关键词: 林线, 岳桦和长白落叶松, 种群动态, 生长形态

Abstract:

The aim of this article is to understand the different responses between Laris olgensis and Betula ermanii to environment adaptability on north slopes treeline of the Changbai Mountains. The alpine treeline is regarded as highly sensitive and a potential indicator of environmental change and it has thus become one of the hotspots of environmental change research. Most researches on treeline dynamics have been conducted at a population scale, and there have been comparatively few studies of treeline dynamics at multi-population. In this study, treeline dynamics were analyzed at two populations in the Changbai Mountains by examining the change in relationship between two population’s dynamics and the environment. The treeline of the northern slope of the Changbai Mountains was selected as the study area. Data source was obtained by field investigation and tree-ring analysis. The altitude differences of three growth forms (general tree, flag tree and cushion) of Laris olgensis were revealed by half-peak width, mean ± standard deviation, and One-way ANOVA. DBH (diameter at breast height) of each tree (Laris olgensis and Betula ermanii) was measured by measuring tape (precision: 0.1 cm) and 142 cores were taken from the living trees in plots. The ages of the sampling trees were known using tree-ring and the age-class (DBH) regressions were created to estimate ages of all trees in the plots. The annual stem recruitments of Laris olgensis and Betula ermanii populations were calculated based on field investigations. The difference of growth rates between Laris olgensis and Betula ermanii was understood by assessing differences in the slopes of trend lines and paired-samples T test. The different responses to environmental change between Laris olgensis and Betula ermanii were evaluated using mathematical models. The results showed that cushion growth form of Laris olgensis situated in the highest habitat, followed by flag tree and general tree in the lowest habitat. There were significant differences among three habitats of growth forms of Laris olgensis (p<0.05). The growth velocity of diameter and height growth of Laris olgensis with general growth form was higher than that of Betula ermanii. The difference was not significant between Laris olgensis and Betula ermanii when Laris olgensis changed flag tree. However, Laris olgensis was lower than Betula ermanii when it changed cushion growth form. Population expansions of Laris olgensis and Betula ermanii were very obvious as temperature increase. Expension velocity of Laris olgensis was lower than that of Betula ermanii because it was pressed by Betula ermanii. The growth velocity of all growth forms of Laris olgensis was lower than that of Betula ermanii when tree ages were less than 13 years. Treeline shift was caused mainly by population expansion of Betula ermanii. Laris olgensis was still main accompanying tree specie of Betula ermanii. However, Laris olgensis may become pure forest when Betula ermanii was cut down in quantity.

Key words: treeline, Laris olgensis and Betula ermanii, population dynamic, growth form