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Dendroclimatological Analysis of Wild Pear Pyrus Pyraster (L.) Burgsd. From Biedrusko Military Area (West Poland) — Preliminary Study

Cedro A., Antkowiak W.

Geochronometria

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2016

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Vol. 43, no. 1

18--23

EN

European wild pear (Pyrus pyraster, syn. Pyrus communis subsp. pyraster L.) is widely distributed in Europe, but rarely studied by dendrochronologists. This preliminary study was aimed to assess the age and effect of climate on tree-ring width in the largest Polish population of P. pyraster, in Biedrusko military area (western Poland). On the basis of samples from 21 trees, a chronology (BIE) was constructed, covering 45 years (1963–2007). Mean tree-ring width in the studied trees is 1.92 mm. The performed analyses (pointer years, correlations, and response function) indicate that tree-ring width is strongly dependent on weather conditions in the year preceding formation of the tree-ring. Annual rings of pear trees were wide after cold and rainy previous summer and after rainy previous October, while in the current year, ring width was affected by insolation in February and temperature in August (positive correlations) and precipitation in May (negative correlation). The low similarity of the ring-width pattern and effect of climate on tree-ring width between this population and a wild pear population from the Bielinek Reserve, located 200 km away, indicate that tree-ring width in this species is strongly dependent on habitat and there is a need to continue dendrochronological analyses.

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Assessing the sensitivity of riparian algarrobo dulce (Prosopis flexuosa DC) radial growth to hydrological changes

Alejandro Roig F., Piraino S.

Geochronometria

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2016

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Vol. 43, no. 1

1--8

EN

Ecotones, as for example riparian zones, have long interested ecologists, due to their potential role in generating species biodiversity and evolutionary novelty, as well as their sensitivity to environmental changes. Along riparian areas, vegetation is recognized for its ecological importance in several ecosystemic processes. In the Central Monte Desert (central-west Argentina), Prosopis flexuosa grows in territories characterized by a permanent access to water reservoirs, e.g. along riverbanks, where the species forms the classic gallery forests. Despite the ecosystemic role of the different Prosopis species distributed in arid lands, thus far no analysis has been conducted regarding the relation between their radial growth and hydrological changes, namely streamflow variability, in riparian settings. To fill this gap of knowledge, we performed a dendrochronological analysis considering several riparian P. flexuosa trees differing in their spatial position in relation to the riverbank. Pointer years, correlation function, and regression analyses show differences in the dendrohydrological signal of the studied species, probably function of tree distance from the river. In this sense, radial growth of trees distributed near the riverbank is tightly coupled to spring-summer (September to March) streamflow variability, whereas for farthest trees the ring development is driven by a combination of winter and spring river discharge and late-summer precipitation amount. The presented results demonstrate the potentiality of P. flexuosa, and in a broader sense of the Prosopis genus, in dendrohydrological studies.

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Chronology development and climate response analysis of Schrenk spruce (Picea schrenkiana) tree-ring parameters in the Urumqi River Basin, China

Chen F., Yuan Y, Wei W., Yu S., Li Y., Zhang R., Zhang T., Shang H.

Geochronometria

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2010

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Vol. 36

17-22

EN

Seven different tree-ring parameters (total tree-ring width, earlywood width, latewood width, maximum latewood density, minimum earlywood density, average earlywood density, and average latewood density) were obtained from Schrenk spruce in the Urumqi River Basin, China. The chronologies were analyzed individually and then compared with each other. The relationships between the different tree-ring parameters and climate data (Daxigou) are also presented. Earlywoodrelated parameters (earlywood width, minimum density, and earlywood density) were more sensitive to climate than those of latewood. Temperature (July) was found to be the most strongly related to the earlywood density. Based on the results of climate response analysis, the potential of tree-ring chronologies from this species to provide climate reconstructions in the Urumqi River Basin has been established. This study demonstrates that the use of tree-ring density data can increase the climate information obtained from tree-ring and should lead to improved paleoclimate reconstructions in Central Asian.

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Nonlinear methods of analysis of data with gaps

Dergachev V. A., Makarenko N. G., Karimova L. N., Danilkina E. B.

Geochronometria

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2001

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Vol. 20

45-50

EN

Information on most of natural phenomena can be obtained from time series of direct and proxy data. The analysis of time series generated by natural dynamic systems is a key element in interpreting geophysical and climatic information. Unfortunately, most of available time series have gaps. When there are many gaps with irregular distribution, we do not have any statistical tools for repairing the data. We suggest some approach to solve this problem. It is based on modeling the missing data by small-dimensional manifolds and neural network technologies. In this approach we assume that data under consideration are a set of n-dimensional vectors, which are produced by dynamical system. These vectors model n-dimensional attractor in embedding space. Gaps in the vectors are represented as a linear manifold L of some dimension. The method idea is to model L by another small-dimensional manifold, e.g. a curve. Neural networks are used to find this manifold. We verify the method on real time series data: sunspot numbers, the radiocarbon content in tree rings, the 10Be in ice cores, the width of tree rings and so on.