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Iskalni niz: "ključne besede" (tree rings) .

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Daily climate data reveal stronger climate-growth relationships for an extended European tree-ring network
Jernej Jevšenak, 2019

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
DiRROS - Objavljeno: 21.08.2019; Ogledov: 544; Prenosov: 270
URL Celotno besedilo (0,00 KB)
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Forest resilience to drought varies across biomes
Antonio Gazol, Jesus Julio Camarero, Sergio M. Vicente-Serrano, Raúl Sánchez-Salguero, Emilia Gutiérrez, Martin De Luis, Gabriel Sangüesa-Barreda, Klemen Novak, Vicente Rozas, Pedro A. Tíscar, 2018

Povzetek: Forecasted increase drought frequency and severity may drive worldwide declines in forest productivity. Species-level responses to a drier world are likely to be influenced by their functional traits. Here, we analyse forest resilience to drought using an extensive network of tree-ring width data and satellite imagery. We compiled proxies of forest growth and productivity (TRWi, absolutely dated ring-width indices; NDVI, Normalized Difference Vegetation Index) for 11 tree species and 502 forests in Spain corresponding to Mediterranean, temperate, and continental biomes. Four different components of forest resilience to drought were calculated based on TRWi and NDVI data before, during, and after four major droughts (1986, 1994-1995, 1999, and 2005), and pointed out that TRWi data were more sensitive metrics of forest resilience to drought than NDVI data. Resilience was related to both drought severity and forest composition. Evergreen gymnosperms dominating semi-arid Mediterranean forests showed the lowest resistance to drought, but higher recovery than deciduous angiosperms dominating humid temperate forests. Moreover, semi-arid gymnosperm forests presented a negative temporal trend in the resistance to drought, but this pattern was absent in continental and temperate forests. Although gymnosperms in dry Mediterranean forests showed a faster recovery after drought, their recovery potential could be constrained if droughts become more frequent. Conversely, angiosperms and gymnosperms inhabiting temperate and continental sites might have problems to recover after more intense droughts since they resist drought but are less able to recover afterwards.
Ključne besede: dendroecology, drought stress, forest growth, resilience index, tree-rings
DiRROS - Objavljeno: 20.02.2020; Ogledov: 174; Prenosov: 141
URL Celotno besedilo (0,00 KB)

Streamflow as an ecological factor influencing radial growth of European ash (Fraxinus excelsior (L.))
M. Koprowski, Bernard Okoński, Jožica Gričar, Radosław Puchałka, 2018

Povzetek: The aim of our study was to find the hydrological, precipitation and temperature signal in tree rings and selected cell parameters of European ash (Fraxinus excelsior L.) in the floodplain forest of the Warta River. A total of 30 samples were taken at breast height, using a Pressler borer, from 15 trees (2 samples per tree) during the 2012 vegetation season. We measured the tree-ring widths, built the chronology, selected the tree that was the best correlated with the rest, and used both samples from this tree for cell analysis. For earlywood vessels, average and total density, as well as the percentage of water conductive area were calculated for the years 1950%2011. We found that high water levels during September to January of the previous year positively influence tree growth. This finding could be associated with the accumulation of nutrients, like nitrogen, in the floodplain soil, which are then used at the beginning of the growing season or earlier, when the trees transition from the true dormancy phase to relative dormancy. Temperature at the end of winter and early spring did not play a big role in tree-ring width, whereas low temperature in February negatively affected the number and the area of the earlywood cells. In addition, precipitation during the growing season, especially in June, had a positive effect on ring width. To summarize, our research showed that in the case of European ash from lowland flood-areas, river flows had a large influence on growth. Precipitation and air temperature, which both shape the river regime and directly supply forest ecosystems with water, were also important for tree growth and tree-ring structure.
Ključne besede: tree rings, dendroecology, dendrohydrology, wood anatomy, earlywood vessels, maximum river flow
DiRROS - Objavljeno: 20.02.2020; Ogledov: 166; Prenosov: 83
URL Celotno besedilo (0,00 KB)

The impact of adverse weather and climate on the width of European beech (Fagus sylvatica L.) tree rings in Southeastern Europe
Stefan Stjepanović, Bratislav Matović, Dejan Stojanović, Branislava Lalić, Tom Levanič, Saša Orlović, Marko Gutalj, 2018

Povzetek: European beech (Fagus sylvatica L.) is the most important deciduous tree species in Europe. According to different climate scenarios, there is a relatively high probability of a massive decline in and loss of beech forests in southern Europe and in the southern part of central Europe. Thus, the authors of this study explored the dynamics of tree diameter increments and the influence of extremely dry years on the width of tree rings. This study used dendroecological methods to analyze the growth and diameter increments of European beech trees at locations in Serbia and the Republic of Srpska. The sampling was conducted along the vertical distribution of beech forests, at five sites at the lower limit of the distribution, at five optimal sites of the distribution, and at five sites at the upper limit of the distribution. Long-term analyses indicate that dry conditions during a growing season can reduce tree-ring width, but a reduction in tree growth can be expected as a result of more than one season of unfavorable conditions. Low temperatures in autumn and winter and prolonged winters can strongly affect upcoming vegetation and reduce tree development even under normal thermal conditions during a growing season.
Ključne besede: European beech, climate change, drought, air temperature, precipitation, tree rings, dendrochronology, Fagus sylvatica L.
DiRROS - Objavljeno: 20.02.2020; Ogledov: 228; Prenosov: 137
URL Celotno besedilo (0,00 KB)

Xylogenesis reveals the genesis and ecological signal of IADFs in Pinus pinea L. and Arbutus unedo L.
Angela Balzano, Katarina Čufar, Giovanna Battipaglia, Maks Merela, Peter Prislan, Giovanna Aronne, Veronica De Micco, 2018

Povzetek: Background and Aims: Mediterranean trees have patterns of cambial activity with one or more pauses per year, leading to intra-annual density fluctuations (IADFs) in tree rings. We analysed xylogenesis (January 2015 - January 2016) in Pinus pinea L. and Arbutus unedo L., co-occurring at a site on Mt. Vesuvius (southern Italy), to identify the cambial productivity and timing of IADF formation. Methods: Dendrochronological methods and quantitative wood anatomy were applied and enabled IADF identification and classification. Key Results: We showed that cambium in P. pinea was productive throughout the calendar year. From January to March 2015, post-cambial (enlarging) earlywood-like tracheids were observed, which were similar to transition tracheids. The beginning of the tree ring was therefore not marked by a sharp boundary between latewood of the previous year and the new xylem produced. True earlywood tracheids were formed in April. L-IADFs were formed in autumn, with earlywood-like cells in latewood. In A. unedo, a double pause in cell production was observed, in summer and winter, leading to L-IADFs in autumn as well. Moreover, the formation of more than one IADF was observed in A. unedo.
Ključne besede: kambijeva aktivnost, funkcionalni znaki v lesu, gostotne variacije v branikah, Pinus pinea L., Arbutus unedo L., ksilogeneza, branike, cambial activity, functional wood traits, intra-annual density fluctuations, xylogenesis, tree rings
DiRROS - Objavljeno: 20.02.2020; Ogledov: 214; Prenosov: 164
URL Celotno besedilo (0,00 KB)

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

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
DiRROS - Objavljeno: 01.04.2020; Ogledov: 179; Prenosov: 471
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