The effect of climate on the net primary productivity (NPP) of Pinus koraiensis in the Changbai Mountains over the past 50 years

This study investigated the relationship between climate and Pinus koraiensis net primary productivity (NPP) (estimated using tree-ring widths) and the effect of climate on NPP in the Changbai Mountains. Three typical areas of Pinus koraiensis and a broad-leaved mixed forest were investigated and sampled. NPP was estimated using biomass equations and the annual diameter at breast height, calculated from tree-ring widths. A stepwise regression was used for the quantitative analysis of the response of NPP to climate variation, whereas correlation and response analyses were used to illustrate the relationship between the climatic variables and NPP. The results showed that between 1960 and 2012, the biomass of sampled Pinus koraiensis in the Changbai Mountains almost doubled, from 107.70 to 205.29 t ha(-1). The NPP of Pinus koraiensis varied steadily within a confined range over the past 52 years, with an average of 1.88 t ha(-1) year(-1). In this study, it was deduced that NPP was simultaneously affected by temperature and precipitation. The minimum temperature in April and the precipitation in June and July, which most affected the changes in NPP, could explain 28.4 % of the NPP variance. The extreme values of these principal climatic controls corresponded well with extreme NPP values. However, an increase in NPP caused by recent warming prior to the growing season might have been offset by a decrease in summer precipitation. Furthermore, the effect of temperature change on NPP was complex. An increase in monthly low temperatures induced by warming acted to increase NPP, while the monthly high temperatures during the growing season had a negative impact on NPP for the drought.