Retrospective evaluation of the response of montane forest ecosystems to multiple stress

Montane forests have been under long-term synergistic chronic effects of na tural and anthropogenic stress impacts, and imposed from time to time to ac ute climatic and pollution stress events. Crown structure transformation (f ormation of secondary shoots of different orders in successive series on da maged and/or defoliated branches) is a very sensitive indicator of longterm tree damage processes (30-40 years back), and of the subsequent regenerati ve processes. Tree crowns on six permanent research plots in the Krkonose M ts were visually investigated and classified into several stages of crown s tructure transformation. One or more trees from the most frequent stages we re selected for investigation of the branch structure transformation. Set o f indicators, enabling to estimate stress response history of trees at bran ch, tree, and stand levels, was proposed. Rate of secondary shoot formation , which compensates a defoliation of primary shoots, indicates overcharging of "stress exceedance starting level". "Significant harmful effect time" c an be detected by estimation of the time of termination of annual wood prod uction of primary shoots, In addition, trends of probable subsequent develo pment of trees investigated were estimated at branch, tree, and stand level s. The proposed approach outlined in this paper could be used for the inves tigation of structural and functional changes of various ecosystems under m ultiple stress impacts.