Population dynamics of Betula ermanii in response to climate change at the Changbai Mountain treeline, China

To elucidate the mechanisms underlying the population dynamics of Betula ermanii in response to climate change over temporal and spatial dimensions, 310 quadrats were systematically sampled in 7 plots located in the upper treeline region on the north-facing slopes of Changbai Mountains. IKONOS images were used to identify the spatial distribution of Betula ermanii with the aid of a digital elevation model (DEM). Meteorological data were recorded in the field throughout the study area and collected from a nearby long-term weather station, to reconstruct the temperature and precipitation changes. We collected tree-ring samples from a total of 1197 Betula ermanii trees. The correlation coefficients between 14 eco-climate parameters (from 1953 to 2008) and the aggregated annual indices of population dynamics for each quadrat (totaling 310 quadrats) in the corresponding years were calculated via statistical analysis facilitated by GIS technology. The results show that the Betula ermanii population is more sensitive to changes in air temperature, than to change in precipitation. During the period when air temperatures increased at a slower pace, the Betula ermanii population steadily expanded via asexual reproduction and showed higher survival rate. During the period when air temperatures increased rapidly, the Betula ermanii population responded via rapid sexual reproduction and produced a large number of progeny.