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田晓晖,张立锋,张翔,陈之光,赵亮,李奇,唐艳鸿,古松.三江源区退化高寒草甸蒸散特征及冻融变化对其的影响.生态学报,2020,(16).http://dx.doi.org/10.5846/stxb201909151910  
三江源区退化高寒草甸蒸散特征及冻融变化对其的影响
Evapotranspiration characteristics of degraded meadow and effects of freeze-thaw changes in the Three-River Source Region
投稿时间:2019-09-15  修订日期:2020-04-25
DOI: " target="_blank" title="转向doi官网查询:http://dx.doi.org">10.5846/stxb201909151910
关键词        
Key Words        
基金项目国家自然科学基金项目(面上项目,重点项目,重大项目);,省、部研究计划基金
作者单位E-mail
  tianxiaohui_a@163.com 
   
   
   
   
   
   
  songgu@nankai.edu.cn 
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摘要:
蒸散(ET)是陆地生态系统水分收支的重要分量。为探究三江源区退化高寒草甸的蒸散特征,本研究基于2016和2017年涡度相关和微气象系统的观测数据,定量研究了其生态系统的蒸散变化及其环境和生物因子的影响。为深入探讨不同时段的蒸散变化,根据土壤冻融状态和植被生长状况进一步将年蒸散划分为三个时段:冻结期、冻融交替期和消融期,其中在消融期中又划分出植物生长季(5 – 9月),并探讨了土壤冻融对年蒸散量的影响。结果表明:研究区2016和2017年的降水量分别为451.8 mm和442.3 mm,但2017年ET为485.6 mm,明显高于2016年的428.6 mm,两年ET的季节变化趋势相同,ET的最高值出现在生长旺季的7-8月,最低值出现在12月或1月,生长季ET分别占全年ET的73%和72%。2017年的冻结期和冻融交替期比2016年分别减少了8 d,2017年消融期的蒸散量比2016年增加了63.1 mm,其中生长季的蒸散量多36.3 mm。2016和2017年消融期的日蒸散速率分别为1.81和1.97 mm d-1,其中生长季为2.05 mm d-1和2.29 mm d-1,冻融交替期分别为0.97和0.73 mm d-1,而冻结期最低,分别为0.27 mm d-1和0.33 mm d-1。逐步回归分析结果表明:2016年净辐射(Rn)对ET的影响最大,其次是气温(Ta)和土壤含水量(SWC5);2017年ET主要受Rn和Ta的影响。生长季和消融期的冠层导度(gc)和解耦系数(?)明显高于其他两个时段,且2017年gc和?值均高于2016年同期。本研究说明,由于辐射、温度等引起的冻融时间变化和植被的年际间差异,导致三江源区退化草甸各时段及年蒸散量出现明显的变化,该研究结果为全面探讨三江源区蒸散特征提供了参考。
Abstract:
Evapotranspiration (ET) is an important component of terrestrial ecosystem water balance. To examine the ET characteristics of degraded meadow in the Three-River Source Region (TRSR), we quantitatively studied the variation of ecosystem ET and the effect of environmental and biological factors on ET with eddy covariance and micrometeorological measurements from 2016 to 2017. To further characterize the ET at different stages, each year was divided into three periods based on soil temperature: i.e. frozen period, freeze–thaw period, and thawed period. The growing season was further defined as from May to September within the thawed period according to plant growth status. We also explored the influence of soil freeze–thaw on annual ET. The results showed that the annual precipitation in 2016 and 2017 was 451.8 mm and 442.3 mm, respectively, but the amount of annual ET in 2017 (485.6 mm) was obviously higher than that in 2016 (428.6 mm). The seasonal variation of ET showed a similar pattern for two years, with the peak value in July – August and the lowest value in December or January, and the amount of ET in the growing season accounted for about 72% and 73% of annual ET, respectively. The length of frozen and freeze–thaw periods in 2017 was 8 days shorter than those in 2016, while the amount of ET during the thawed period in 2017 was 63.1 mm more than that in 2016, of which the growing reason was 36.3 mm higher. The average daily rate of the ET was 1.81 and 1.97 mm d-1 in thawed period, 2.05 mm d-1 and 2.29 mm d-1 in the growing season, 0.97 and 0.73 mm d-1 in the freeze–thaw period, and the lowest rate was in frozen periods with only 0.27 mm d-1 and 0.33 mm d-1 for 2016 and 2017, respectively. The results of multiple stepwise regression analysis showed that net radiation (Rn) had the greatest impact on ET, and then was the temperature (Ta) and soil water content (SWC5) in 2016, while ET was mainly controlled by Rn and Ta in 2017. The canopy conductance (gc) and decoupling coefficient (?) in the growing season and thawed period were obviously higher than those in other two periods, and the value of both gc and ? in 2017 was higher than those of the same period in 2016. Our study suggested that the obvious variations in ET for each period and year might be caused by the change of freeze–thaw cycle occurrence and different vegetation status due to different radiation and temperature. The results of this study can provide a reference for comprehensively exploring the characteristics of evapotranspiration in the TRSR.

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