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ISOTOPE MONITORING OF FOREST ECOSYSTEMS

Galina Simonova, Yuriy Volkov, Anna Markelova, Daria Kalashnikova

Abstract

In this article we consider the opportunity of the use of tree-ring ?13C carbon isotope composition records for detecting and recognizing changes in forest ecosystems in the south of the West Siberian Plain where the growth conditions for conifer trees are generally optimal. Trees grow in the closed stands. The wood of Larix sibirica and Pinus sylvestris trees was chosen as object of our research. The values of carbon isotope composition (?13?) were measured in tree ring cellulose and lignin of Larix sibirica and in tree ring cellulose of Pinus sylvestris with the elemental analysis by mass spectrometry complex on the basis of the isotope mass spectrometer DELTA V Advantage (Thermo Fisher Scientific/USA-Germany. Thus, three tree-ring ?13C records were obtained. The first two records cover time region of 1971пїЅ2010 years, the last one corresponds to 1992пїЅ2010. All records vary synchronously on the common (1992пїЅ2010) time interval. Consequently, they contain a common signal which is likely to have information about the climatic conditions. The distant between localities of the wood sampling is about 70 km. Despite the very short common period the correlation coefficients between the ?13C records and meteorological data of vegetation period such as the air temperature, the amount of precipitation and the relative humidity appeared to be significant with reliable probability of 0.95. However, a careful study of both the chronologies of Larix sibirica showed an abrupt change in the ?13C values level after 1990. The similar changes have not been found in the meteorological data. Consequently, the considered shift might be caused by some random event. Having studied the restored history of the tree stand development we have come to the conclusion that it was most likely a selective felling of trees. This event divided the whole investigated period of 1971пїЅ2010 into two subperiods during which the ?13C records correlate differently with meteorological parameters. According to the values of correlation coefficients in the second period the correlations of the tree ring ?13C records of Larix sibirica with temperature and precipitation were stronger, and with relative humidity пїЅ weaker in comparison with the first period. We assume that this change was caused by a decrease in the competition between trees for soil moisture after selective felling. Thus, despite the optimal tree growth conditions tree-ring ?13C records contain a climatic signal and information about disturbances in forest ecosystems that can be detected using isotope monitoring.

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DOI resolver: doi.org/10.5593/sgem2017/32/s14.114

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