牦牛粪沉积下高寒草甸植物群落种间关联研究

植物群落构成和种间关联,反映物种在空间上的分布及相互依存和制约关系。为探究牦牛粪沉积和植被斑块互作下草地植物群落演变趋势及稳定性机制,以青藏高原东北缘高寒草甸禾草/杂类草斑块和嵩草/杂类草斑块为对象,分析牦牛粪沉积下两种斑块中主要植物种的重要值(IV)、Jaccard种间关联指数和Spearman秩相关系数的变化规律。结果表明,1)粪沉积使禾草/杂类草斑块的建群种扁穗冰草的IV增加和西北针茅的IV降低,嵩草/杂类草斑块的建群种线叶嵩草的IV降低;2)禾草/杂类草斑块中,粪沉积(DP)和对照(CK)的正负关联种对比为0.61和0.63,显著联结种对为6.6%和6.4%;嵩草/杂类草斑块中,DP和CK的正负关联种对比为0.90和0.72,显著联结种对为2.8%和14.5%;且二者显著联结的种对多存在于优势种或亚优势种与伴生种之间;3)两种斑块中多数种对间联结性弱,群落处于不稳定阶段;粪沉积使嵩草/杂类草斑块的稳定性增强,利于禾草/杂类草斑块的演变;4)依据优势种对环境的适应方式和主导生态因子,将两种斑块的群落植物种划分为喜阳耐旱植物、喜阴喜湿植物和喜阳喜湿植物三大生态种组。

Interspecific associations in plant communities under yak dung depositions in an alpine meadow

Plant community composition and interspecific associations reflect inter-dependence and competition between species,influencing their spatial distribution.To explore the evolutionary trends and stability mechanisms of grassland communities influenced by the interaction between yak dung depositions and vegetation we analyzed the importance values (Ⅳ) of different species,Jaccard association indices and Spearman rank correlation coefficients of the main species present in patches of grass/forb and Kobresia/forb swards under yak dung deposition in an alpine meadow on the northeast Qinghai-Tibetan Plateau.The results indicated that:1) dung deposition (DP) increased the Agropyron cristatum Ⅳ and decreased the Stipa krylovii Ⅳ in grass/forb patches,while decreasing the Kobresia capillifolia Ⅳ for Kobresia/forb parches;2) in grass/forb patches,the species-pairs ratios of positive and negative associations under DP and control (CK) were 0.61 and 0.63,respectively and their respective associated species-pairs were 6.6 ％ and 6.4％.For Kobresia/forb patches,the species-pairs ratio of positive and negative associations in DP and CK were 0.90 and 0.72,respectively and their respective associated species-pairs were 2.8％ in DP and 14.5％ in CK,exhibited mainly between the dominant or sub-dominant species and the companion species;3) the interspecific association of most species-pairs was weak in both vegetation types;yak dung strengthened the stability of Kobresia/forb patches benefiting the generation of grass/forb patches;4) according to their adaptability to environment and the key ecological factors affecting plants,the main plant species of two patches were divided into three ecological groups:shade-intolerant and drought-tolerant plants,shade-tolerant and drought-intolerant plants,and,shade-intolerant and drought-intolerant plants.