干旱对西双版纳望天树液流密度的影响OA

To reveal the dynamic patterns of sap flow density and its response relationships with environmental factors in Para-shorea chinensis under drought conditions,we took P.chinensis in Xishuangbanna as research material and conducted ana-lyses on the effects of drought on sap flow density based on auxiliary observation plots in the artificial tropical rainforest of Xishuangbanna Tropical Botanical Garden,Chinese Academy of Sciences.The results showed that:(1)The seasonal dy-namics of sap flow density of P.chinensis were characterized by high values in the rainy and fog-cool seasons and low val-ues in the hot-dry season.However,its fluctuations intensified markedly in 2020,which was identified as a year with per-sistent drought throughout the year according to the Palmer drought severity index(PDSI).(2)Regression analysis indi-cated that the sap flow density of P.chinensis in normal years was primarily regulated by different environmental factors in each season(P<0.05):photosynthetically active radiation(R2≥69%)in the fog-cool season,relative humidity(R2≥38%)in the hot-dry season,and vapor pressure deficit(R2≥13%)in the rainy season.The persistent drought in 2020 weakened the regulatory effects of photosynthetically active radiation(R2=22%),vapor pressure deficit(R2=28%)and relative humidity(R2=33%)on sap flow density during the hot-dry season.(3)Under drought stress in 2020,the sensi-tivity(absolute slope values)of sap flow density to relative humidity and vapor pressure deficit decreased significantly,with values of 0.81±0.17 and 0.24±0.09,equivalent to only 52%and 55%of the values in 2021,and 47%and 36%of those in 2022,respectively.Meanwhile,the optimal relative humidity threshold for sap flow density declined significantly from 63%-65%in non-drought years to approximately 40%in the drought year,whereas the optimal vapor pressure deficit threshold increased significantly from 0.52-0.64 kPa to around 1.04 kPa(P<0.05).