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

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 m and high at 1 800 m and 2 200 m in the western section. There were one or two peaks in the scale of the distribution pattern of D. glomerata in the different regions. The minimum area of aggregation was 0.4 m2 and the largest area was 5 m2. 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.