三江源典型高寒草地坡面土壤有机碳变化特征及其影响因素

doi:10.11849/zrzyxb.2011.12.007

摘要/Abstract

摘要： 以三江源地区高寒草地退化坡面为研究对象,从草地类型、鼠害和自然因素如水蚀、风蚀、冻融作用这一角度上探讨发生在不同退化程度上土壤有机碳的变化特征,对明晰高寒地区退化草地的碳变化机理和全球气候响应具有重要意义。结果表明:同一侵蚀环境条件和退化程度下,以小嵩草、矮嵩草为优势种高寒草甸比以紫花针茅为优势种的高寒草原土壤有机碳蓄存能力高。轻度退化程度受水蚀影响的高寒草甸曲麻河乡QMH1坡面土壤有机碳平均含量是相距3.5 km高寒草原曲麻河乡QMH2坡面的2.2倍(P<0.01);轻度退化程度受风蚀影响的高寒草甸五道梁WDL坡面土壤有机碳平均含量是高寒草原不冻泉BDQ坡面土壤有机碳含量的3.8倍(P<0.01)。水蚀作用显著影响了高寒退化草地土壤有机碳在坡面上的分布,表现为随坡面向下迁移富集的特征。轻度退化程度受水蚀影响的高寒草甸玛龙ML1号坡面下坡位(距坡顶580 m以下)土壤有机碳平均含量比上坡位(距坡顶580 m以上)高22%(P<0.01)。高寒草甸玛龙ML2坡面土壤有机碳分布特征,不仅具有土壤有机碳含量随退化程度加剧而降低的规律,还叠加有土壤有机碳随水土流失向下富集的迁移分布规律,具体表现为坡上位轻度退化>坡中下位中度退化>坡下位极度退化>坡中上位重度退化,因极度退化坡位处于重度退化的下坡位,表现出极度退化坡位土壤有机碳含量比重度退化坡位高49.3%(P<0.05)。风蚀作用使高寒退化草地表层土壤粗骨化和土壤有机碳加速矿化,表现为受湖陆风影响较弱的鄂陵湖ELH坡面土壤有机碳平均含量比受湖陆风影响较强的扎陵湖ZLH坡面高27.9%(P<0.05)。冻融垮塌降低了高寒退化草地土壤有机碳平均含量,但差异不显著。鼠害影响降低了高寒退化草地土壤有机碳的平均含量,并加速了高寒草地退化的进程。中度退化鼠洞周围SDⅠ—Ⅲ土壤有机碳平均含量是极度退化鼠洞周围SDⅣ—Ⅵ的2.1倍;而未受鼠害影响的中度退化ML2Ⅰ—Ⅱ土壤有机碳平均含量是极度退化ML2Ⅳ—Ⅵ的1.6倍。高寒坡面草地受水蚀、风蚀、冻融以及鼠害等因素作用加剧了土壤有机碳的损失。

关键词: 高寒退化草地, 土壤有机碳, 水蚀, 风蚀, 冻融, 鼠害

Abstract: Exploring the distribution characteristics of soil organic carbon and its influencing factors under different degraded types of alpine slope grasslands was crucial to better understand the changes of soil organic carbon content and responses to global climate change. Two types of alpine grassland (alpine meadow and alpine steppe), and the impact mechanism of soil organic carbon were studied under the influences of external environment, such as water erosion, wind erosion, freezing-thawing erosion and rodent damage in the "Three-River Headwaters" region. The results showed that: the contents of soil organic carbon of alpine meadow dominated by Kobresia pygmaea and Kobresia humilis were higher than alpine steppe dominated by Stipa purpurea Griseb. Under the conditions of the lightly degraded and water erosion, the average content of alpine meadow QMH1 was 2.2 times (P<0.01) of alpine steppe QMH2 which was 3.5 km away from QMH1. And it was similar to the conditions of the lightly degraded and wind erosion, the average content of alpine meadow WDL was 3.8 times (P<0.01) of alpine steppe BDQ. Under the influence of water erosion, the soil organic carbon of alpine grassland was transferred downward along the slope grassland. The soil organic carbon content of lower slope (downward 580 m distance from the top slope ) of alpine meadow ML1 was 22% higher (P<0.05)than the upper slope (upward 580 m distance from the top slope). The overlying distribution characteristics of soil organic carbon for ML2 alpine meadow was performed, not only decreased with the increase of degradation, but also migrated downward along the slope grassland due to water erosion. The soil organic carbon content of extremely degraded grassland, located on the lower slope compared with severely degraded grassland, was 49.3% (P<0.05) higher than severely degraded grassland for ML2 alpine meadow. Wind erosion made rough the soil surface of grassland and accelerated mineralization of soil organic carbon. The average content of soil organic carbon of ELH lightly impacted by lake breeze was 27.9% higher than ZLH (P<0.05) strongly impacted by lake breeze. The soil organic carbon content was reduced by freeze-thaw erosion, but the difference was not significant. Rodent damage not only reduced the content of soil organic carbon, but also accelerated deterioration of grassland, the average content of soil organic carbon of moderate degradation SDⅠ-Ⅲ around the rat holes were 2.1 time of the extremely degraded grassland SDⅣ-Ⅵ; and the average content of soil organic carbon of the moderately degraded grassland ML2Ⅰ-Ⅱ away from rat holes was 1.6 times of the extremely degraded grassland ML2Ⅳ-Ⅵ. The soil organic carbon of alpine slope grassland was aggravated due to influence by wind erosion, water erosion, freeze-thaw and rodent damage.

Key words: alpine degraded grassland, soil organic carbon, water erosion, wind erosion, freeze-thaw erosion, rodent damage

中图分类号:

S153.6

孙文义, 邵全琴, 刘纪远, 肖桐. 三江源典型高寒草地坡面土壤有机碳变化特征及其影响因素[J]. 自然资源学报, 2011, 26(12): 2072-2087.

SUN Wen-yi, SHAO Quan-qin, LIU Ji-yuan, XIAO Tong. The Variation Characteristics of Soil Organic Carbon of Typical Alpine Slope Grasslands and Its Influencing Factors in the "Three-River Headwaters" Region[J]. JOURNAL OF NATURAL RESOURCES, 2011, 26(12): 2072-2087.

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