Study On The Ecological Stoichiometry Of Tropical Rainforest In Xishuangbanna And Its Response To Gradient Effect

The impact of human activity on the global forest system is increasing,the most typical of which is the gradual decline of tropical rainforests.Include the tropical rainforest in Xishuangbanna.In recent years,global warming and extreme climate events have accelerated the drying rate of region,changing the climate characteristics and gradient effect of terrestrial ecosystem.This paper takes China's largest rainforest ecosystem in Xishuangbanna as the research object.Through field observation and laboratory analysis,a new approach was utilized to research element ecological stoichiometry of carbon(C)nitrogen(N)and phosphorus(P)in the soil-leaf-litter system of soil-vegetation system in tropical rainforest,and study element the biological geochemistry circulation how to response to altitude gradient,moisture and heat conditions and the gradient of elemental cycle.To discussed the biogeochemical cycling characteristics of rainforest system and its regional response to global change.Faced the double pressure on climate change and human activities,how to evaluate the response to changes in the structure and function of rainforest ecosystem on the environment,and effectively protect rainforest provide the basic information.After thorough analysis and in-depth discussion,we give some main conclusions as followed:1)The contents of C,N,P,and C/N,C/P and N/P values of soil,leaf and litter in Xishuangbanna rainforest were 62 mg/g?2.41 mg/g?0.56 mg/g?53.02?321.85?11.47;396.21 mg/g?24.22 mg/g?1.81 mg/g?19.92?577.09?29.98;362.61 mg/g?13.79 mg/g?1.49 mg/g?33.69?662.78?21.71,respectively.For the soil,in addition to STP,there are different degrees of variability in dry and wet season,different sample plots and rainforest types.Leaf TC by three influence factors,and the changes of TN and TP is more complex.Except for C/N of litter in dry season,other parameters of litter were significant differences in forest sample plots(p < 0.05;p <0.001),while the variability in rainy season and the rainforest types is more complex.Moreover,N/P indicates that the Xishuangbanna rainforest is restricted by P,especially montane rain forest is more serious.2)The correlation analysis of ecosystem stoichiometry of soil-plant system shows that there are obvious gradient of element cycle and coupling relationships between C,N,P and its stoichiometric of soil-leaf-litter system,and this coupling relationship is affected by dry and wet season and rainforest type,and has a duality in spatial characteristics complex coupling correlation.Such as rainy season SOC directly affect STN,C/N and leaf TP and C/P levels,and the lower level of STP may be due to the higher utilization of leaf TC,TN,TP,C/N.With the significant correlation between leaf TC and leaf TN,litter TC,TN,and between leaf TN and litter TC showed that the change of any element of C,N and P in soil-leaf-litter system could change the whole the elemental biogeochemical cycle equilibrium.3)Affected by elevation and hydrothermal gradient,the SOC was significantly affected by altitude(p < 0.01),while STN with elevation was a single peak change pattern,which was affected by the rainforest type and the dry and wet seasons.And the relationship between altitude and STP,C/P,C/N and N/P was not significant in the rainforest type and dry and wet seasons(p > 0.05),which illustrates that the utilization levels of N and P in leaves of two rain forest types are less affected by altitude gradients as affected by dry and wet seasons.The results showed that altitudinal gradient,leaf for the utilization level of C and N and the assimilation ability of plant N for C were different in the two types of rainforest.The response of forest litter to the elevation gradient was significantly affected by forest type,climatic conditions and seasonal alternation.4)If the N rainforest settlement ratio increases,due to the enhancement of carbon sequestration capacity of plant leaves,and improve the utilization efficiency of P,and the soil plant system elements coupling relationship and the limit indication function of ecological stoichiometry,it will accelerate the circulation rate of phosphorus of rainforest system,long-term succession,will make the P elements of more lack of rainforest,and then destroy the balance of forest ecosystem,threaten some species survival,especially season rainforest.However,there are many factors affecting the change of carbon in the soil-vegetation system of tropical rain forest so that incapable exact evaluate soil carbon.