青藏高原高寒湿地冻融过程土壤温湿变化特征
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摘要
青藏高原高寒湿地作为大江大河支流的发源地,其冻融过程对该地区及下游的生态系统和气候调节有重要意义。利用青藏高原腹地三江源区隆宝高寒湿地试验站的高时间分辨率土壤温湿数据,对冻融过程中土壤温湿的季节、日以及冻融转换期变化特征进行分析和探讨。结果表明:(1)高寒湿地土壤冻融过程中,土壤温度整体表现出夏高冬低的变化特征,冻结期5 cm、40 cm、20 cm、30 cm和10 cm地温依次增大,地温随深度变化存在一定的不规律性,而非冻结期则正好相反;土壤湿度在冻结期自上而下逐渐降低,融化期自上而下逐渐增加。(2)土壤表层5 cm和深层40 cm地温存在显著的日变化特征,表层较深层变化更显著,且夏季变化幅度最大;土壤含水率较稳定,除表层有一定波动,其他各层无明显日变化。(3)冻融转换期,土壤温度垂直分布存在显著的三层结构,10 cm和30 cm处与邻近层的温度差异是导致这种特殊分布的主要原因;随着深度的加深,土壤含水率冻结期(融化期)逐渐增加(减少),且深层比浅层的变化时间明显滞后。
As the sources of some large rivers,the freeze-thaw process of alpine wetland in Qinghai-Tibetan Plateau is of great importance to regional and downstream ecosystem and climate regulation. Based on soil temperature and moisture observation data at Longbao test station of Yushu prefecture which is located in three rivers source area on Qinghai-Tibetan Plateau,the diurnal and seasonal variation characteristics of soil temperature and water content in the freezing and thawing processes were analyzed,especially during the freezing and thawing conversion period. The results indicate that the soil temperature and water content of alpine wetland had obvious seasonal variations in the freezing and thawing periods. The soil temperature was high in summer and low in winter. The profile values of soil temperature successively increased at 5 cm,40 cm,20 cm,30 cm,10 cm depth during the freezing period. On the contrary,it decreased in sequence at 5 cm,40 cm,20 cm,30 cm and 10 cm depth during the thawing period. The soil water content reduced gradually from top to bottom in the freezing period,while it increased from top to bottom during the thawing period. The soil temperature in surface layer(5 cm) and deep layer(40 cm) in alpine wetland had diurnal variation characteristics,the diurnal variation in surface layer was more significant than that in deep layer,and the variation range was biggest in summer. However,the soil water content was stable in a day except for a certain fluctuation in surface layer. The vertical distribution of soil temperature presented a three-layer structure due to the temperature differences between that at 10 cm,30 cm depth and their adjacent layers during the freeze-thaw transition period,while the soil water content appeared obvious regular changes,it decreased in the freezing period and increased in the thawing period with the increase of depth,and the change of soil water content in deep layer was later than that in shallow layer.
As the sources of some large rivers,the freeze-thaw process of alpine wetland in Qinghai-Tibetan Plateau is of great importance to regional and downstream ecosystem and climate regulation. Based on soil temperature and moisture observation data at Longbao test station of Yushu prefecture which is located in three rivers source area on Qinghai-Tibetan Plateau,the diurnal and seasonal variation characteristics of soil temperature and water content in the freezing and thawing processes were analyzed,especially during the freezing and thawing conversion period. The results indicate that the soil temperature and water content of alpine wetland had obvious seasonal variations in the freezing and thawing periods. The soil temperature was high in summer and low in winter. The profile values of soil temperature successively increased at 5 cm,40 cm,20 cm,30 cm,10 cm depth during the freezing period. On the contrary,it decreased in sequence at 5 cm,40 cm,20 cm,30 cm and 10 cm depth during the thawing period. The soil water content reduced gradually from top to bottom in the freezing period,while it increased from top to bottom during the thawing period. The soil temperature in surface layer(5 cm) and deep layer(40 cm) in alpine wetland had diurnal variation characteristics,the diurnal variation in surface layer was more significant than that in deep layer,and the variation range was biggest in summer. However,the soil water content was stable in a day except for a certain fluctuation in surface layer. The vertical distribution of soil temperature presented a three-layer structure due to the temperature differences between that at 10 cm,30 cm depth and their adjacent layers during the freeze-thaw transition period,while the soil water content appeared obvious regular changes,it decreased in the freezing period and increased in the thawing period with the increase of depth,and the change of soil water content in deep layer was later than that in shallow layer.
引文
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[27]DAOUT S,DOIN M P,PELTZER G,et al.Large-scale In SAR monitoring of permafrost freeze-thaw cycles on the Tibetan Plateau[J].Geophysical Research Letters,2017,44(2):1-10.
[2]罗磊.青藏高原湿地退化的气候背景分析[J].湿地科学,2005,3(3):190-199.
[3]王根绪,李元寿,王一博,等.近40年来青藏高原典型高寒湿地系统的动态变化[J].地理学报,2007,62(5):481-491.
[4]王学佳,杨梅学,万国宁.藏北高原D105点土壤冻融状况与温湿特征分析[J].冰川冻土,2012,34(1):56-63.
[5]宋长春.湿地生态系统对气候变化的响应[J].湿地科学,2003,1(2):122-127.
[6]尚大成,王澄海.高原地表过程中冻融过程在东亚夏季风中的作用[J].干旱气象,2006,24(3):19-22.
[7]崔洋,常倬林,余莲,等.青藏高原春季地表非绝热加热异常对东亚夏季风强度的影响[J].干旱气象,2017,35(1):1-11.
[8]吴青柏,沈永平,施斌.青藏高原冻土及水热过程与寒区生态环境的关系[J].冰川冻土,2003,25(3):250-255.
[9]赵林,程国栋,李述训,等.青藏高原五道梁附近多年冻土活动层冻结和融化过程[J].科学通报,2000,45(11):1205-1210.
[10]刘光生,王根绪,孙向阳,等.长江源区沼泽草甸多年冻土活动层土壤水分对模拟增温的响应[J].冰川冻土,2015,37(3):668-675.
[11]PIAO S L,CIAIS P,HUANG Y,et al.The impacts of climate change on water resources and agriculture in China[J].Nature,2010,467(7311):43-51.
[12]李卫朋,范继辉,沙玉坤,等.藏北高寒草原土壤温度变化与冻融特征[J].山地学报,2014,32(4):407-416.
[13]MA K,ZHANG Y,TANG S X,et al.Spatial distribution of soil organic carbon in the Zoige alpine wetland northeastern QinghaiTibet Plateau[J].Catena,2016,144:102-108.
[14]陈永富,刘华,皱文涛,等.三江源高寒湿地动态变化趋势分析[J].林业科学,2012,48(10):70-76.
[15]潘竟虎,王建,王建华.长江、黄河源区高寒湿地动态变化研究[J].湿地科学,2007,5(4):298-304.
[16]杜际增,王根绪,杨燕,等.长江黄河源区湿地分布的时空变化及成因[J].生态学报,2015,35(18):6173-6182.
[17]张继平,张镱锂,刘峰贵,等.长江源区当曲流域高寒湿地类型划分及分布研究[J].湿地科学,2011,9(3):218-226.
[18]张法伟,刘安花,李英年,等.青藏高原高寒湿地生态系统CO2通量[J].生态学报,2008,28(2):453-462.
[19]王冬雪,高永恒,安小娟,等.青藏高原高寒湿地温室气体释放对水位变化的响应[J].草业学报,2016,25(8):27-35.
[20]张海宏,周秉荣,肖宏斌.高寒草甸和高寒湿地土壤水热特征比较[J].干旱气象,2015,33(5):783-789.
[21]陈渤黎.青藏高原土壤冻融过程陆面能水特征及区域气候效应研究[D].北京:中国科学院大学,2013:7-9.
[22]张强,王胜.干旱荒漠地区土壤水热特征和地表辐射平衡的年变化研究[J].自然科学进展,2007,17(2):211-216.
[23]杨扬,左洪超,王丽娟,等.干旱区荒漠草原过渡带快速变化的陆面过程特征观测分析[J].干旱气象,2015,33(3):412-420.
[24]岳平,张强,赵文,等.黄土高原半干旱草地生长季干湿时段环境因子对陆面水、热交换的影响[J].中国科学:地球科学,2015,45(8):1229-1242.
[25]张强,孙昭萱,王胜.黄土高原定西地区陆面物理量变化规律研究[J].地球物理学报,2011,54(7):1727-1737.
[26]程善俊,黄建平,季明霞,等.中国华北暖季土壤湿度的变化特征[J].干旱气象,2015,33(5):723-731.
[27]DAOUT S,DOIN M P,PELTZER G,et al.Large-scale In SAR monitoring of permafrost freeze-thaw cycles on the Tibetan Plateau[J].Geophysical Research Letters,2017,44(2):1-10.