Influence of forest age, tree size, and climate factors on biomass and carbon storage allocation in Chinese fir forests

Abstract

Biomass and carbon allocation among plant organs are influenced by the individual tree's development and climate conditions. Chinese fir forests play an important role in the carbon cycle and climate change mitigation in China. Understanding how forest age, tree size, and climate factors affect biomass and carbon allocation in Chinese fir forests is crucial to fully utilize the carbon sequestration potential. We analyzed the response of Chinese fir biomass allocation fractions (BAFs) and carbon stock allocation fractions (CAFs) to forest age, tree size, and climate factors, utilizing field survey data on biomass of 93 trees in Fujian, Sichuan, Guangxi, and Jiangxi provinces and carbon storage of 40 trees in Fujian, Sichuan, and Guangxi provinces in China. Our results showed that BAFs depend on individual development. In young and middle-aged forests, BAFs were unaffected by diameter at breast height (DBH), whereas branch and root biomass fractions displayed a significant positive correlation with DBH, and stem biomass fraction displayed a negative correlation with DBH in mature forests. Carbon concentration exhibited substantial variation among distinct components and regions. Overall, the carbon concentration of each organ ranked as Guangxi > Sichuan > Fujian. BAFs of dominant trees are almost independent of climatic factors, while suppressed trees will alter their strategies for biomass allocation in response to climate change. Stem biomass fraction exhibited a significant positive correlation with maximum growing season temperature, mean summer temperature, and maximum summer temperature, whereas leaf biomass fraction showed the opposite trend. Under future climate warming, Chinese fir will allocate more biomass to the stem, at the expense of leaf biomass. These findings support the idea that biomass allocation patterns serve as adaptive patterns to address fluctuations in internal and external conditions. The interaction between climate factors and tree size shows promise for predicting trends in forest biomass and carbon accumulation in the context of future climate change.