基于通量观测的攀西烟区烟田水分利用效率特征研究

Dynamic characteristics of water use efficiency in Panxi tobacco planting area based on flux observation data

为揭示烟田生态系统水、碳通量和水分利用效率(WUE)的变化特征。基于2015—2016年攀西烟区涡度相关通量观测数据,分析烟田生态系统水、碳通量和WUE的时间动态特征,阐释烟田生态因子对水、碳通量和WUE的影响规律。结果表明:烟田WUE的日变化为日出后迅速升高,8:00~9:00达到最大值后逐渐降低,到14:00左右趋于稳定,傍晚前又有小幅度的增加;烟田WUE的季节变化呈"双峰"趋势,旺长期和成熟采收期前期较高,伸根期最低。烟田WUE与气温、净辐射均呈二次曲线关系,而与饱和水汽压差(VPD)呈负指数关系。气温、VPD和净辐射控制WUE变化的时间节点不同,其中VPD对WUE限制节点出现的时间较早,而气温、净辐射相对较晚,这主要与总初级生产力(GPP)和蒸散量(ET)对气温、VPD和净辐射变化的敏感度差异有关。根据不同生育期WUE变化规律的研究结果,降低土壤无效蒸发,增强叶片光合能力,是提高烟田生态系统水资源利用水平的关键途径。

Dynamics of water-carbon flux and WUE of tobacco field and effect of biological factors were investigated based on flux observation data from Panxi tobacco planting area in 2015-2016. Results showed that tobacco field WUE showed obvious diurnal and seasonal variations derived from dynamics of water-carbon flux. In daytime, WUE increased rapidly to maximum at 8：00-9：00, then decreased to minimum before evening. For the seasonal variation, the highest WUE was found in the stage of long term and mature harvest period. Statistical analysis indicated that there were quadratic relationships between WUE and air temperature as well as between WUE and net radiation, but there was an exponential decline relationship between WUE and vapor pressure deficit （VPD）. The driving effects of air temperature, VPD and net radiation on the increase of WUE showed temporal differences. During growing period, VPD was the main driving factor on increasing WUE at the beginning, followed by air temperature and net radiation. The temporal differences were mainly related to different sensitivity of gross primary production （GPP） and evapotranspiration （ET） to air temperature, VPD and net radiation. Therefore, to identify characteristics of WUE and its driving factors may significantly improve water resources management in tobacco fields of the study area.