NPP changes of Larix chinensis estimated by tree-ring data and its response to climate change in the northern and southern slopes of Mt. Taibai, central China

Abstract:

Larix chinensis is mainly distributed in timberline of Mt. Taibai in the Qinling Mountains, a critical geographic demarcation for climate and vegetation distribution in China. Combined with biomass equations and the annual diameter at breast height calculated from tree-ring widths and investigation data of sampling plots, annual biomass and net primary productivity (NPP) of L. chinensis in northern and southern slopes were estimated. Correlation and response analyses were used to illustrate the relationship between the climate and NPP. The results show that from 1949 to 2014, the biomass of L. chinensis in the pure forests increases from 54.03 to 94.43 t/ha in the northern slope and 28.32 to 55.80 t/ha in the southern slope. The NPP of L. chinensis in northern and southern slopes has varied concordantly over the past 65 years, with an average value of 0.62 and 0.42 t/(ha·a) respectively. The difference in NPPs between the northern and southern slope is decreasing for the slight decrease trend of NPP in northern slope. Temperature plays an important role in the growth of L. chinensis. Low temperature before the growing seasons (from pervious November to April) and warm conditions in the growing seasons (mainly from June to July) can increase the growth of L. chinensis. However, the relationships between NPP and temperature are different in the northern and southern slope. The NPP in southern slope is more positively correlated with the temperature in the growing seasons and there is no significant correlation relationship between the NPP and the temperature in previous winter (from pervious November to January), while the NPP in northern slope is more negatively correlated with the temperature before the growing seasons. These results will provide useful information for the future research of forest carbon cycling.