高寒草甸草地退化对土壤水热性质的影响及其环境效应

doi:10.7522/j.issn.1000-694X.2015.00088

摘要/Abstract

摘要：

青藏高原高寒草甸草地的大面积退化,将改变浅层土壤的水热性质,影响地表水热交换,甚至导致区域生态环境的变化。本文通过系统分析典型原生高寒草甸与中度退化高寒草甸的植物群落特征、地上地下生物量和土壤理化特征的差异,研究高寒草甸草地退化对土壤水热性质的影响及其环境效应。结果表明:随着高寒草甸草地退化,植被覆盖度显著降低(p<0.01),适应旱生、深根系的杂草侵入适应湿润生境、浅根系的以莎草科植物为主的原生植被,生物多样性显著增加(p<0.01);草毡表层(0～10 cm)地下生物量显著减少(p<0.01),30～50 cm地下生物量显著增加(p<0.01)。草毡表层变薄降低了土壤容重的垂向异质性,使表层土壤容重显著增加(p<0.01),土壤颗粒显著变粗(p<0.01)。受浅层土壤有机质降低和土壤容重增加的影响,中度退化高寒草甸土壤的持水量和饱和导水率降低,土壤导热率升高。高寒草甸草地植被退化,土壤持水量、饱和导水率降低和导热率增加将加速地表水热交换,对高寒草甸草地退化和下伏多年冻土消融都可能是正反馈。

关键词: 草地退化, 草毡表层, 地下生物量, 土壤持水量, 土壤导水率, 土壤导热率, 环境效应

Abstract:

Widely distributed degradation of alpine meadow in the Qinghai-Tibet Plateau changes water retention capacity, hydraulic conductivity, and thermal conductivity in the shallow soil layer, which could affect surface water and heat fluxes and feedback to regional ecological environment. We compared plant community characteristics, above and underground biomass, and soil physical and chemical properties between typical native and moderately degraded alpine meadow to understand the effect of land degradation on soil thermal and hydraulic properties and environment. The results showed that vegetation coverage reduced significantly (p<0.01) in moderately degraded alpine meadow. Forbs with deep roots replaced the native sedges which have shallow roots to ensure the ecosystem acclimate the drier environment. Under moderate degradation, biodiversity of alpine meadow ecosystem significantly increased (p<0.01). Underground biomass in mattic epipedon (0-10 cm) significantly decreased (p<0.01), however, it significantly increased (p<0.01) in 30-50 cm soil layer. Mattic epipedon thinning decreased vertical heterogeneity in soil bulk density, and bulk density of surface soil significantly increased (p<0.01). The soil tended to coarsen with degradation (p<0.01). Surface soil water retention capacity and saturated hydraulic conductivity decreased, and soil thermal conductivity increased in moderately degraded alpine meadow because surface soil organic matter significantly decreased and soil bulk density increased. The results of this research suggest that the grassland degradation in alpine meadow results in decreases in soil water retention capacity and increases in soil thermal conductivity, which could accelerate land surface water and heat exchange. In addition, the decrease in vegetation coverage and mattic epipedon could lead to a potential positive feedback to permafrost thawing and regional climate warming.

Key words: grassland degradation, mattic epipedon, underground biomass, soil water retention capacity, soil hydraulic conductivity, soil thermal conductivity, environmental impacts

中图分类号:

尤全刚, 薛娴, 彭飞, 董斯扬. 高寒草甸草地退化对土壤水热性质的影响及其环境效应[J]. 中国沙漠, 2015, 35(5): 1183-1192.

You Quangang, Xue Xian, Peng Fei, Dong Siyang. Alpine Meadow Degradation Effect on Soil Thermal and Hydraulic Properties and Its Environmental Impacts[J]. JOURNAL OF DESERT RESEARCH, 2015, 35(5): 1183-1192.

参考文献

[1] 潘保田,李吉均.青藏高原:全球气候变化的驱动机与放大器—Ⅲ.青藏高原隆起对气候变化的影响[J].兰州大学学报(自然科学版),1996(1):108-115.
[2] 冯松,汤懋苍.青藏高原是我国气候变化启动区的新证据[J].科学通报,1998(6):633-636.
[3] Klein J A,Harte J,Zhao X Q.Experimental warming causes large and rapid species loss,dampened by simulated grazing,on the Tibetan Plateau[J].Ecology Letters,2004,7(12):1170-1179.
[4] 姚檀栋,朱立平.青藏高原环境变化对全球变化的响应及其适应对策[J].地球科学进展,2006,21(5):459-464.
[5] IPCC.Climate Change 2013:The Physical Science Basis[M].http://www.ipcc.ch/report/ar5/wg1/.
[6] Wang B,Bao Q,Hoskins B,et al.Tibetan Plateau warming and precipitation changes in east Asia[J].Geophysical Research Letters,2008,35:L14702.
[7] Yao T,Pu J,Lu A,et al.Recent glacial retreat and its impact on hydrological processes on the Tibetan Plateau,China,and surrounding regions[J].Arctic,Antarctic, and Alpine Research,2007,39(4):642-650.
[8] Lei Y B,Yao T D,Bird B W,et al.Coherent lake growth on the central Tibetan Plateau since the 1970s:characterization and attribution[J].Journal of Hydrology,2013,483:61-67.
[9] Cheng G D,Wu T H.Responses of permafrost to climate change and their environmental significance,Qinghai-Tibet Plateau[J].Journal of Geophysical Research,2007,112:F02S03.
[10] Wu Q B,Zhang T J.Recent permafrost warming on the Qinghai-Tibetan Plateau[J].Journal of Geophysical Research,2008,113:D13108.
[11] Wang G X,Wang Y B,Li Y S,et al.Influences of alpine ecosystem responses to climatic change on soil properties on the Qinghai–Tibet Plateau,China[J].Catena,2007,70(3):506-514.
[12] Xue X,Guo J,Han B S,et al.The effect of climate warming and permafrost thaw on desertification in the Qinghai-Tibetan Plateau[J].Geomorphology,2009,108:182-190.
[13] Yi S H,Zhou Z Y,Ren S L,et al.Effects of permafrost degradation on alpine grassland in a semi-arid basin on the Qinghai-Tibetan Plateau[J]. Environmental Research Letters,2011,6:045403.
[14] 徐翠,张林波,杜加强,等.三江源区高寒草甸退化对土壤水源涵养功能的影响[J].生态学报,2013,33(8):2388-2399.
[15] 李婧,杜岩功,张法伟,等.草毡表层演化对高寒草甸水源涵养功能的影响[J].草地学报,2012,20(5):836-841.
[16] Zhou H K,Zhao X Q,Tang Y H,et al.Alpine grassland degradation and its control in the source region of the Yangtze and Yellow Rivers,China[J]. Grassland Science,2005,51:191-203.
[17] 周华坤,赵新全,周立,等.青藏高原高寒草甸的植被退化与土壤退化特征研究[J].草业学报,2005,14(3):31-41.
[18] Wang G X,Liu G S,Li C J,et al.The variability of soil thermal and hydrological dynamics with vegetation cover in a permafrost region[J].Agricultural and Forest Meteorology,2012,162:44-57.
[19] 王介民.陆面过程实验和地气相互作用研究—从HEIFE到IMGRASS和GAME-Tibet/TIPEX[J].高原气象,1999,18(3):280-294.
[20] 王长庭,王启兰,景增春,等.不同放牧梯度下高寒小嵩草草甸植被根系和土壤理化特征的变化[J].草业学报,2008,17(5):9-15.
[21] 王根绪,沈永平,钱鞠,等.高寒草地植被覆盖变化对土壤水分循环影响研究[J].冰川冻土,2003,25(6):653-659.
[22] 李春杰,王根绪,任东兴,等.风火山流域土壤入渗特征与环境因子的关系分析[J].水土保持通报,2009,29(6):16-33.
[23] Wang G X,Wang Y B,Li Y S,et al.Influences of alpine ecosystem responses to climatic change on soil properties on the Qinghai-Tibet Plateau,China[J].Catena,2007,70(3):506-514.
[24] 周幼吾,郭东信,邱国庆,等.中国冻土[M].北京:科学出版社,2000:329-353.
[25] 全国土壤普查办公室.中国土壤[M].北京:中国农业出版社,1998:773-804.
[26] Li N,Wang G X,Yang Y,et al.Plant production,and carbon and nitrogen source pools,are strongly intensified by experimental warming in alpine ecosystems in the Qinghai-Tibet Plateau[J].Soil Biology and Biochemistry,2010,43:942-953.
[27] Yang Y H,Fang J Y,Ji C J,et al.Above- and belowground biomass allocation in Tibetan grasslands[J].Journal of Vegetation Science,2009,20(1):177-184.
[28] Agrawal A,Gopal K.Application of Diversity Index in Measurement of Species Diversity[M]//Biomonitoring of Water and Waste Water.Springer India,2013:41-48.
[29] Lü D Q,Shao M A,Horton R,et al.Effect of changing bulk density during water desorption measurement on soil hydraulic properties[J].Soil Science,2004,169(5):1-11.
[30] van Genuchten M T,Leij F J,Yates S R.The RETC code for quantifying the hydraulic functions of unsaturated soils[R].Ada,OK,USA:U.S.Environmental Protection Agency,1991.
[31] 邵明安,王全九,黄明斌.土壤物理学[M].北京:高等教育出版社,2006:47-161.
[32] 温智,盛煜,马巍,等.青藏高原北麓河地区原状多年冻土导热系数的试验研究[J].冰川冻土,2005,27(2):182-187.
[33] 周华坤,周立,赵新全,等.青藏高原高寒草甸生态系统稳定性研究[J].科学通报,2006,51(1):63-69.
[34] 时忠杰,王彦辉,徐丽宏,等.六盘山典型植被下土壤大孔隙特征.应用态学报,2007,18(2):2675-2680.
[35] 曹广民,龙瑞军.放牧高寒嵩草草甸的稳定性及自我维持机制[J].中国农业气象,2009,30(4):553-559.
[36] Jin H J,He R X,Cheng G D,et al.Changes in frozen ground in the Source Area of the Yellow River on the Qinghai-Tibet Plateau,China,and their eco-environmental impacts[J].Environmental Research Letters,2009,4:045206.
[37] Cheng G D,Wu T H.Responses of permafrost to climate change and their environmental significance,Qinghai-Tibet Plateau[J].Journal of Geophysical Research,2007,112:F02S03.
[38] 王大力,尹澄清.植物根孔在生态系统中的功能[J].生态学报,2000,20(5):869-874.
[39] You Q G,Xue X,Peng F,et al.Comparison of ecosystem characteristics between degraded andintact alpine meadow in the Qinghai-Tibetan Plateau,China[J].Ecological Engineering,2014,71:133-143.
[40] Wang G X,Hu H C,Liu G S,et al.Impacts of changes in vegetation cover on soil water heat coupling in an alpine meadow of the Qinghai-Tibet Plateau,China[J].Hydrology and Earth System Sciences,2009,13:327-341.
[41] 吴青柏,沈永平,施斌.青藏高原冻土及水热过程与寒区旱区生态环境的关系[J].冰川冻土,25(3):250-255.
[42] Jin H J,Yu Q H,Wang S L,et al.Changes in permafrost environments along the Qinghai-Tibet engineering corridor induced by anthropogenic activities and climate warming[J].Cold Regions Science and Technology,2008,53:317-333.
[43] 王根绪,李元寿,吴青柏,等.青藏高原冻土区冻土与植被的关系及其对高寒草甸生态系统的影响[J].中国科学:D辑,2006,36(8):743-754.