基于零模型的宁夏荒漠草原优势种群点格局分析

植物种群空间分布格局是多种生态过程综合作用的结果。明确植物优势种群个体的空间分布格局与形成机制有助于认识种群生态适应对策与群落多样性维持机制。以宁夏荒漠草原优势种群蒙古冰草、短花针茅、牛枝子和牛心朴子为研究对象,采用完全空间随机零模型分析其种群空间分布格局特征,并通过异质泊松零模型与泊松聚块零模型探讨生境异质性、扩散限制等因子在其空间分布格局形成过程中的作用。结果显示:(1)完全空间随机零模型下,4个物种在4 m尺度范围内表现为聚集分布,随尺度增大,逐渐过渡到随机分布和均匀分布。(2)在排除生境异质性的异质泊松零模型下,蒙古冰草种群在整个研究尺度上表现为随机分布;牛枝子、短花针茅和牛心朴子种群仅分别在0—0.2、0.1—0.4 m与0—0.2 m尺度范围内发生偏离,表现为均匀分布与聚集分布,其他尺度均为随机分布。(3)在排除扩散限制的泊松聚块零模型下,所研究种群均表现为随机分布。综上,荒漠草原优势种群在小尺度范围内主要表现为聚集分布;生境异质性与扩散限制均是驱动其空间分布格局形成的重要因子,相对而言,小尺度空间范围内扩散限制的作用更为显著。

Point pattern analysis of dominant populations based on null models in desert steppe in Ningxia

The spatial distribution patterns of plant populations are the results of the combined effects of various ecological processes. Exploration of the spatial patterns and their driving mechanisms of plant populations is helpful in elucidating the ecological adaptation strategy of a population and maintenance mechanism of the community. To understand the spatial patterns and their formation mechanisms of the dominant species in desert steppes in Ningxia, four 10 m×10 m sample plots which dominated by Agropyron mongolicum, Stipa breviflora, Lespedeza potaninii, Cynanchum komarovii were established, respectively. The spatial coordinates of the dominant species were measured by using adjacent lattice method. Their spatial distribution patterns were analyzed based on complete spatial randomness null models, and their driving factors were explored based on heterogeneous poisson process null mode and poisson cluster process null model. The results showed that (1) when using complete spatial randomness null model, all populations presented the aggregated distribution at < 4 m scales and random and uniform distributions at larger scales. (2) By using heterogeneous poisson process null model, the four dominant species mainly showed random distributions, but the S. breviflora, L. potaninii and C. komarovii departed from heterogeneous poisson process at much smaller scales. (3) The measured values of four species were accordance with poisson cluster process null model at the 0-5 m scale, appearing as random distribution. In conclusion, the four dominant populations mainly appeared as aggregated distribution. The spatial patterns of the dominant species were driven together by habitat heterogeneity and dispersal limitation in desert steppe in Ningxia. Relatively, the dispersal limitation played more significant roles at the small spatial scale.