Dynamic Of Biomass And Its Correlation With Water Factors In Regenerative Tropical Montane Rainforest Of Jianfengling,Hainan Island

The structure and function of ecosystems has changed with the intensification of climate change.Therefore,more and more attention has been paid to the response of terrestrial ecosystems to climate change.Tropical forests play a key role in the estimation of global C balance and C budget by being considered as one of the most important terrestrial ecosystem.Check data of long-term monitoring regenerative tropical montane rainforest plots(P8401?P8402?P8901)from 1984 to 2013 in Jianfengling,Hainan Island and generalized additive models(GAM)were utilized to simulate the long-term dynamic changing characteristics of biomass.By the long-term meteorological data of Tianchi meteorological station in Jianfengling,we analyzed the long-term dynamic changing characteristics of environment factor index including Maximum Climatological Water Deficit(MCWD)and different grade rainstorm events.Correlation between net changes of biomass and biomass mortality and extreme climate environment factor index in order to study the environment drive mechanism of carbon sequestration of regenerative tropical montane rainforest in Jianfengling.The results showed that:(1)According to check data of long-term monitoring plots,annual variance ratio of mean carbon density of tropical montane rainforest was 0.71 ± 0.22 Mg·C·hm-2·a-1 from 1984 to 2013 in Jianfengling which was tropical forest of high carbon sink rate.The increase of biomass density and decrease of net changes of biomass showed that carbon sequestration ability of regenerative tropical montane rainforest in Jianfengling weakened.This was mainly due to biomass mortality presented a significant(P<0.01)increasing tendency,increase of biomass mortality was associated with increase of stem number dying and losses per stem(P<0.05)significantly.Biomass recruitment,stem number of recruits had a significant increasing tendency and growth gains per stem had an increasing tendency,and they presented an obvious annual variation compared with biomass mortality.The number of living plants presented a decreasing tendency while the biomass of those showed a significant(P=0.0014)increasing tendency.(2)Time scales of a day,a period of ten days and a month were used to describe the dynamics changing characteristics of Maximum Climatological Water Deficit(MCWD)from 1980 to 2013 in Jianfengling.The results showed that MCWD value presented a decreasing tendency on a day scale while showed an increasing tendency on a period of ten days and a month scale.Researchs on the dynamics changing characteristics of annual rainstorm precipitation and days of different grade rainstorm events from 1980 to 2013 in Jianfengling.The results showed that annual rainstorm precipitation had a dynamic balance of 50 mm and 100 mm storm events.However,annual rainstorm days had a weakly increasing tendency on a 50 mm storm scale while appeared a decreasing tendency.(3)Drought was the major drive to lead that biomass of regenerative tropical montane rainforest in Jianfengling had a decreasing tendency.Correlation analysis showed MCWD value had a significant(P<0.01)negative correlation with net changes of biomass and a significant(P<0.01)positive correlation with biomass mortality.There appeared a critical threshold of rainstorm precipitation of different grade rainstorm events and correlation of net changes of biomass and biomass mortality.It showed that only value of rainstorm precipitation was higher than critical value could MCWD have a significant(P<0.01)negative correlation with net changes of biomass and a significant(P<0.01)positive correlation with biomass mortality.