Effects Of Soil Warming And Isolating Rainfall On Osmotic Regulation And Stem Xylem Function Of Cunninghamia Lanceolata

A completely randomized trial was designed at the Forest Ecosystem and GlobalChange Research Observatory in Sanming,Fujian province to study the response of?Cunninghamia lanceolata?to climate warming and precipitation reduction..Four treatments were set up,the control group?CK?:no warming or isolation precipitation;isolated precipitation group?P?:no warming,isolation of 50%precipitation;warming group?W?:warming 5?,no isolation of precipitation;Warming and Isolation Precipitation?WP?:Increasing temperature by 5?and isolating 50%of precipitation..The temperature increase and precipitation isolation treatment time are 3 to 4 years,and the leaves and branches of the sample tree are collected to determine the metabolism of the leaves and the xylem embolism.The results show:1.There was no significant difference in the measured Dawn water potential between the leaves?Significance level 0.05?.;The soluble sugar content of Chinese fir leaves showed significant difference between treatments?Significance level 0.05?;There was no significant difference in the starch content of Chinese fir leaves?Significance level0.05?;the non-structural carbohydrate treatment group of Chinese fir leaves was significantly higher than the control group,The order of the soluble sugar/starch ratio of leaves was:warming,isolated precipitation group?WP?>warming group?W?>control group?CK?>isolated precipitation group?P?,ratio and non-structural carbohydrate NSC content showed extremely significant?Significance level 0.01?positive correlation;There was no significant difference in the content of C and N in the leaves of Chinese fir;the content of the isotope?¹³C control?CK?in the leaves of Chinese fir was-29.76‰,and the treatment did not have a significant effect on the isotope?¹³C.There was a significant correlation between the isotope?¹⁵N and the treatment of Chinese fir leaves?Significance level 0.05?,and the sampling time changed the isotopic?¹⁵N content significantly.The drought effect caused by warming is higher than that of isolated rainfall.The drought condition increases the soluble sugar content of the metabolically active organ of the leaf,and the leaf increases the soluble sugar content to meet the physiological metabolic demand under drought conditions.The starch content of the leaves gradually decreased with the temperature during the season alternation,and the starch content increased.It can be seen that in the case of drought conditions?warming and isolated precipitation?,the leaves tend to produce more non-structural carbohydrates to cope with the drought.The ratio of soluble sugar to starch in Chinese fir leaves also showed obvious regularity.Under the conditions of temperature increase and rainfall isolation,the leaves had higher soluble sugar/starch ratio,and the soluble sugar/starch ratio and leaf NSC content were Significant correlation.The C and N stoichiometry of the leaves are relatively fixed in the content of the leaves,and the ratio is relatively stable.The difference between the temperature increase and the isolated rainfall performance in the C and N stoichiometry of the leaves is very small.It can also be seen that as the season gradually turns to autumn,the isotope?¹⁵N of the leaves is also gradually negative?decreased?,indicating that the degree of?¹⁵N enrichment is reduced;At the same time,under the temperature increase and isolation rainfall,the isotope?15N content is significantly positive?increased?,which means that the enrichment of the isotope?15N is significantly increased under drought conditions,and the enrichment effect brought by the warming is significantly higher than the isolation rainfall.2.The measured water-conducting rate of the xylem of the Chinese fir was significantly positively correlated with the diameter of the branches?Significance level0.01?,but the treatment did not have a significant effect on the water conductivity of the xylem of the Chinese fir;The natural embolization rate of Chinese fir was 11.51%.There was no significant difference in the natural embolization rate of each treatment.The natural embolization rate was not affected by drought stress.The P₅₀0 of the fir reflecting the vulcanity of the xylem was-2.53 MPa,and the other treatments were-1.73 MPa?P?,-1.72 MPa?W?,and-1.65 MPa?WP?.