海拔梯度对天山北坡天然草地鸭茅种群分布格局的影响

Effects of scale on the regional distribution patterns of Dactylis glomerata at different altitudes in the Northern Tianshan Mountains

采用邻接格子样方法,利用方差/均值比率、负二项参数(K)、丛生指标(I)、聚块性指标(m*/m)和Cassie指标(CA)等对天山北坡东段与西段不同海拔鸭茅(Dactylis glomerata)种群进行了空间分布类型、格局强度及格局规模分析。结果表明,分布类型上,鸭茅种群在东段与西段山地不同海拔地段呈聚集分布,均不服从随机分布;格局强度上,东段山地,鸭茅种群的分布格局强度为中度聚集,而在西段山地,除海拔2 000m处为中度聚集外,在海拔1 800和2 200m处鸭茅种群聚集强度均为强聚集;格局规模上,不同区域鸭茅种群的均方区组曲线均有1~2个明显的峰值,聚块最小面积0.2m^2,最大6.4m^2,不同海拔地段上,鸭茅种群在区组4、区组8、区组32和区组64上均有明显的峰值;鸭茅种群有随密度增大,平均拥挤度呈增大的趋势。

Spatial patterns of Dactylis glomerata were sampled using the contiguous grid quadrat method at various altitudes in the eastern and western sections of the Northern Tianshan Mountains and analysed using the variance to mean ratio,negative binomial parameter,index of clumping,index of aggregation,and Cassie＇s index.The results showed that the distribution was aggregated in both the eastern and western sections of the Northern Tianshan Mountains.The degree of aggregation of D.glomerata was moderate in the eastern section,but was moderate at an altitude of 2 000 mand high at 1 800 mand 2 200 min the western section.There were one or two peaks in the scale of the distribution pattern of D.glomeratain the different regions.The minimum area of aggregation was 0.4m^2 and the largest area was 5m^2.Peaks in aggregation appeared in block of 4,the block of 8,the block of 32,the block of 64 at different altitudes.Finally,mean crowding exhibited an increasing trend as density increased.