Study On Dynamic Change And Influencing Factors Of Carbon Water Flux And Water Use Efficiency Over A Poplar Plantation In Lake Hongze Basin

It is of great significance to study carbon water exchange and water use efficiency in forest ecosystem to analyze the carbon water cycle and carbon sequestration capacity of forest ecosystem,and there are few researches on carbon water flux and ecosystem water use efficiency in Hongze Lake basin at present.In this study,the carbon and water exchange between the forest ecosystem and the atmosphere was measured and analyzed by using eddy covariance technique in the poplar plantation ecosystem of Hongze Lake basin,which is located in the north subtropical and warm temperate regions of China.Dynamic variation characteristics of carbon and water flux and ecosystem water use efficiency and their responses to external meteorological environmental factors.Analysis of carbon water flux and water use efficiency in ecosystem scale by selecting flux observation data from May 2017 to December 2018 in Hongze Lake basin.The dynamic characteristics of carbon and water flux in plantation ecosystem and its relationship with meteorological environmental factors provide the necessary basic data for assessing carbon sequestration capacity and water use efficiency of poplar plantation.It reveals the carbon cycle of forest ecosystem and its response to environmental factors,and provides scientific basis for enhancing carbon sequestration capacity of forest ecosystem.The main conclusions obtained are as follows:There were significant seasonal and diurnal variations in carbon fluxes of poplar plantation ecosystem in Hongze Lake basin.NEE was carbon sink during day and carbon source at night.The diurnal variation of carbon flux of poplar plantation in Hongze Lake basin was"U"curve in both growing and non-growing seasons.Carbon uptake in the growing season was significantly higher than that in the non-growing season.The annual flux of-594.4 g C·m^-2·yr^-1.There was a significant correlation between NEE and environmental factors PAR?VPD?Ta?RH and Ts.The GEP?ER and LE fluxes in the ecosystem had significant seasonal variations,which were higher in the growing season and smaller in the non-growing season than in the non-growing season.The annual accumulative values of GEP in the ecosystem are 1231 g C·m^-2·yr^-1,and the total respiratory ER of ecosystem was 636.6 g C·m^-2·yr^-1.There was obvious seasonal dynamic change of ET of poplar plantation ecosystem in Hongze Lake basin,and ET was significantly positively correlated with PAR and Ta during the growing season during the growing season.WUE_E of poplar plantation ecosystem in Hongze Lake baisn had no obvious seasonal change.However,the diurnal variation trend of WUE_E in different seasons is significant in growing season and non-growing season as well as in different seasons.The variation of WUE_E in different seasons was:spring>winter>autumn>summer.The annual average value of WUE_E for the whole year of 2018 is 2.2g C·kg^-1H₂O.There was a significant negative correlation between environmental factor VPD and WUE,and a significant positive correlation between Ta and WUE_E.The seasonal and diurnal variation trend of the methane flux in the poplar plantation ecosystem in Hongze Lake basin was relatively gentle.The methane was weak in the whole year,and the growth season is a weak methane sink,and the non-growing season was a very weak source of methane.There was a weak positive correlation between CH₄ and SWC in the growing season,a weaker negative correlation with Ts in the non-growing season,and no correlation with Ta during the growth season and the non-growing season.The poplar plantation ecosystem in Hongze Lake basin has high carbon sequestration ability,and the carbon water flux and water use efficiency of ecosystem are significantly influenced by environmental factors,which provides reference for improving the carbon sequestration ability of poplar plantation.