若尔盖不同生境植物多样性与植物竞争强度和生态位重叠度的关系

植物多样性与植物竞争强度和生态位重叠度的关系会随环境发生变化。为探究上述关系在若尔盖地区的表现形式，于2021年8月对若尔盖地区典型的水生、湿生、湿生-中生和中生植物群落进行调查，构建了新的植物竞争强度（Competition intensity，CI）公式并进行测算，计算了植物群落的植物多样性指数（包括物种丰富度、Shannon-Weiner指数、Simpson指数和Pielou均匀度指数）和生态位重叠度（Niche overlap of species，NOS），分析了植物群落物种多样性指数与CI和NOS的关系。结果表明：1）从水生到中生生境，植物多样性指数均呈增加趋势（P<0.05）；2）湿生-中生生境的CI显著高于湿生生境（P<0.05），湿生生境的NOS高于水生生境（P<0.05）；CI与NOS无显著相关性，但在湿生生境中两者呈倒抛物线关系（P<0.05）。3）整体来看，植物群落的物种丰富度与CI呈抛物线关系（P<0.05），与NOS无显著关系（P>0.05）；Shannon-Weiner指数、Simpson指数和Pielou均匀度指数均与NOS呈线性正相关（P<0.05），与CI无显著关系（P>0.05）；从单个生境看，湿生-中生生境的Simpson指数、Shannon-Weiner指数和Pielou均匀度指数与CI呈线性负相关（P<0.05），其余生境的上述多样性指数与CI无显著关系（P>0.05）；各生境的植物多样性指数均与NOS无显著相关性（P>0.05）。本研究表明，从水生到中生生境，若尔盖地区的植物多样性呈增加趋势，但植物多样性与物种竞争强度和生态位重叠度的关系较复杂。本研究结果有助于理解若尔盖高原植物多样性的形成机制。

Relationship between plant diversity and plant competition intensity and niche overlap across a habitat gradient in Zoige

The relationship between plant diversity and plant competition intensity and niche overlap varies with the environment. To explore this relationship in Zoige, this study investigated typical aquatic, wet, wet-mesic, and mesic plant communities in Zoige in August, 2021. A new method for calculating plant competition intensity (CI) was constructed, and niche overlap of species (NOS) and species diversity indices (including species richness, Shannon-Weiner index, Simpson index, and Pielou index) were also calculated based on field data. Changes in plant diversity indices, CI, NOS, and relationships between these indices were then analysed across the habitat gradient. The results showed that:1) all plant diversity indices tended to increase from aquatic to mesic habitats (P<0.05). 2) The CI of wet-mesic habitat was significantly higher than that of wet habitat (P<0.05). The NOS of wet habitat was higher than that of aquatic habitat (P<0.05). The CI was not significantly correlated with NOS across the habitat gradient (P>0.05), but the two were inverted parabolic in wet habitat (P<0.05). 3) Plant community species richness was parabolic with CI (P<0.05), and the remaining three diversity indices were linearly and positively correlated with NOS across the habitat gradient (P<0.05). In terms of individual habitats, the Simpson, Shannon-Weiner, and Pielou indices were linearly negatively correlated with CI in wet-mesic habitat (P<0.05), but these indices were not correlated with CI in aquatic, wet, and mesic habitats (P>0.05). None of these four diversity indices, i.e. species richness, Simpson index, Shannon-Weiner index, and Pielou index, correlated with NOS in any individual habitat (P>0.05). These results suggest that plant diversity in Zoige tends to increase from aquatic to mesic habitats, but the relationship between plant diversity and species competition and niche overlap is complex. The results contribute to the understanding of the mechanisms that shape plant diversity in the Zoige plateau.