Rola wskaźnika NAO w kształtowaniu przyrostów rocznych sosny zwyczajnej

The role of NAO index in formation of Scots pine tree ring width

Summary: The study presents the results of dendroclimatological research on Scots pine (Pinus sylvestris L.) from NW Poland. The goal of the research was to determine the influence of the seasonal indices of the North Atlantic Oscillation on the width of annual growth rings in Scots pine. The sampling was carried out with Pressler increment borers. Measurements of tree-ring widths with an accuracy of ą0.01 mm were performed with dendrometric measurement equipment. Statistical treatment and graphical presentation of the data were carried out using the TREE-RINGS (Krawczyk 1995; Krawczyk, Krąpiec 1995), DendroGraph (Walanus 2001), and DPL (Holmes 1983, 1994) computer applications. Analyses of signature years were performed with the TCS (Walanus 2002) for chronology application. The signature years were determined from a minimum of 10 trees, at a minimum convergence threshold of 90%. Statistical analysis of the influence of the NAO index on tree growth was made on indexed averages in order to eliminate non-climatic signals (age trend and autocorrelation). Therefore, the measured chronologies were replaced by the residual ones (RES) in the ARSTAN application (from the DPL set, Holmes 1994). In the response function analysis the influence of climatic factors on tree-ring patterns was examined for 16-month intervals (from June of the previous year to September of the year being analysed) in the periods 1831-1880, 1881-1930, 1931-1980, 1981-2000 and 1831-2000 (Table 1). Field work was performed during the years 1997-2002 in forest areas under the control of the Regional Direction of National Forests in Szczecin. The forest areas include nature reserves as well an area in the Wolin National Park. Altogether 16 research plots were established for the species Pinus sylvestris L. (Scots pine) and core samples, the basic research materials, were taken from 263 trees. Comparisons of statistical parameters permitted the selection of the 86 most convergent sequences which were used for the construction of the regional chronology for the species Pinus sylvestris L., labelled PZsosna. The 226-year long standard covers the period 1777-2002.The Scots pine chronology clearly responds to the seasonal variability in the NAO, especially variation during the winter period (January-March) (Fig. 1). In most cases where a negative signature year occurred the determining factors were the NAO indices for winter (January and February) and the beginning of spring (March). Low values in these months resulted in the formation of narrower growth rings in the subsequent vegetation season. Positive signature years were generally associated with mild winters followed by early and warm springs (represented by positive values of the NAO index). Results of the dendroclimatological analysis - response function, for the species Pinus sylvestris L. (relationships between tree-ring widths and NAO index) are presented in Table 1. Formation of annual growth rings is mostly dependent on the NAO indices for January, February and March (positive correlation and multiple regression coefficients) and May (negative values). The plot of the average NAO index for the months January-February-March against the widths of annual rings of the species Pinus sylvestris L. from Western Pomerania, together with results of dendroclimatological analyses carried out, revealed that narrow rings corresponded to low values of NAO index and wide rings correspond to positive values of the mean NAO index (January-March) in the interval analysed (Fig. 2).Scots pine chronology from the northern part of Europe (forest-limit region) correlates with the summertime NAO index. The pine tree ring width from the southern part of Finland and Sweden corresponds with the wintertime NAO index (Lindholm et al. 2001). Cook reconstructed the December to March NAO index based on tree ring width records from North America and Europe (Cullen et al. 2001, Cook et al. 1998).

Słowa kluczowe: przyrosty roczne drzew, sosna zwyczajna (Pinus sylvestris L.), wskaźnik NAO, Pomorze Zachodnie

Słowa kluczowe (w języku angielskim): tree ring width, Scots pine (Pinus sylvestris L.), NAO index, Western Pomerania

Piotrowicz K., Twardosz R., 2007, Wahania klimatu w różnych skalach przestrzennych i czasowych, IGiGP UJ, Kraków, s. 323-330.

Instytut Geografii i Gospodarki Przestrzennej UJ

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