Abstract:

exposing the vertical spatial variation of soil nutrients in degraded alpine grassland in the area of the headstream of Yellow River can provide more information about ecological managements of degraded grassland in different regions of the source of the Yellow River. This study mainly focused on three different typical sample area of alpine meadows: transient seasonally frozen soil areas (Dosong, Henan), longer seasonally frozen soil areas (Dawu, Maqin), and permafrost areas (Huashixia, Maduo), in each sample area, 3 small watersheds were selected to collect soil samples of the undisturbed soil layer and determine the nutrient content. This research revealed that, (1) the thickness of soil layer in the transient seasonal permafrost region, longer seasonal permafrost region and permafrost region was (151.67±14.43) cm, (155.33±5.03) cm and (88.33±7.37) cm, respectively. (2) After degrading, the soil pH of 0-20 cm increased in the transient seasonal frozen soil area, the rest had no obviously change. (3) Soil organic matter content decreased significantly with grassland degradation level, and the most sharp decline was in the transient seasonal permafrost region. Therefore, protecting the grassland in the transient seasonal permafrost region has more efficiency to improve of carbon accumulation and carbon sink function. (4) The content of soil alkali hydrolyzable nitrogen decreased gradually with the increase of soil depth and altitude. The content of soil alkali hydrolyzable nitrogen in 0-20 cm soil of non-degraded grassland, the transient seasonal permafrost region, the longer seasonal permafrost region and permafrost region was 1.58, 1.11 and 1.15 times higher than that in the degraded grassland, respectively. The distribution of ammonium and nitrate nitrogen was non-significant. (5) Soil available phosphorus increased with the transient seasonal permafrost region, the content of soil available phosphorus in the surface soil of the non-degraded grassland in the longer seasonal permafrost region was higher than that in the non-degraded grassland, and the content of soil available phosphorus in the degraded grassland in the permafrost region was higher than that in the non-degraded grassland. The variation of soil nutrition characteristics in the process of grassland degradation are different in transient seasonal permafrost region, longer altitude seasonal permafrost region and permafrost region, what’s more the organic matter content is more sensitive with the grassland degradation. Therefore, the ecological environment of alpine grasslands in the source of the Yellow River in the restoration process, the degraded alpine meadow in the transient seasonal permafrost region should be taken into consideration firstly.

Key words: the source region of the Yellow River, grassland degradation, soil nutrient, variation characteristics, permafrost, alpine meadow

摘要：

研究黄河源退化高寒草地土壤养分垂直空间变异,为黄河源退化草地治理提供参考。在黄河源选取短暂季节性冻土区（河南县多松乡）、较长季节性冻土区（玛沁县大武镇）、多年冻土区（玛多县花石峡镇）3个高寒草甸样区,每个样区选取3个小流域采集原状土层土壤样品并测定养分含量。结果表明：（1）短暂季节性冻土区、较长季节性冻土区和多年冻土区土层厚度分别为 (151.67±14.43)、(155.33±5.03) 和 (88.33±7.37) cm;（2）草地退化后,除短暂季节性冻土区0—20 cm土壤pH升高,其他区域变化不明显;（3）土壤有机质含量随着草地退化而显著降低,短暂季节性冻土区降低减少程度最明显,因此,保护短暂季节性冻土区草地更有利于碳积累和碳汇功能提升;（4）土壤碱解氮含量随土层深度加深和海拔升高而逐渐减少,短暂季节性冻土区、较长季节性冻土区和多年冻土区未退化草地0—20 cm土壤碱解氮含量分别是退化草地的1.58、1.11、1.15倍,铵态氮与硝态氮含量分布规律不明显;（5）短暂季节性冻土区草地退化后土壤速效磷含量有所增加,较长季节性冻土区未退化草地表层土壤中速效磷含量较退化草地表层土壤高,多年冻土区草地退化区域土层中土壤速效磷含量较未退化区域高;（6）随着土层深度增加土壤速效钾含量逐渐减少,同一土层中土壤速效钾含量变化规律表现为短暂季节性冻土区>较长季节性冻土区>多年冻土区。短暂季节性冻土区、较长季节性冻土区和多年冻土区草地退化过程中土壤养分变异特征有所不同,其中有机质含量对草地退化的敏感度最高。因此,在黄河源高寒草地生态修复中应首先治理短暂季节性冻土区的退化高寒草甸。

关键词: 黄河源, 草地退化, 土壤养分, 变异特征, 冻土区, 高寒草甸