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Iskalni niz: "ključne besede" (dendroclimatology) .

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Examination of stable carbon and oxygen isotopic variability in the cellulose and wholewood of Castanea sativa Mill., Fagus sylvatica L., Pinus sylvestris L. and Quercus robur L.
D. McCarroll, G.H.F. Young, N.J. Loader, B. Sladden, 2018

Povzetek: This paper presents results from a comparison of wholewood and cellulose carbon and oxygen isotope ratios for four UK tree species. These species occur within the historic buildings archive as both primary and supplementary construction materials and have been used to reconstruct the climate of the past. New advances in the application of stable isotopes have widened the scope of the isotope approach, but require the time-consuming purification of cellulose. Comparison of the oxygen and carbon isotope signals preserved in the wood and cellulose components confirms and builds upon previous research in this field and provides additional insight into the covariance of these two sample types between species, an
Ključne besede: stable isotopes, tree ring, dendrochronology, dendroclimatology
DiRROS - Objavljeno: 04.02.2019; Ogledov: 1245; Prenosov: 740
.pdf Celotno besedilo (1,63 MB)

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: 603; Prenosov: 288
URL Celotno besedilo (0,00 KB)
Gradivo ima več datotek! Več...

DendroTools : R package for studying linear and nonlinear responses between tree-rings and daily environmental data
Tom Levanič, Jernej Jevšenak

Povzetek: We introduce in this paper the dendroTools R package for studying the statistical relationships between tree-ring parameters and daily environmental data. The core function of the package is daily_response(), which works by sliding a moving window through daily environmental data and calculating statistical metrics with one or more tree ring proxies. Possible metrics are correlation coefficient, coefficient of determination and adjusted coeffi- cient of determination. In addition to linear regression, it is possible to use a nonlinear artificial neural network with the Bayesian regularization training algorithm (brnn). dendroTools provides the opportunity to use daily climate data and robust nonlinear functions for the analysis of climate-growth relationships. Models should thus be better adapted to the real (continuous) growth of trees and should gain in predictive capabilities. The dendroTools R package is freely available in the CRAN repository. The functionality of the package is demonstrated on two examples, one using a mean vessel area (MVA) chronology and one a traditional tree-ring width (TRW).
Ključne besede: dendroclimatology, daily climate data, running window, nonlinear modelling, tree-ring proxies, climate reconstruction
DiRROS - Objavljeno: 16.04.2018; Ogledov: 1313; Prenosov: 463
.pdf Celotno besedilo (1,19 MB)

Green water reconstructed for Rižana watershed, SW Slovenia
Tom Levanič, Urša Vilhar, Simon Poljanšek

Povzetek: In this case study, set in south-west Slovenia, the feasibility of reconstructing green water (the combined amount of evaporated and transpired water in trees and available in the soil) was investigated. In a simplifed scheme, the amounts of green water were calculated as the diference between precipitation and discharge of the Rižana river. Based on the methods of dendroclimatology, the climate signal was tested on black pine (Pinus nigra Arnold) trees growing in the south-western part of the Rižana watershed near the Slovenian sea coast. Results showed that the measured tree-ring parameters of tree-ring width and density are strongly dependent on the amount of green water. The strongest correlation was between available green water in the period May-August and tree-ring width (r=0.61) and latewood width (r=%0.64) (both n=46, p<0.001). The climate signal is signifcant and stable through time, which enabled the reconstruction of green water data into the period before instrumentally measured data. Green water data from the May-August period were extended from 1966 back to 1937 using tree-ring width, and back to 1940 using latewood width. With additional coring of older trees and the extension of existing chronologies, even longer reconstructions could be developed.
Ključne besede: tree-ring width, tree-ring density, dendrochronology, dendroclimatology, reconstruction
DiRROS - Objavljeno: 18.04.2018; Ogledov: 1144; Prenosov: 469
.pdf Celotno besedilo (1003,43 KB)

Stable isotopes reveal climate signal hidden in tree rings of endemic Balkan Pines
Tom Levanič, Jernej Jevšenak, Polona Hafner, 2020

Povzetek: Studies report the good potential of Pinus heldreichii (PIHE) and Pinus peuce (PIPE) for developing long chronologies from living trees and warn that the climate signal is weak in tree-ring widths of PIHE, and particularly PIPE. The goals of the study were to develop long chronologies, and to analyze the climate-growth relationship and potential for long climate reconstructions using tree-ring widths (TRW) and stable carbon isotopes ratios ([delta]13C) in tree rings at the northern edge of species distribution in the eastern part of Montenegro. The PIHE TRW chronology covers the period 1571-2013 (443 years) and the PIPE TRW chronology 1521-2013 (493 years). The temperature signal in PIHE TRW is weak and the precipitation signal is non-existent. PIPE has no climate signal in TRW. Both studied species have very similar [delta]13C chronologies, which allows us to merge isotope chronologies into a single composite [delta]13C Pinus chronology. The composite chronology has a strong signal related to average monthly temperature in June, July, and August and monthly values for cloudiness in July and August, with r > 0.6 and r < -0.6 for individual months, respectively. The climate signal was enhanced when June, July, and August values were merged into seasonal variables. The temporal stability of temperature, precipitation and cloudiness signals is consistent. The spatial extent of the [delta]13C chronology extends over a very large region, including all surrounding countries.
Ključne besede: Pinus heldreichii, Pinus peuce, climate reconstruction, dendrochronology, dendroclimatology, Balkan Peninsula, Bosnian pine, Macedonian pine, Pinus heldreichii H. Christ., Pinus peuce Grisb.
DiRROS - Objavljeno: 20.02.2020; Ogledov: 242; Prenosov: 160
URL Celotno besedilo (0,00 KB)

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