Stem Respiration Of Rubber Trees And Influencing Factors

With the increase of the concentration of CO2, the threat that the climate brings is more and more obvious, which will ultimately threat human being’s survival. The change of the atmospheric CO2concentration depends on the fluctuation of exchange between the libraries that each carbon participates in the carbon cycle. There is about40%carbon stored in the forest in the global land ecological system. Tree trunk is the largest biomass storage and the long and huge carbon library. Trees metabolic breath can release the CO2, consuming more than50%of their photosynthetic carbon fixed. Rubber forest is widely distributed in tropical regions, especially in Hainan, Yunnan and Guangdong province and is one of the most important vegetations. Understanding the inside and outside factors that influence the rubber tree trunks breathing and the carbon change in ecological system to trunk breathing are the necessary steps to build and calibrate the ecological system carbon cycle model of Rubber forest. Meanwhile, they also may provide the scientific basis to reveal the effect brought by Rubber forest ecological system on slowing down the atmospheric CO2concentration changes.This study uses Li-6400portable breathing apparatus to test rubber respiratory rate of Rubber trunk at the rubber plantations of tropical Chinese academy of agricultural sciences in Dan Zhou city Hainan province. In this study, the author adopts multiple comparison and linear regression method to explore breathing characteristics and differences between different strains of rubber and the same trunk with different sizes, the trunk breathing of different height and direction, the daily change and the dynamic principle of seasonal change and the factors that influence the breathing of the rubber trunks. The main findings of the study are as follows:(1) The experiment excludes the effect brought by temperature and trunk size. The findings are that there exists difference on breathing among ReYan7-20-59, ReYan7-33-97and PR107; the respiratory rate of ReYan7-20-59is significantly higher than PR107, while there is no significant difference between ReYan7-33-97and the others.(2) By the comparison of breathing of different size of the same level trunk lines, trunk respiratory rate of40cm is greater than that of other six measured level trunk. If40cm trunk breathing is excluded, from the trunk size of50cm to100cm, the trunk respiratory rate increase with the increase of diameter circumference, at this time the tree trunk size shows a certain linear relationship with the respiratory. (3) There exists significant difference between the southern and northern sides of trunk breathing due to the seasonal changes and daily change. The respiratory rate of the southern side is greater than that of the northern side. However, there is no different of the same tree with different height.(4) Trunk breathing obviously shows consistent change with the seasonal trend, respiratory rate from the beginning of the measurement in April rises gradually, and in August it reaches the maximum peak. Then it begins to slow down and it is on the lowest level in January and then goes up. The respiratory rate value between day and night are obviously different, in the single-peak curve, and within the same treatment, the change trend of different direction and height is also consistent, mainly influenced by the temperature. The trunk respiratory rate varies with the temperature changes between night and day. The respiratory rate is higher in the growing season than that of non-growing season.(5) The influence of environmental factors on rubber tree trunks breathing. Temperature is one of the most important factors to influence trunk breathing. Trunk temperature and breathing are correlating, and with the rise of temperature, respiratory rate increases correspondingly; while trunk breathing and air humidity are negatively correlating. The air humidity of the bark surface increases, then the respiration rate of the stem decreases.(6) There is a significant difference of trunk respiratory rate between normal tree and trunk with dead bark. The respiratory rate of dead bark trunk is smaller than that of normal tree trunk.(7) The respiratory rate of the tapping surface is significantly higher than that of th e rubber tree with native skin.(8) Testing the trunk breathing before and after tapping rubber trees. Through the comparison, the study finds that the impact of the tapping stimuli is not big on the trunk breathing.