摘要:采用野外样方调查和室内分析法，探讨了青藏高原不同退化程度高寒草原和高寒草甸植被群落结构、植物多样性、地上-地下生物量、根系分配及土壤理化特性差异。研究表明：（1）随着退化程度加剧，高寒草原禾草优势地位未改变，高寒草甸优势种莎草逐渐被杂类草取代。（2）随着退化程度加剧，高寒草原地上生物量显著降低（P<0.05），高寒草甸地上生物量先保持稳定再下降。高寒草甸地下生物量较高寒草原地下生物量对退化响应更敏感。（3）高寒草原退化过程中，莎草地上物生量变化不明显（P>0.05），禾草地上生物量贡献率由88.12%减少至53.54%，杂类草地上生物量贡献率由0.08%增加至42.81%；高寒草甸退化过程中，禾草和杂类草地上生物量先增加后减小，莎草地上生物量占比由69.15%减少至0.04%，杂类草地上生物量占比由12.56%增加至92.61%。（4）随着退化程度加剧，高寒草原根系向浅层迁移，高寒草甸根系向深层迁移。（5）退化对高寒草甸土壤含水量（θ）、土壤有机碳（SOC）、总氮（TN）及土壤容重（BD）影响均比高寒草原更强烈。本研究对青藏高原退化草地恢复治理具有重要的参考价值。



Abstract:This study used a field sampling survey and laboratory analysis to investigate the different characteristics of community structure, above/belowground biomass, plant composition and diversity, root proportions in different soil layers, and soil physiochemical properties between alpine steppes and alpine meadows in the Qinghai-Tibetan Plateau. Five degradation stages were identified including non-degradation (ND), light degradation (LD), moderate degradation (MD), severe degradation (SD), and extreme degradation (ED). The results are as follows:(1) as degradation level increased, graminoid dominance in alpine steppes remained unchanged, but sedges in alpine meadows were gradually replaced by the subdominant forb species. (2) With increased alpine steppe degradation, there was a significant decrease in aboveground biomass (P<0.05). The grassland degradation did not affect significantly aboveground biomass with the exception of ED alpine meadows (P<0.05). The response of underground biomass to degradation in alpine meadows was more sensitive compared with alpine steppes. (3) The aboveground sedge biomass exhibited invisible trends with the increase of alpine steppe degradation. The proportion of aboveground graminoid biomass decreased from 88.12% (ND) to 53.54% (ED), while that of forbs increased from 0.08% (ND) to 42.81% (ED). In the process of the ecological succession of alpine meadow degradation, the aboveground graminoid and forb biomass significantly increased except a decrease in ED areas. The contribution of aboveground sedge biomass decreased from 69.15% (ND) to 0.04% (ED), while that of forbs increased from 12.56% (ND) to 92.61% (ED). (4) The alpine steppe root systems showed the increased shallowness as degradation levels increased. However, the alpine meadows showed an opposite trend. (5) The study determined that soil water content (θ), soil organic carbon (SOC), total nitrogen (TN), and bulk density (BD) of alpine meadows were more intensively influenced by degradation compared to those of alpine steppes. The results could provide a valuable reference for the restoration of the degraded grassland in the Qinghai-Tibetan Plateau.





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