Time lag of stem water deficit in response to vapor pressure deficit of Castanopsis hystrix
[Objective]Tree water deficit-induced stem shrinkage(TWD)is an indicator for tree water status.By studying the variation characteristics of TWD and its relationship with VPD,and revealing the response characteristics of radial change to environmental water stress,the scientific basis and data support for reasonable guidance of Castanopsis hystrix plantation management was provided.[Method]Dendrometer was used to continuously record the radial growth change process of C.hystrix,and the environmental factors were measured simultaneously.The main goal of this study was to analyze the response characteristics of TWD to VPD.[Result]The TWD fluctuation trend of different differentiation classes was similar,and TWD varied with VPD,but not synchronously.On the hourly scale,TWD and VPD were significantly positively correlated(r=0.488,r=0.489,r=0.512,P＜0.01),and TWD and VPD were also significantly positively correlated after the water loss period and water recover period were divided.The correlation of water loss period was enhanced(r=0.623,r=0.667,r=0.593,P＜0.01).On the daily scale,no matter whether water loss period and water recovery period were divided,the two were significantly positively correlated,but the correlation was weakened.The results of comparison of pearson's correlation coefficients between TWD and VPD under the condition of considering the time delay effect within 1-day showed that TWD and VPD were significantly positively correlated(P＜0.01)regardless of differentiation classes.After dividing the water loss period and the water recovery period,the correlation of the water loss period was stronger than that of the water recovery period.When the water loss period and the water recovery period were not divided,the variation of TWD lagged behind that of VPD to a certain extent,by about 3 h.After the water loss period and the water recovery period were divided,the time lag of TWD to VPD in the water loss period was shortened,and time lag of TWD to VPD in the water recovery period was lengthened.The time lag of dominant,intermediate,and suppressed trees during water recovery period was 3 h,4 h and 5 h,respectively,longer than that during the water loss period.Under VPD large fluctuation condition(VPDL),with repeatedly rising and falling of VPD,TWD appeared as water loss and recovery alternately.Under VPD small fluctuation condition(VPDs),TWD changed slowly.The time lag of TWD to VPD was existed under both conditions.The correlation between TWD and VPD under VPDL was stronger(r=0.550,r=0.553,r=0.584,P＜0.01)than that under VPDs(r=0.256,r=0.260,r=0.281,P＜0.01),regardless of differentiation classes.Under VPDL,after considering the time lag,the correlation between TWD and VPD of different differentiation classes was enhanced regardless of whether the water loss period and the water recovery period were divided.Under VPDs,the correlation of water recovery period was lower than that when the time lag effect was ignored.[Conclusion]TWD has a time-lag effect in response to VPD.TWD has different response characteristics to VPD in the water loss period and water recovery period,and these relationships have differences among different tree differentiation classes.The division of water loss period and water recovery period is helpful to study the correlation between TWD and VPD.
万方数据
维普
