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Iskalni niz: "ključne besede" (climate reconstruction) .

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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: 1258; Prenosov: 429
.pdf Celotno besedilo (1,19 MB)

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: 189; Prenosov: 132
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