[Effects of microtopography on the pattern and association of dominant population.]
Different spatial distribution patterns and correlations could reflect the adaptation strategies of plant populations to different habitats. Geranium wilfordii and Gueldenstaedtia verna are the major species in the subalpine meadow. Within a field experiment, the Ripley K function was used to analyze the relationship of spatial distribution pattern and interspecific association between G. wilfordii and G. verna in different slope aspects. The results showed that soil water content and nutrient content gradually increased, whereas soil temperature and light intensity gradually decreased along the gradient from south to north slope. The distribution of G. verna and G. wilfordii showed significant differences in three slope aspects (north, west and south slopes). G. verna showed an increa-sing trend, while G. wilfordii showed a decreasing trend from north to south slope. On the north slope, G. verna populations showed aggregation distribution at 0-1.8 m scale, while the aggregation intensity weakened and tended to be a random distribution at 1.8-5.0 m scale. G. wilfordii populations showed aggregation distribution at 0-5.0 m scale. On the west slope, G. verna population showed aggregation distribution at the 0-1.2 m scale, and tended to be a random distribution at the 1.2-5.0 m scale. G. wilfordii population showed aggregation distribution at the 0-2.2 m scale, and tended to be a random distribution at the 2.2-5.0 m scale. On the south slope, G. verna and G. wilfordii population showed random distribution at the 0-5.0 m scale. Both species showed positive correlation at the 0-1.0 m scale but not at the 1.0-5.0 m scale on the north slope. G. verna and G. wilfordii were negatively associated at the 0-2.1 m scale but unrelated at the 2.1-5.0 m scale on the west slope. On the south slope, both species showed no correlation at the 0-5.0 m scale.