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| 1 | Actual evapotranspiration of subalpine meadows in the Qilian Mountains, Northwest China显示文摘As a main component in water balance,evapotranspiration(ET)is of great importance for water saving,especially in arid and semi-arid areas.In this study,the FAO(Food and Agriculture Organization)Penman-Monteith model was used to estimate the magnitude and temporal dynamics of reference evapotranspiration(ET0)in 2014 in subalpine meadows of the Qilian Mountains,Northwest China.Meanwhile,actual ET(ETc)was also investigated by the eddy covariance(EC)system.Results indicated that ETc estimated by the EC System was 583 mm,lower than ET0(923 mm)estimated by the FAO Penman-Monteith model in 2014.Moreover,ET0 began to increase in March and reached the peak value in August and then declined in September,however,ETc began to increase from April and reached the peak value in July,and then declined in August.Total ETc and ET0 values during the growing season(from May to September)were 441 and 666 mm,respectively,which accounted for 75.73%of annual cumulative ETc and 72.34%of annual cumulative ET0,respectively.A crop coefficient(kc)was also estimated for calculating the ETc,and average value of kc during the growing season was 0.81(ranging from 0.45 to 1.16).Air temperature(Ta),wind speed(u),net radiation(Rn)and soil temperature(Ts)at the depth of 5 cm and aboveground biomass were critical factors for affecting kc,furthermore,a daily empirical kc equation including these main driving factors was developed.Our result demonstrated that the ETc value estimated by the data of kc and ET0 was validated and consistent with the growing season data in 2015 and 2016. | GAO Yunfei ZHAO Chuanyan Muhammad W ASHIQ WANG Qingtao RONG Zhanlei LIU Junjie MAO Yahua GUO Zhaoxia WANG Wenbin | 2019 | Journal of Arid Land2019，11，3： | 8 |
| 2 | Leaf gas exchange and photosynthesis curves of Elymus nutans and Potentilla anserina under fencing and grazing conditions in the Qilian Mountains, Northwest China显示文摘Potentilla anserina L.and Elymus nutans Griseb.are dominant species in the subalpine meadows of China.Grazing is one of the most important factors that influence community structure and productivity of subalpine meadows.Understanding how grazing changes photosynthetic capability is essential for preservation and restoration of grasslands.However,information about the effects of grazing on photosynthetic capability remains inadequate.Experiments were conducted in fencing and grazing areas in the Qilian Mountains,Northwest China.The leaf gas exchange and photosynthetic curves of P.anserina and E.nutans were measured at different growth stages.Results showed that grazing decreased the values of leaf gas exchange parameters,such as net photosynthetic rate,stomatal conductance,transpiration rate,and intercellular CO2 concentration of P.anserina and E.nutans.In addition,grazing decreased the values of net photosynthetic rate-photosynthetically active radiation(PN-PAR)curve parameters,such as light-saturated net photosynthetic rate,apparent quantum efficiency,light compensation point,light saturation point,and dark respiration rate.Our results demonstrated that grazing was the primary limiting factor for photosynthesis of dominant grassland species in the study area. | LIU Junjie WANG Xiaoping GAO Yunfei RONG Zhanlei ZHANG Guangde WANG Wenbin GE Lijuan MAO Yahua GUO Zhaoxia ZHAO Chuanyan | 2019 | Journal of Arid Land2019，11，3： | 3 |
| 3 | Modified non-rectangular hyperbola equation with plant height for photosynthetic light-response curves of Potentilla anserina and Elymus nutans at various growth phases in the Heihe River Basin, Northwest China显示文摘The non-rectangular hyperbola(NRH)equation is the most popular method that plots the photosynthetic light-response(PLR)curve and helps to identify plant photosynthetic capability.However,the PLR curve can't be plotted well by the NRH equation at different plant growth phases due to the variations of plant development.Recently,plant physiological parameters have been considered into the NRH equation to establish the modified NRH equation,but plant height(H),an important parameter in plant growth phases,is not taken into account.In this study,H was incorporated into the NRH equation to establish the modified NRH equation,which could be used to estimate photosynthetic capability of herbage at different growth phases.To explore photosynthetic capability of herbage,we selected the dominant herbage species Potentilla anserina L.and Elymus nutans Griseb.in the Heihe River Basin,Northwest China as the research materials.Totally,twenty-four PLR curves and H at different growth phases were measured during the growing season in 2016.Results showed that the maximum net photosynthetic rate and the initial slope of PLR curve linearly increased with H.The modified NRH equation,which is established by introducing H and an H-based adjustment factor into the NRH equation,described better the PLR curves of P.anserina and E.nutans than the original ones.The results may provide an effective method to estimate the net primary productivity of grasslands in the study area. | LIU Junjie WANG Xiaoping RONG Zhanlei GAO Yunfei ZHANG Guangde WANGWenbin GE Lijuan MAO Yahua GUO Zhaoxia WANG Qingtao ZHAO Chuanyan | 2019 | Journal of Arid Land2019，11，5： | 1 |
| 4 | Spatiotemporal patterns of precipitation based on the Bayesian maximum entropy method in a typical catchment of the Heihe River watershed,northwest China显示文摘Precipitation patterns are vital to water resource management and hydrological research,especially in the upper reaches of inland rivers in arid and semiarid areas.However,estimating spatiotemporal precipitation patterns at a basin scale is challenging due to limited observations.In this study,spatiotemporal patterns of precipitation amount,frequency,duration,and intensity at different time scales from 2014 to 2019 are estimated using the Bayesian maximum entropy method in the Tianlaochi catchment of the Heihe River watershed,northwest China.The study's results show that the annual average precipitation amount was 535.9 mm from 2014 to 2019,with precipitation amount between May and September accounting for 85.9%of the annual precipitation amount.For daily precipitation,the average frequency rate of light precipitation is highest at 59.55%,however,the average contribution rate of moderate precipitation is highest at 50.33%.The spatial distribution of precipitation is characterized by high-value areas concentrated in the central valley and low-value areas located at the catchment's outlet.The most important driving factors of precipitation patterns are elevation,relative humidity,and wind direction.These outcomes can be used to establish accurate hydrological models in the catchment and provide support for water resource management in the Heihe River watershed. | Hong Wang Chuanyan Zhao Fei Zang Zhanlei Rong Yapeng Chang Youyan Liu | 2022 | International Journal of Digital Earth2022，15，1： | 0 |
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