藏北不同退化阶段高寒草甸植物群落特征与土壤养分特性

为探究藏北不同退化阶段高寒草甸的植物群落特征、土壤养分特性及其相关性,以那曲县那玛切村的轻度退化(lightly degraded,LD)、中度退化(moderately degraded,MD)和重度退化(severely degraded,SD)高寒草甸为研究对象,采用冗余分析(RDA)试图揭示不同退化阶段高寒草甸土壤环境因子与植被因子之间的关系。结果表明:1)研究区植物共有9科20属25种,莎草科、禾本科、菊科和蔷薇科植物适应性较强,不同退化草甸植被类型分别为高山嵩草+斑唇马先蒿,弱小火绒草+高山嵩草,二裂委陵菜+白苞筋骨草,其中高山嵩草是轻、中度退化草甸的优势种,不同退化阶段高寒草甸杂类草均占据重要地位,生活型以多年生草本为主。2)从轻度退化草甸到重度退化草甸,植物群落特征(地上生物量、高度、密度、频度、总盖度)整体呈递减趋势,且差异显著(P<0.05),Shannon-Wiener多样性指数、Margalef物种丰富度指数、Simpson优势度指数、Pielou均匀度指数随着退化加重呈降低的趋势。3)随退化程度加重,土壤有机质、速效氮、全氮、全磷、速效磷、速效钾、全钾均...

Plant community composition and soil nutrient status of degraded alpine meadow sites in Northern Tibet

This research investigated the community features， soil nutrient characteristics and their correlations in different degraded alpine meadows in Northern Tibet. Lightly degraded （LD）， moderately degraded （MD） and severely degraded （SD） alpine meadow sites were selected for study and our research used a combination of field investigation， laboratory measurement， variance analysis and redundancy analysis to elucidate the relationships between vegetation ecological characteristics and soil environmental factors for these three different alpine meadow degradation stages in Northern Tibet. It was found that： 1） There were 25 plant species from 20 genera and nine families present in the study area， and these were species with strong ecological adaptability， mainly from the in Cyperaceae， Poaceae， Asteraceae and Rosaceae families. Species associations commonly present across these alpine meadow sites included Kobresia pygmaea with Pedicularis longiflora， Leontopodium pusillum with K. pygmaea and Potentilla bifurca with Ajuga lupulina. Among these， K. pygmaea was the dominant species at LD and MD sites， although the functional groups were dominated by forbs. The perennial herb is the major vegetation component in Northern Tibet. 2） The characteristics of the studied plant communities， including aboveground biomass， height， density， frequency and vegetation cover showed a decreasing trend from LD to SD （P<0.05）. And the species Margalef index， Pielou index， Simpson index and Shannon-Wiener index of the LD sites had the highest values. 3） With increasing alpine meadow degradation， organic matter， total nitrogen， total phosphorus， total potassium， available nitrogen， available phosphorus and available potassium all decreased， while pH increased. 4） Species diversity index and the available phosphorus and total phosphorus across the series of degradation stages were significantly positively correlated. The aboveground biomass showed significantly positive correlations with total nitrogen. The factors contributing most strongly to vegetation growth in these alpine meadows at different stages of degradation were available nitrogen， organic matter and pH， respectively. This indicated a correlation between the degradation status of alpine meadows， plant community composition and soil nutrient status. In summary， the soil nutrient status， especially the role of soil nitrogen and phosphorus， must be considered when researching and managing alpine meadow degradation．