Responses of shelterbelt stand transpiration to drought and groundwater variations in an arid inland river basin of Northwest China

Abstract

s u m m a r yPlant water use characteristics and transpiration responses under dry conditions are considered essential for effective and sustainable ecosystem management in arid areas. This study was conducted to evaluate the response of shelterbelt stand transpiration to precipitation, soil drought and groundwater variations in an oasis-desert ecotone in the middle of the Heihe River Basin, China. Sap flow was measured in eight Gansu Poplar trees (Populus Gansuensis) with different diameter at breast height over three consecutive growing seasons (2012)(2013)(2014). The groundwater evapotranspiration via plant use was estimated by the White method with diurnal water table fluctuations. The results showed that precipitation increased the stand transpiration but not statistically significant (paired t-test, p > 0.05). The recharge of soil water by irrigation caused stand transpiration acceleration significantly (t-test, p < 0.05). Stand transpiration and canopy conductance increased by 27% and 31%, respectively, when soil water conditions changed from dry to wet. Canopy conductance decreased logarithmically with vapor pressure deficit, while there was no apparent relationship between canopy conductance and solar radiation. The sensitivity of canopy conductance to vapor pressure deficit decreased under dry soil conditions. Groundwater evapotranspiration (0.6-7.1 mm day À1) was linearly correlated with stand transpiration (1.1-6.5 mm day À1 ) (R 2 = 0.71), and these two variables had similar variability. During the drought period, approximately 80% of total stand transpiration came from groundwater evapotranspiration. This study highlighted the critical role of irrigation and groundwater for shelterbelt, and might provide the basis for the development of water requirement schemes for shelterbelt growth in arid inland river basins.

Effects of terracing on soil water and canopy transpiration of Pinus tabulaeformis in the Loess Plateau of China

“…In time and space, soil moisture plays an important role in connecting environmental fluctuations and vegetation transpiration (Brito et al, 2015;Chen et al, 2014a). Similar to the conclusions drawn by Shen et al (2015), our results showed that canopy transpiration and canopy conductance of P. tabulaeformis were 6.9% and 3.9% higher at terrace site than that at slope site, respectively. Our results suggested that the impact of terracing on transpiration could be explained by the response of canopy transpiration to other environmental factors under different soil water conditions.…”

“…6) can be attributed to the influence of various environmental factors (Bosch et al, 2014;Brito et al, 2015;Chen et al, 2014c). Among these factors, VPD and solar radiation can trigger a timely response in transpiration, while the influence of soil water is reflected over a longer temporal scale (Chen et al, 2014a;Shen et al, 2015).…”

“…7). Studies have shown that the effectiveness of stomatal conductance induced by VPD fluctuation could result in the variation of transpiration rate (Addington et al, 2004;Igarashi et al, 2015), and a decline in canopy conductance with increasing VPD is an indicator of physiological restrictions to transpiration (Chang et al, 2014a;Shen et al, 2015). This occurred to avoid any highly negative values of leaf water potential and the subsequent xylem cavitation (Addington et al, 2004;Wang et al, 2014b).…”

Effects of terracing on soil water and canopy transpiration of Chinese pine plantation in the Loess Plateau, China

“…In time and space, soil moisture plays an 232 important role in connecting environmental fluctuations and vegetation transpiration (Brito et al, 233 2015;Chen et al, 2014a). Similar to the conclusions drawn by Shen et al (2015), our results 234…”

“…In addition to soil moisture, the low regression coefficient 214 can be attributed to the influence of various environmental factors (Bosch et al, 2014;Brito et al, 215 2015;Chen et al, 2014c). Among these factors, VPD and solar radiation can trigger a timely 216 response in transpiration, while the influence of soil water is reflected over a longer temporal 217 scale (Chen et al, 2014a;Shen et al, 2015). 218…”