青藏高原'黑土滩'退化草地植物和土壤对秃斑面积变化的响应

摘要

Characteristics and variation of soil and vegetation in and surrounding, 93 bare patches of a typical “black soil patch” area of the Qinghai—Tibetan Plateau were investigated. Bare-patches formed “negative fertile islands” after sod layers breaking off in alpine meadows, i.e. soil nutrients in bare-patches were lower than those in the surroundings. There were obvious differences in total nitrogen, ammonium nitrogen, and organic carbon between the two parts. The pH values of bare patches were higher than those of the surroundings, so meadows lose nutrients in bare patches. If the bare-patch was more than 5 m2 , the heterogeneity was reduced compared with the surroundings. The maximum number of plant species in bare-patches was 20 to 25, considerably lower than that of the grassland covered with a sod layer. The major toxic weeds, Aconitum pendulum and Carum carvi, in the bare-patches had a linear positive correlation with the bare-patch area, and the number of rat holes was also linearly positively related to the bare-patch area.%在青藏高原典型"黑土滩"区对93个秃斑块及周边的土壤和植被特征以及变化规律进行了调查分析.结果表明,高寒草地草毡层消失后形成的"黑土滩"秃斑在草地中形成一个"负肥力岛",秃斑块内土壤养分低于秃斑周边有草皮层覆盖的草地,其中全氮、铵态氮、有机碳差异显著;同时秃斑内pH显著高于秃斑块外水平.秃斑块是草地养分流失的通道.当秃斑面积大于5m2时.秃斑块与周边景观异质性降低.秃斑内植物物种饱和度为20～25种,显著低于有草毡层覆盖的草地.秃斑内主要毒杂草铁棒锤和细裂叶莲蒿与秃斑块面积呈线性正相关.鼠洞个数与秃斑块面积亦呈线性正相关.