The Response Of Treeline Dynamics To Climate Change On North Slope Of Changbai Mountains

The significant climate warming has received high attention with increasingly serious global environmental problem. Many researchers are interested in response modes and coping strategies of ecosystem to climate change. Alpine treeline is regarded as highly sensitive and potential indicator of climate change. Therefore, Alpine treeline has become one of the hotspots in global climate change research. Changbai Mountains lies in the eastern region of Northeast China with the well-known montains in Northeast Asia. Alpine treeline of north-facing slopes of Changbai Mountains provides an excellent opportunity to explore its characteristics associated with climate change. This paper aimed to understand the relationship between climate change and treeline dynamics, treeline as study area. The relationship was a breakthrough point to reveal how expanse strategies of ecosystem to climate change.We sampled 7 typical plots located in the treeline on the north-facing slopes of Changbai Mountains as study area using some mathematical statistics methods associated with GIS and tree-ring technologies, based on remotely sensed information, digital elevation model (DEM), measured meteorological records, tree-ring analysis and field investigations. Specific objectives of this study are to 1) to examine climate change characteristics in the treeline at 56(1953-2008)and 149 years (1860-2008);2) analyze the relationship between Betula ermanii population dynamics and climate change;3) discover the response modes of treeline dynamics to climate change at community and landscape scale;and 4) understand the influence degrees of some factors related to topography and soil on the treeline change.The results of temperature change showed that there were three megathermal periods for 56 years and an obviously increasing trend since the late 1980s at Changbai Mountains treeline. Air temperature had wavelike rise for 149 years with cold and warm period’s alternation. Sustained time was gradually short in cold period and long in warm period. The warm periods overlap, rising amplitude and fluctuation range of air temperature would lead to hazard increase of ecosystem in Northeast China.population expansion of Betula ermanii was obvious as air temperature increasing. The tree height growth for Betula ermanii is divided into adaptive phase, low stress phase and high stress phase according to its size class from small to big at closed treeline. The tree height growth was the well-ordered at high temperature period. However, it was restricted at low temperature period. Different propagation forms and the annual stem recruitment of Betula ermanii population responded significantly to the fluctuation of air temperature increase. The population continued to vary its physiological traits for the population expansion and the domain enlargement. Under global warming background, the population expansion and the domain enlargement of Betula ermanii led to treeline shift. Statistics analyses and GIS technology were completed on the relationship betweenBetula ermanii population dynamics and climate change over temporal and spatial dimensions. The result of showed that Betula ermanii population responded significantly to climate change (high correlation coefficients). It was more sensitive to the change of air temperature than that of precipitation (correlation coefficients and including frequencies of air temperature> precipitation). Increases in air temperature led the population to expand differently along altitude from low to high. The results of statistics analyses showed that population expansion of Betula ermanii drove the shifts of shrub and grass belonged to forest community. Treeline shift was tree change. In addition, forest community invaded tundra community too. Therefore, The ecological niche of tundra community was excluded by forest community. Moreover, the change difference among different compositions of tundra was very obvious. The difference was very obvious during replacement process of varied plants due to the distinction of competitive and status in community.Based on 4 years’images (1989, 2000, 2005 and 2009) at treeline on North Slope of Changbai Mountains. Dynamics response pattern of treeline landscape to climate change was investigated using 22 landscape indices. The results showed that change complexity of patch area got bigber and the change pattern of patch shape area was easy at first and then became complex. Landscape pattern grudually became simple with wavy feature. The treeline landscape dynamics was in accordence with the wavy increase air tempreture. As air temperature quicly increased, landscape pattern and patch shape became complex. When air temperature steadily increased, patch shape became regular and landscape pattern was gradually simple. Air temperature increase made treeline landscape continue to ajust its feature in order to complete treeline shift.The interaction of two treeline shifts determined by warmth index (WI) and humid index (HI) respectively was not significant (p>0.05). In addition, there was negative correlation between two treelines change (r=-0.11<0). Therefore, Two treelines were unable to reach their potential height. The slope of Betula ermanii treeline was estimated as from 1975 to 2231m. The fluctuation process was simple in lower treeline. However, the complex fluctuation process in upper treeline indicated that fluctuation of treeline shift increased due to large stress. The results of correlation analysis and stepwise regression showed that different responses of population dynamics to climate change caused by different temperature on three slopes (southeast slopes, northeast slopes and east slopes). The differences of climate change led to different expansion of Betula Ermanii population on different positions. Soil factor had a certain restrictive function to population dynamics of Betula ermanii. However, it did not play a crucial role in treeline shifts. The population tended to continuously adjust its life forms to adapt air temperature change in order to overcome soil restrictions.