Transpiration And Water Consumption In A Grapevine Canopy In An Arid Oasis Ecosystem

Plant transpiration(Ec) is a subject of increasing research interest, especially in regions where transpiration is a fundamental datum in understanding the ecophysiology of plants. Thus, accurate measurement of Ec are essential for many applications in arid region of northwest China, such as irrigation scheduling, yield forecasts and ecological conservation.Based on measurements of sap flow, meteorological and biological factors in an oasis vineyard in Northwest China in two years, this study measured sap flow of single tree and analyzed water consumption of grapevines. Values of Ec was estimated by multiplying the average sap flow per leaf area unit by the leaf area index, and then canopy conductance(gc) was calculated and the relationships between gc and meteorological variables were examined and modeled. This study also measured evapotranspiration of grapevine by using eddy covariance technique(ETec), and compared it with Ec upscaled by sap flow data. The results showed that,(1) sap flow velocity varied in different weather conditions and different months, and the water consumptions of grapevines increased exponentially with the increase of its diameter at breast height.(2) Relationships between gc and meteorological variables exhibited hysteresis loops, and the responses of gc to meteorological variables and its controlling factors were significantly different during different daytime periods. Hysteresis loops were also observed and exhibited a significant seasonal variation at different stages of the vine growth and development. The multistage models used in this study were reasonably precise and reliable to simulate variations in gc.(3) The comprehensive usage the sap flow method and eddy covariance technique can help us to efficiently identify the characteristics evapotranspiration and its different components. The ratio of daily Ec to daily ETec was about 85.8 %, evapotranspiration of grapevines was dominated by canopy transpiration in the full canopy periods.This study comprehensively clarified the variation patterns of Ec, ETec and gc of a grapevine canopy, and the results will be beneficial to improve our understanding of the feed backs between the planted land surface and the atmosphere in an oasis ecosystem, and provide fundamental basis for water availability, distribution and management in arid region of northwest China.