South-East European Forestry (Jun 2010)
Growth Response of Silver Fir and Bosnian Pine from Kosovo
Abstract
Background and Purpose: This paper explore the growth-climate relationships in total ring width chronologies of silver fir (Abies alba Mill.) and Bosnian pine (Pinus heldreichii Christ). The objective of this study is to quantify the climate influence on radial growth of both species. The relationships between climate and ring widths were analyzed using extreme growing years (called pointer years), simple correlations and response functions analysis (bootstrapped coefficients). The objectives of this study were: (1) to define the pattern of climatic response of each species, (2) to highlight the influence of local ecological conditions on tree's growth, and (3) to compare the response of silver fir and Bosnian pine to climate. Responses of total ring width to climate were estimated by establishing the mean relationship between growth and climate through simple correlations analysis and bootstrapped response functions. The response to climatic variability was also assessed by analyzing pointer years which correspond to abrupt changes in growth pattern and revealing the tree-growth response to extreme climatic events. For the period 1908-2008 the mean sensitivity (MS) of total ring width chronology for Bosnian pine (0.209) was higher than silver fir (0.169) suggesting that Bosnian pine is more sensitive to climate (pointer years were more frequent in ring width chronology of Bosnian pine than in silver fir ring width chronology). The high values of first-order autocorrelations for Bosnian pine (0.674) indicated a strong dependence of current growth on the previous year’s growth. Pointer years analysis underlined the high sensitivity to spring temperatures and precipitation for both species. Radial growth for both species depends strongly on spring climate variables (temperatures and precipitation) which play a significant role particularly for earlywood production. Material and Methods: We selected 12 silver fir trees and 15 Bosnian pine trees and took two 5 mm cores per tree perpendicular to the slope. Each core was mounted and sanded following standard dendrochronological procedures. Annual radial growth was measured with a measuring system LINTAB (Rinntech-Germany) where tree-ring widths were recorded using TSAPWin 0.55 software. Each tree-ring width series was crossdated using visual comparisons and statistical parameters like: Cross Date Index-CDI (Schmidt 1987), an index of synchronization estimated by TSAPWin derived from GLK% and t value (Baillie and Pilcher 1973). The value of CDI> 10 (Rinntech 2003) were considered as significant. The ARSTAN software was used to remove age trends in the ring width data and build site chronology. Indices were calculated as ratios between the actual and fitted values. Response from both species to climate was correctly shown by pointer years analysis, Pearson’s correlation coefficients and DENDROCLIM (2002) software. Results and Conclusion: We compiled for each specie a mean chronology of radial growth with good replication. The chronology length of Silver fir is 64 years with mean tree-ring width 3.59 mm (0.506), while the chronology length of Bosnian pine is 104 years with mean tree-ring width 2.44 mm (± 0.482). The Bosnian pine chronology was more sensitive than silver fir chronology (sensitivity 0.209 >0.169). Response of both species to climate was good. That was verified from pointer years analysis, Simple Pearson’s correlation coefficients and DENDROCLIM (2002) software. Pointer year analysis showed that spring temperatures and precipitation are the most important factors that enhance radial growth for both species. The pointer years 1953 and 1955 appear to be the most geographically extended pointer years throughout of Europe. The negative pointer year 1953 was identified in growth of silver fir by Serre Bachet 1986, and positive pointer year 1955 was also observed for silver fir in France. Both species have reacted strongly to several pointer years but bosnian pine was more affected and more sensitive to climate than silver fir. For A. alba, high temperatures and plenty rainfalls during the first part of growing season are the keys for production of earlywood). The response of Bosnian pine growth to climate was quite different than response of silver fir. Response functions analysis showed that precipitation during September is important for latewood production (growing season ends on October). While low temperatures during winter (January) and especially frosts cause substantial growth reduction, delaying the growth starting during spring. Earlier studies has shown that photosynthesis is possible for A. alba in winter, where high temperatures could play an important role in improving carbohydrate storage and growth at following year. For species grown under a Mediterranean climate high temperatures and low precipitation during growing season may cause water stress, which is the main limiting factor for tree growth. Although the drying season lasts in the study area for 2 months we did not note any sign of defoliation or needle yellowing in standing trees.
