ObjectiveCarbon content is one of the key factors when estimating carbon storage. Accurate measurement of carbon content and finding its influencing factors can improve the accuracy of the prediction of carbon storage.
MethodTree cores collected in the plots of mature forests in the broardleaved Korean pine forest of Jiaohe, northeastern China were taken as samples in this study. Carbon content of frozen, oven-dried and natural air drying samples of Pinus koraiensis from 1987 to 2016 were attained in order to qualify the volatile carbon content and to compare the characteristics of the interannual variation of the carbon content attained by different drying methods. In this passage, volatile carbon content was qualified with frozen and oven-dried carbon content considering the relative stability of them. The relationship between volatile carbon content and three climate factors as well as size class and annual growth was developed.
Result(1) The results showed that significant difference among carbon content of different drying methods was only found in trees of large diameter class.(2)The fluctuation characteristics of volatile carbon contribution differed in small and large class and the interannual variations were more remarkable in small class. The volatile carbon contribution reached 24.46% in small class and 9.72% in large class. Also, the volatile carbon contribution in large class lagged behind that of small class. (3)The volatile carbon contribution was mainly limited by the temperature in winter. In small class, the volatile carbon contribution showed negative response to temperature in December of that very year, while in large class, it responsed negatively to the temperature in last December. (4)The precipitation of this January had positive influence in volatile carbon contribution of large class and the volatile carbon contribution of small class showed positive response to PDSI of this June, which inspired us that the effect of volatile carbon may be related to trees' dormancy or other defensive mechanisms.
ConclusionTherefore, it is necessary to take volatile carbon content into account while estimating the forest carbon storage without ignoring the influence of size class. It is also necessary to make a deep analysis of the influencing factors of volatile carbon contribution.