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Response of Populus euphratica *** flow to environmental variables for a desert riparian forest in the Heihe River Basin,Northwest China

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Journal of Arid Land 2016年第4期8卷 591-603页

作者： LI Wei si jianhua YU Tengfei LI Xiaoyan College of Resources Science and Technology Beijing Normal University Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences State Key Laboratory of Earth Surface Processes and Resource Ecology Beijing Normal University

Being an important desert riparian forest in the lower reaches of the Heihe River Basin, Populus euphratica Oliv. forest functions as a natural barrier in maintaining and preserving the stability of local oases. Accordingly, accurately estimating the water use of P. euphratica is important for vegetation protection and water resource allocation. To date, little data are available for evaluating the hysteretic effects between sap flow and environmental variables, and for estimating the water use of desert riparian forest. In this study, we measured the sap flow velocity （Vs） of P. euphratica using the heat ratio method during the growing season of 2012. Based on the response of Vs to solar radiation （R,） and vapor pressure deficit （VPD）, we estimated the hourly Vs and daily Vs using the multivariable linear regression and a modified Jarvis-Stewart （JS） model, respectively. Hysteretic response of Vs to environmental variables was then evaluated using a sap flow model. We found the thresholds of V, responses to Rs and VPD at both hourly and daily scales during the growing season, and successfully estimated the seasonal variations of hourly V, and daily Vs using the JS model. At an hourly scale, the maximum V~ occurred earlier than the maximum VPD by approximately 0.5 h but later than the maximum R, by approximate 1.0 h. At a daily scale, the maximum Vs lagged behind the maximum VPD by approximately 2.5 h while occurred earlier than the maximum Rs by approximately 2 h. However, hysteretic response of V, was weakened when Rs and VPD were measured together using the JS model at both hourly and daily scales. Consequently, short-term and intensive field campaigns, where Vs and environmental variables can be measured, may be used to estimate short-run sap flow and stand transpiration using only two environmental variables.

关键词： sap flow solar radiation vapor pressure deficit Jarvis-Stewart model hysteresis

Patterns,magnitude,and controlling factors of hydraulic redistribution of soil water by Tamarix ramosissima roots

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Journal of Arid Land 2013年第3期5卷 396-407页

作者： TengFei YU Qi FENG jianhua si HaiYang XI Wei LI Research School of Arid Environment and Climate Change Lanzhou University Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Gansu Hydrology and Water Resources Engineering Research Center

Tamarix spp. （Saltcedar） is a facultative phreatophyte that can tolerate drought when groundwater is not accessed. In addition to deep water uptake, hydraulic redistribution （HR） is another factor contributing to the drought tolerance of Tarnarix spp. In this study, data on soil volumetric moisture content （0）, lateral root sap flow, and relevant climate variables were used to investigate the patterns, magnitude, and controlling factors of HR of soil water by roots of Tamarix ramosissima Ledeb. in an extremely arid land in Northwest China. Results showed evident diurnal fluctuations in 0 at the depths of 30 and 50 cm, indicating ＂hydraulic lift＂（HL）. 0 increased remarkably at 10 and 140 cm but decreased at 30 and 50 cm and slightly changed at 80 cm after rainfall, suggesting a possible ＂hydraulic descent＂（HD）. However, no direct evidence was observed in the negative flow of lateral roots, supporting HR （including HL and HD） of T. ramosissima. The HR pathway unlikely occurred via lateral roots; instead, HR possibly occurred through adventitious roots with a diameter of 2-5 mm and a length of 60-100 cm. HR at depths of 20-60 cm ranged from 0.01-1.77 mm/d with an average of 0.43 mm/d, which accounted for an average of 22% of the estimated seasonal total water depletion at 0-160 cm during the growing season. The climate factors, particularly vapor pressure deficit and soil water potential gradient, accounted for at least 33% and 45% of HR variations with depths and years, respectively. In summary, T. ramosissima can be added to the wide list of existing species involved in HR. High levels of HR may represent a considerable fraction of daily soil water depletion and substantially improve plant water status. HR could vary tremendously in terms of years and depths, and this variation could be attributed to climate factors and soil water potential gradient.

关键词： drought tolerance phreatophyte hydraulic redistribution root sap flow Tamarix ramosissima

Comparable water use of two contrasting riparian forests in the lower Heihe River basin, Northwest China

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Journal of Forestry Research 2018年第5期29卷 1215-1224页

作者： Tengfei Yu Qi Feng jianhua si Xiaoyou Zhang Haiyang Xi Chunyan Zhao Alxa Desert Eco-hydrology Experimental Research Station Northwest Institute of Eco-Environment and ResourcesChinese Academy of Sciences Lanzhou 730000 China Key Laboratory of Eco-hydrology of Inland River Basin Chinese Academy of Sciences Lanzhou 730000 China Gansu Hydrology and Water Resources Engineering Research Center Lanzhou 730000 China

Understanding forest ecosystem evapotranspiration（ET） is crucial for water-limited environments,particularly those that lack adequate quantified data such as the lower Heihe River basin of northwest China which is primarily dominated by Tamarix ramosissima *** Populus euphratica ***,we selected the growing season for 2 years （2012 and 2014） of two such forests under similar meteorological conditions to compare ET using the eddy covariance（EC） *** the growing seasons,daily ET of *** ranged from 0.3 to 8.0 mm day^（-1） with a mean of 3.6 mm day^（-1）,and daily ET of *** ranged from 0.9 to 7.9 mm day^（-1） with a mean of 4.6 mm day^（-1） for a total of 548 and 707 mm,*** significantly higher ET of the *** stand was directly linked to high soil evaporation rates under sufficient water availability from *** the soil evaporation was disregarded,water use was comparable to two contrasting riparian forests,a *** forest with a total transpiration of 465 mm and a *** forest with 473 *** analysis demonstrated that climate factors accounted for at least 80% of ET variation in both forest *** conclusion,water use of the riparian forests was low and comparable in this arid region,that suggest the long-term plant adaptation to the local climate and conditions of water availability.

关键词： Eddy covariance Evapotranspiration Heihe River basin Riparian forest

Nighttime transpiration of Populus euphratica during different phenophases

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Journal of Forestry Research 2019年第2期30卷 435-444页

作者： Chunyan Zhao jianhua si Qi Feng Tengfei Yu Peidu Li Michael A.Forster Northwest Institute of Eco-Environment and Resources Chinese Academy of Sciences University of Chinese Academy of Sciences Key Laboratory of Ecohydrology of Inland River Basin Chinese Academy of Sciences School of Agriculture and Food Science The University of Queensland

Evidence exists of nighttime transpiration and its potential impact on plant/water relations for species in a diversity of ecosystems. However, relevant data related to typical desert riparian forest species remains limited Accordingly, we measured sap flow velocity of Populus euphratica using the heat ratio method between 2012 and2014. Nocturnal stem sap flow was separated into nighttime and stem refilling using the ‘‘forecasted refilling''method. Nighttime transpiration was observed for each phenophase. The highest value was during the full foliation period but lowest during leaf expansion and defoliation periods. The contribution of nighttime transpiration to daytime transpiration was an average of 15% but this was comparatively higher during the defoliation period. Relationships between nighttime transpiration, vapor pressure deficits, and air temperatures were more closely associated than with wind speed in all phenophases. Moreover, we found that nighttime transpiration linearly correlated to vapour pressure deficit during the first and the full foliation periods, but nighttime transpiration showed exponential correlations to air temperatures during the same phenophases. Additionally, environmental drivers of transpiration were significantly different between nighttime and daytime(P \ 0.05). Driving forces behind nighttime transpiration were characterized by many factors, and integrated impacts between these multiple environmental factors were complex. Future studies should focus on these integrated impacts on nighttime transpiration, and the physiological mechanisms of nighttime transpiration should be investigated, given that this could also influence its occurrence and magnitude during different phenophases.

关键词： Sap flow Nighttime transpiration Phenophase Heat ratio method Populus euphratica

Non-growing season soil CO_2 efflux and its changes in an alpine meadow ecosystem of the Qilian Mountains,Northwest China

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Journal of Arid Land 2013年第4期5卷 488-499页

作者： ZongQiang CHANG XiaoQing LIU Qi FENG ZongXi CHE HaiYang XI YongHong SU jianhua si Alashan Desert Eco-hydrology Experimental Research Station Cold and Arid Regions Environmental and Engineering Research InstituteChinese Academy of Sciences Gansu Hydrology and Water Resources Engineering Center Academy of Water Resource Conservation Forests in Qilian Mountains of Gansu Province

Most soil respiration measurements are conducted during the growing *** tundra and boreal forest ecosystems,cumulative,non-growing season soil CO2 fluxes are reported to be a significant component of these systems＇ annual carbon ***,little information exists on soil CO2 efflux during the non-growing season from alpine ***,comparing measurements of soil respiration taken annually versus during the growing season will improve the accuracy of estimating ecosystem carbon budgets,as well as predicting the response of soil CO2 efflux to climate *** this study,we measured soil CO2 efflux and its spatial and temporal changes for different altitudes during the non-growing season in an alpine meadow located in the Qilian Mountains,Northwest *** experiments on the soil CO2 efflux of alpine meadow from the Qilian Mountains were conducted along an elevation gradient from October 2010 to April *** measured the soil CO2 efflux,and analyzed the effects of soil water content and soil temperature on this *** results show that soil CO2 efflux gradually decreased along the elevation gradient during the non-growing *** daily variation of soil CO2 efflux appeared as a single-peak *** soil CO2 efflux was low at night,with the lowest value occurring between 02：00-06：***,values started to rise rapidly between 07：00-08：30,and then descend again between 16：00-18：*** peak soil CO2 efflux appeared from 11：00 to 16：*** soil CO2 efflux values gradually decreased from October to February of the next year and started to increase in ***-growing season Q10 （the multiplier to the respiration rate for a 10℃ increase in temperature） was increased with raising altitude and average Q10 of the Qilian Mountains was generally higher than the average growing season Q10 of the Heihe River ***,non-growing season soil CO2 efflux was relatively high in October and early spring and low in the *** soil CO2

关键词： non-growing season soil CO2 efflux spatial and temporal variation alpine meadow Q10 values Qilian Mountains

Using the concept of ecological groundwater level to evaluate shallow groundwater resources in hyperarid desert regions

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Journal of Arid Land 2012年第4期4卷 378-389页

作者： Qi FENG JiaZhong PENG JianGuo LI HaiYang XI jianhua si Alashan Desert Eco-hydrology Experimental Research Station Cold and Arid Regions Environmental and Engineering Research InstituteChinese Academy of SciencesLanzhou 730000China Department of Geography Shaanxi Normal UniversityXi’an 710062China Gansu Hydrology and Water Resources Engineering Center Lanzhou 730000China

This paper, based on the analysis and calculation of the groundwater resources in an arid region from 1980 to 2001, put forward the concept of ecological groundwater level threshold for either salinity control or the determination of ecological warning. The surveys suggest that soil moisture and soil salinity are the most important environmental factors in determining the distribution and changes in vegetation. The groundwater level threshold of ecological warning can be determined by using a network of groundwater depth observation sites that monitor the environmental moisture gradient as reflected by plant physiological characteristics. According to long-term field observations within the Ejin oases, the groundwater level threshold for salinity control varied between 0.5 m and 1.5 m, and the ecological warning threshold varied between 3.5 m and 4.0 m. The quantity of groundwater re- sources （renewable water resources, ecological water resources, and exploitable water resources） in arid areas can be calculated from regional groundwater level information, without localized hydrogeological data. The concept of groundwater level threshold of ecological warning was established according to water development and water re- sources supply, and available groundwater resources were calculated. The concept not only enriches and broadens the content of groundwater studies, but also helps in predicting the prospects for water resources development.

关键词： evaluation water resources Ejin oasis ecological groundwater level groundwater level threshold of ecologicalwarning

Ecophysiological responses to drought stress in Populus euphratica

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Research in Cold and Arid Regions 2021年第4期13卷 326-336页

作者： ChunYan Zhao jianhua si Qi Feng TengFei Yu Huan Luo Jie Qin Northwest Institute of Eco-Environment and Resources Chinese Academy of SciencesLanzhouGansu 730000China Key Laboratory of Ecohydrology of Inland River Basin Chinese Academy of SciencesLanzhou Gansu 730000China University of Chinese Academy of Sciences Beijing 100049China

Ecophysiological responses to drought stress of Populus euphratica in Alashan Desert Eco-hydrology Experimental Research Station were *** show that under mild and moderate drought stress,stomatal length,aperture,area and density is likely to decrease in the early days,but afterwards this is likely to recovery with treatment over the pas‐sage of treatment *** severe drought stress,these properties appear to decline ***,after 45 days of drought-stress treatment,the decline is not as noticeable as before,indicating that Populus euphratica could possibly reduce water evaporation by shutting down the stoma,leading to an improvement in its water use efficiency with better survival under drought stress *** leaf area first decreases,and then increases under mild and moderate drought stress conditions,with the average values under different degree of stress found to be approximately 129.52,120.08,116.63 and 107.28 cm2,*** moderate stress conditions,the leaf water potential appears to show a continuous decline where the average values under different degree of stress are found to be-1.27,-1.85,-4.29 and-4.80 MPa,*** terms of proline content,the results demonstrate that this factor appears to increase significant‐ly under moderate and severe drought stress *** under severe drought stress condition,the content is found to be more than 700μg/*** over average values of 14.64 and 15.90 nmol/g under moderate and severe drought stress,respectively,Malondialdehyde content is found to increase quite rapidly under moderate and severe drought stress conditions at first,which then appears to decrease gradually with the treatment over time.

关键词： stomatal morphology drought stress Malondialdehyde proline Populus euphratica

How changes of groundwater level affect the desert riparian forest ecosystem in the Ejina Oasis,Northwest China

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Research in Cold and Arid Regions 2019年第1期11卷 62-80页

作者： HaiYang Xi JingTian Zhang Qi Feng Lu Zhang jianhua si TengFei Yu Key Laboratory of Ecohydrology of Inland River Basin Institute of Eco-Environment and Resources Chinese Academy of Sciences Alashan Desert Eco-hydrology Experimental Research Station University of Chinese Academy of Sciences CsiRO Land and Water Flagship

Groundwater is a key factor controlling the growth of vegetation in desert riparian systems. It is important to recognise how groundwater changes affect the riparian forest ecosystem. This information will not only help us to understand the ecological and hydrological process of the riparian forest but also provide support for ecological recovery of riparian forests and water-resources management of arid inland river basins. This study aims to estimate the suitability of the Water Vegetation Energy and Solute Modelling(WAVES) model to simulate the Ejina Desert riparian forest ecosystem changes,China, to assess effects of groundwater-depth change on the canopy leaf area index(LAI) and water budgets, and to ascertain the suitable groundwater depth for preserving the stability and structure of desert riparian forest. Results demonstrated that the WAVES model can simulate changes to ecological and hydrological processes. The annual mean water consumption of a Tamarix chinensis riparian forest was less than that of a Populus euphratica riparian forest, and the canopy LAI of the desert riparian forest should increase as groundwater depth decreases. Groundwater changes could significantly influence water budgets for T. chinensis and P. euphratica riparian forests and show the positive and negative effects on vegetation growth and water budgets of riparian forests. Maintaining the annual mean groundwater depth at around 1.7-2.7 m is critical for healthy riparian forest growth. This study highlights the importance of considering groundwater-change impacts on desert riparian vegetation and water-balance applications in ecological restoration and efficient water-resource management in the Heihe River Basin.

关键词： groundwater changes desert riparian forest Ejina Oasis WAVES leaf area index(LAI) water budgets

Evapotranspiration of a Populus euphratica Oliv. forest and its controlling factors in the lower Heihe River Basin,Northwest China

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Research in Cold and Arid Regions 2017年第2期9卷 175-182页

作者： TengFei Yu Qi Feng jianhua si XiaoYou Zhang ChunYan Zhao Alax Desert Eco-hydrology Experimental Research Station Northwest Institute of Eco-Environment and Resources Chinese Academy of Sciences Lanzhou Gansu 730000 China Key Laboratory of Eco-hydrology of Inland River Basin Chinese Academy of Sciences Lanzhou Gansu 730000 China Gansu Hydrology and Water Resources Engineering Research Center Lanzhou Gansu 730000 China

Evapotranspiration (ET) within an ecosystem is crucial for die water-limited environment that currently lacks adequate quantification in the arid region of Northwest China, mainly covered by phreatophytes, such as the Populus euphratica Oliv. tree and the Tamarix ramosissima Ledeb. shrub species. Accordingly. ET was measured for an entire year using eddy covariance (EC) in P. euphratica stands in the lower Heihe River Basin, Northwest China. During the growing season, the total ET was 850 mm, with a mean of 4.0 mm/d, Which is obviously more than that observed at tree-level and stand level scales, which was likely due to the different level of soil evaporation induced by irrigation via water conveyance. Factors associated with ET fall into either environmental or plant eco-physiological categories. Environmental factors account for at least 79% variation of ET and the linear relationship between ET and the voundwater table (GWT) revealed the potential water use of P. euphratica forests under the non-water stress condition with die GWT less than 3 m deep. Plant eco-physiological parameters, specifically die leaf area 'index (LAI), have direct impact on the seasonal pattern of ET which provides a valuable reference to the wide-area estimates of ET for riparian forests by using LAI. In conclusion, P. euphratica forests have high water use after water conveyance, which may be the result of long-term adapting to local climates and limited water availability.

关键词： evapotranspiration eddy covariance Populus euphratica Oliv. forest Bei he River Basin