Diameter growth reaction of Scots pine (Pinus sylvestris L.) to climate situations in the Strážnice region

Characteristic feature of the Czech forests is relatively simple species composition with prevailing Norway spruce (Picea abies Karst.) - 55% and Scots pine (Pinus sylvestris L.) - 18%. Scots pine stands occupy mainly low land sandy sites with higher mean temperature and lower sum of precipitation. Analysing the climatic time series (1970 - 2002) from Southern Moravia region (Czech Hydrometeorological Institute CHMI - station Strážnice, 176 m a. s. 1.), it was found that the difference between the highest and the lowest mean annual temperature may achieve even 2.8 degree C (e.g. 7.8 degree C in 1985 and 10.6 degree C in 1994 and 2000) and the differences in annual sum of precipitation may represent 324 mm (e.g. 368 mm in 1992 and 692 mm in 1985, Fig. l). It means that contemporary forests had to cope with various climatic situations including those with elevated temperature and deficient precipitation. Objective of the study was to find out the answer to following question: What was diameter growth response of contemporary Scots pine stands to mentioned climate situations with respect to cases characterised by interaction of precipitation deficiency and high temperature? The data from non thinned (control) variants of three experimental thinning series was used for the evaluation of growth response of pine stands to climate situations. Experiments were established by the uniform method in 1962 (age of the stands 25 - 38 years) in the stands without thinning on nutrient-poor localities in oak forest vegetation zone (Pineto - Quercetum oligotrophicumarenosum) at an elevation of 190 - 207 m. Diameter at breast height of all trees is measured annually or in five-year-period on marked places with precision of 1 mm. Group of dominant trees was selected from control variant (0.25 ha) of each experiment, e. g. 20 dominant individuals with the largest diameter in the age of establishment. Increment cores were taken from these trees and age-related trends in diameter increment are removed by fitting of growth function (equation by Korf) and the data are checked and compared visually. Comparing climatological data (monthly average temperature and total precipitation) are taken from stations of CHMI - station Strážnice. Besides the data for each month, three climatic factors (F1, F2 and F3) and two periods were determined (vegetation and spring). Diameter growth responses were analysed in connection with long-term deviations of climatic factors (F1, F2 and F3), average temperature and total precipitation for vegetation and spring period and for individual month. Statistical analyses (significance tests of correlation coefficients, box and dot plots, etc.) were performed on the level of a = 0.05 using the statistical software package UNISTAT (version 5.1).