Variation of vegetation index in response to climate change on the eastern slope of Changbai Mountain, Northeast China

Abstract

Changbai Mountain is located in the heartland of the temperate coniferous and broadleaved mixed forest, which is sensitive to climate change. Studying how the tree-ring width of Larix olgensis and forest NDVI in the Changbai Mountain are related to climatic factors could lead to better understanding of the responses of the terrestrial ecosystem in the background of global climate warming. In this work, the tree-ring width index of L. olgensis in the eastern slope of Changbai Mountain, UMD GIMMS NDVI from 1982 to 2006, and the weather data of Tianchi were selected to analyze the relationships between the tree-ring width and NDVI and climatic factors, and to find out the relationship between radial growth of L. olgensis and NDVI in the eastern slope of Changbai Mountain. The simulated regression equations of the tree-ring index of L. olgensis and climatic factors, of biomass increment and NDVI, were established by multiple regression analytical method. The results were as follows: 1. Since 1957, the temperature of the region studied was in a highly significant rising trend, with winter temperatures changing most remarkably; but precipitation was in a weak downward trend. 2. From 1982 to 2006, NDVI of annual average, summer, and growing season decreased slowly. 3. The analysis of chronology characteristics of L. olgensis in Changbai Mountain showed that growth of L. olgensis was sensitive to the climate, thus applicable for ring climate analysis. 4. NDVI was strongly related to monthly average temperature with a positive correlation, but was negatively related to monthly precipitation. 5. Radial growth of L. olgensis was more strongly influenced by climatic factors in the growing season of the current year than that of the previous year, with different period of significant correlation, and higher impact of precipitation than temperature. 6. The tree-ring width and biomass increment of L. olgensis were mainly negatively correlated with NDVI. NDVI in the growing season was poorly correlated to tree-ring chronology, but NDVI outside growing season was well correlated to the chronology. 7. The stand aboveground biomass was 240.72 t/hm2 per unit area now, and the stand biomass increment was about 2.91 t hm-2 a-1 in 2009, which means about 1.46 t carbon sequestration per hectare per year. It indicated that forest of old Larix olgensis in the region still had a strong capacity of carbon sequestration. In summary, ring width data of long time is not adequate to reflect the variation trend of NDVI in the Changbai Mountain. Further study on the regional NDVI redevelopment is needed.