Growth responses to climatic variables of red pine (Pinus resinosa Aiton) and Norway spruce (Picea abies L. Karst) were studied at the Morgan Arboretum, near Montreal, in southern Quebec, Canada (45$ sp circ$ 25$ sp prime$ N, 73$ sp circ$ 57$ sp prime$ W; 15.2 m above sea level). The relationships between climatic variables and basal area growth were examined using linear and quadratic models. Current and previous year's climatic variables were tested separately and in combination using multiple regression models. The best models explained 82% and 85% of the total variance of the growth of Norway spruce and red pine, respectively. The growth of both species was more associated with evapotranspiration than precipitation. The growth of Norway spruce was best explained by the current year's annual evapotranspiration (43%), while the growth of red pine was more related to previous year's August evapotranspiration (33%) at our site. / The JABOWA model was used to predict tree growth in hypothetical climates which could result from global climate changes. Based on literature, five treatments were applied: normal, and increases of 1, 3, 5, and 10$ sp circ$C. Comparison between the last (1983-1992) and next (1993-2002) ten years growth showed no significant differences between species when temperature was normal or increased by 1 and 3$ sp circ$C, but significant differences between species were observed when the temperature was increased by 5$ sp circ$C. Both species declined when the temperature was increased by 10$ sp circ$C. We concluded that Norway spruce is more sensitive to increases in atmospheric temperatures than red pine at our site.

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The Earth's climate system has recently experienced substantial warming which likely impacts temperature-limited communities close to their distribution margins. The alpine treeline ecotone represents upper distributional limit of montane/subalpine forests. This biogeographic boundary relies mainly on decreasing temperature with increasing elevation. Surprisingly the response of treeline ecotone to ongoing warming has varied a lot and the reasons of this variability are poorly understood. The aim of this dissertation thesis is the assessment of growth trends and tree ring response of Norway spruce (Picea abies[L.] Karst.) to climatic oscillations at treelines and montane forests of East-Central Europe. This dissertation deals with both inter-regional and intra-regional (aspect, elevation) variability of tree growth. The presented results are based on an extensive data set of growth curves for almost 1400 trees. All study sites revealed close relationship between tree ring widths and growing season temperatures as well as the temperatures of October preceding to ring formation season. The main site-dependent differences in growth trends and temperature responses were attributed to elevation, the effect of aspect was relatively less significant. At treelines between the Krkonoše Mts. and Nízké Tatry...