祁连山高寒草地不同退化程度植物群落结构与物种多样性研究

为祁连山康乐草原生产力恢复与提高提出有效措施、生物多样性保护和资源可持续利用提供理论依据,采用样方法对祁连山高寒草地不同退化程度植物群落结构和土壤特性进行调查、测定和分析,并运用5个多样性指标(Margalef丰富度指数、Dominance优势度指数、Simpson多样性指数、Evenness均匀度指数和Shannon多样性指数)研究了其物种多样性变化。结果表明:1)轻度退化草地(LDG)-中度退化草地(MDG)-重度退化草地(SDG),不同退化草地植物群落特征(密度、高度、频度、总盖度和地上生物量)整体呈现降低趋势且差异显著(P<0.05),表现为LDG>MDG>SDG;2)研究区植物共15科35属39种,其中豆科、蔷薇科、禾本科、菊科和莎草科中的植物均具备较强生态适应性,各退化程度草地植被型分别为草地早熟禾+珠芽蓼、赖草+矮生嵩草、矮生嵩草+赖草,其中禾草是群落的优势种;3)高寒草地功能群植物呈现杂类草最多,禾草类次之,毒草类占有比例最少,其中在不同退化草地杂类草、毒草类重要值分别为75.14%(SDG)>48.67%(LDG)>30.05%(MDG)、20.81%(LDG)>18.01%(SDG)>17.11%(MDG);4)不同退化草地群落物种优势度指数在重度退化草地最高为0.23,而轻度退化草地物种Margalef丰富度指数最高为2.64、Shannon多样性指数最高为2.09;5)随退化程度加重,土壤全磷、全氮、有机质和含水量呈现下降的趋势,pH呈升高的趋势,且不同退化草地土壤环境因子含量对植被生长贡献率不同。综上所述,随着康乐草地退化程度增加群落结构向单一趋势演替且环境限制因子也发生相应变化。

Plant community structure and species diversity differences in alpine grassland in the Qilian Mountains with different levels of degradation

This research aimed to provide a theoretical basis for effective management, productivity improvement, biodiversity protection, and sustainable resource use in the restoration of Kangle grassland in the Qilian Mountains. The plant community structure and soil characteristics at selected sites with different levels of degradation were sampled and analyzed. Five diversity indexes (the Margalef index, Dominance index, Simpson index, Evenness index and Shannon index) were used to explore changes in species diversity. The results showed that: 1) As expected, aboveground biomass, vegetation height and ground cover, plant density, and plant frequency showed a decreasing trend (P<0.05), from lightly degraded grassland (LDG) to moderately degraded grassland (MDG) and from MDG to severely degraded grassland (SDG). 2) There were 39 species, 35 genera and 15 families in the study area. The plant community had strong ecological adaptability, which was mainly represented by the Fabaceae, Rosaceae, Poaceae, Asteraceae and Cyperaceae families. The dominant species of different degradation degrees were: LDG, Poa pratensis and Polygonum viviparum; MDG, Leymus secalinus and Kobresia humilis; SDG, K. humilis and L. secalinus. Poaceae had a key role in the stability of the community. 3) In defining functional groups in alpine grassland, it was found that forb plants were of primary importance, followed by graminoid plants, with harmful grass plants the least important. The importance values of forb plants at differing grassland degradation levels were 75.14% (SDG)>48.67% (LDG)>30.05% (MDG). The importance values of harmful grass plants at differing grassland degradation levels were 20.81% (LDG)>18.01% (SDG)>17.11% (MDG). 4) The highest species Dominance index within the SDG community was 0.23; the highest Margalef richness index of the LDG was 2.64 and the Shannon comprehensive index of the LDG community was 2.09. 5) With increased degree of degradation, the soil total phosphorus, total nitrogen, organic matter and water contents showed downward trends, while pH increased. In summary, with increasing degree of degradation, the change in grassland community structure exhibited a continuous single trend Kangle, while the major environmentally limiting factors changed.