DIGITALNA ARHIVA ŠUMARSKOG LISTA
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| ŠUMARSKI LIST 7-8/2022 str. 48 <-- 48 --> PDF |
standing trees, provided that two increment cores are taken from each tree (Fritts 1976; Accetto 1977; Levanič 1996). At each site, three additional trees were drilled to serve as a substitute in case samples got damaged in the measurement preparation or sampled trees had heart rot or atypical growth, or for some other reasons that could hinder cross-dating (missing or false tree rings). Having been prepared in the laboratory, the cores were scanned using a high-performance scanner: the Epson Perfection V30 Photo Scanner. Each increment core that was used to make the chronology passed through the tree center, which provided accurate computation of the tree age. The tree-ring width (TRW) was measured using the CooRecorder 7.6 and CDendro 7.6 software (available at http://www.cybis.se/forfun/dendro/). Chronology development – Razvoj kronologije Site chronologies of Scots and Austrian pine were developed based on data obtained from tree-ring width measurements. This three-step procedure includes cross-dating, data standardization, and master chronology development. The accuracy of annual tree-ring dating, i.e. determining the calendar year in which it was formed, was verified using the cross-dating procedure. Cross-dating was done by using visual on-screen comparisons and statistical analysis. Visual on-screen techniques in the CDendro program and statistical methods of the Cofecha specialized software (Holmes 1983; Grissino-Mayer 2001) were used. According to Grissino-Mayer (2001), Cofecha software adds a high degree of confidence that tree-ring samples have been measured accurately and cross-dated correctly. The standardization of tree-ring width time series essentially represents the elimination of the so-called age-related trend. It was performed using Arstan software (AutoRegressive STANdardization; MRWE Application Framework © 1997–2004 Absoft Corporation) and cubic smoothing spline (Cook and Peters 1981; Cook 1985; Cook and Holmes 1997). The processing in the Arstan program results in three versions of the chronology (tree-ring index): standard, residual, arstan, and a comprehensive overview of the results of statistical analysis. For the comparison with climatic parameters, the arstan chronology was used because the Arstan chronology has the best climate signal. To assess the possibility of combining the obtained site chronologies to develop master chronologies of Scots and Austrian pine in the Zavidovići-Teslić area, t-values (tBP) according to Baillie and Pilcher (1973) was calculated. The coefficient of agreement (Gleichläufigkeit) – GLK (Huber 1943; Eckstein and Bauch 1969) was also used. It measures the degree of overlap between two chronologies in the observed interval. Meteorological data – Meteorološki podaci Meteorological data (mean monthly temperatures and precipitation) used to analyze the impact of climatic parameters on radial growth was measured at the nearest meteorological station (Doboj, 146 m a.s.l, Longitude 44°44’ and Latitude 18°06’). The climate in the region is generally characterised by strong temperature seasonality with a maximum in July and August. The maximum sum of precipitation occurs in June and the minimum in January and February. The mean annual air temperature is around 10.9°C and the mean annual sum of precipitation is about 932 mm, with fluctuations ranging from 502 to 1495 mm in the period from 1952 to 2014. The temperature has had an increasing trend in recent decades, while precipitation shows an increase in the variability of the annual sum of precipitation (Figure 2). The cumulative effect of temperature and precipitation on radial growth was analysed using the Forestry Aridity Index (FAI) and Standardized Precipitation Evapotranspiration Index (SPEI). Higher Forestry Aridity Index values |