【摘要】 狼毒 (Stellera chamaejasme)为瑞香科多年生草本植物 ,是主要的草地有毒植物种类之一。采用邻接格子样方法和分布指数 (DI)以及平均拥挤度 (m* )指标 ,研究了内蒙古西辽河平原北部典型草原区内的狼毒 (Stellera chamaejasme)种子种群分布格局强度、类型与规模 ;根据顺序远离母株的取样调查 ,定量地分析了狼毒种子在 8个方向上的散布格局。结果表明 ,狼毒种子在落种期之前为随机分布 ,而在落种期结束后为聚集分布 ,种子种群斑块大小平均为 0 .0 8m2 。狼毒种子在 8个方向上的散布表现为不同的散布格局模式。在不同方向随着累积面积增加狼毒种子散布数量变化符合 L ogistic曲线增长。各方向种子散布数量与顺风风向频率显著正相关。狼毒种群具有“近母株散布”的种子散布机制 ,基本散布半径为 0～ 5 0 cm。狼毒种群通过种子散布扩展其分布空间的能力是很有限的更多还原

【Abstract】 Stellera chamaejasme is a perennial herbaceous plant of Thymelaceae. It is poisonous to herbivores and widely distributes on grasslands in Northern and Northwestern China. S. chamaejasme population increases rapidly on degraded grasslands, which can negatively affect the health of livestock. The objective of this study was to determine the distribution and dispersal patterns of S. chamaejasme seed population, to determine its spatial dynamics and to provide baseline for its control.The research site was located at a typical steppe in Alukerqin County, Chifeng Prefecture, Inner Mongolia (120°25′E, 43°43′N). Vegetation is S. chamaejasme + Enneapogon borealis associationand with S. chamaejasme being the dominant species. The sampling of soil seed bank was conducted both before and after the onset of seed disprsal of S. chamaejasme (early May and late June, respectively) with the Contiguous Grid Quadrat (CGQ) design. Seeds were separated from soil samples using a sieve with apertures of 0.45 mm and then counted. Seed distribution pattern of S. chamaejasme was measured by the two parameters, dispersion index (DI) and mean crowding index (m~*), and tested for Poisson and Negative Binomial Distribution using χ~2 test. Data were analyzed with the Greig-Smith’s method——Paired Quadrat Variance (PQV). Eight directions (E, S, W, N, NE, SE, SW and NW) were selected from the basal tiller of S. chamaejasme for seed dispersion. Soil samples were collected from the basal tiller along each direction at 5 cm intervals. Correlation analysis was conducted between total seed density at different sampling directions and tail wind frequency, and between seed density and mean wind speed.Results show that before the onset of seed dispersal, the distribution of seed population of S. chamaejasme was random, but the distribution was aggregated distribution after seeds had been dispersed. The dispersion indices were 1.16 and 1.70, respectively, for seeds before and after dispersal, and mean patch size for seed population was 0.08 m~2. Patterns of seed dispersion varied according to directions. The increase in accumulative seed number with increasing sampling area followed the Logistic model. The dispersed seed quantity was significantly positively correlated with the tail wind frequency, but was not significantly correlated with mean wind speed. We conclude that S. chamaejasme seed population has a dispersion mechanism as “short-distance to parent tiller” (the dispersion radius was 0~50 cm in this experiment). The diffusion capacity of S. chamaejasme seed populations is limited by its physical structures (i.e., cannot be dispersed by animal and wind).更多还原