model and linear daily response functions. Data were collected at twelve sites in Slovenia differing in climate regimes and ranging elevation between 170 and 1300 m a.s.l. VS model results revealed that drier Norway spruce sites at lower elevations are mostly moisture limited, while moist high-elevation sites are generally more temperature limited. Daily response functions match well the pattern of growth-limiting factors from the VS model and further explain the effect of climate on radial growth: prevailing growth-limiting factors correspond to the climate variable with higher correlations. Radial growth correlates negatively with rising summer temperature and positively with higher spring precipitation. The opposite response was observed for the wettest site at the highest elevation, which positively reacts to increased summer temperature and will most likely benefit from a warming climate. For all other sites, the future radial growth of Norway spruce largely depends on the balance between spring precipitation and summer temperature.
Ključne besede: Vaganov-Shashkin model, climate-growth correlations, tree rings, process-based modelling, dendroTools, dendroclimatology
Objavljeno v DiRROS: 21.10.2020; Ogledov: 1223; Prenosov: 977
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3. 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, izvirni znanstveni članek Povzetek: 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.
Ključne besede: rockfall, natural hazards, dendrogeomorphology, tree rings, stem scars, recurrence interval
Objavljeno v DiRROS: 01.04.2020; Ogledov: 3937; Prenosov: 2999
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4. Daily climate data reveal stronger climate-growth relationships for an extended European tree-ring networkJernej Jevšenak, 2019, izvirni znanstveni članek Povzetek: An extended European tree-ring network was compiled from various sources of tree-ring data from Europe, northern Africa and western Asia. A total of 1860 tree-ring chronologies were used to compare correlation coefficients calculated with aggregated day-wise and month-wise mean temperature, sums of precipitation and standardised precipitation-evapotranspiration index (SPEI). For the daily approach, climate data were aggregated over periods ranging from 21 to 365 days. Absolute correlations calculated with day-wise aggregated climate data were on average higher by 0.060 (temperature data), 0.076 (precipitation data) and 0.075 (SPEI data). Bootstrapped correlations are computationally expensive and were therefore calculated on a 69.4% subset of the data. Bootstrapped correlations indicated statistically significant differences between the daily and monthly approach in approximately 1% of examples. A comparison of time windows used for calculations of correlations revealed slightly later onset and earlier ending day of the year for the daily approach, while the largest differences between the two approaches arise from window lengths: Correlations calculated with day-wise aggregated climate data were calculated using fewer days than the monthly approach. Differences in the onset and ending dates of periods for the daily and monthly approaches were greater for precipitation and SPEI data than for temperature data.
Ključne besede: tree rings, dendroclimatology, tree-ring network, daily climate data, climate-growth relationships, dendroTools
Objavljeno v DiRROS: 21.08.2019; Ogledov: 2243; Prenosov: 1028
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