Distribution patterns of Juglans cathayensis populations at different slope aspects in Tianshan valley in Xinjiang, China

Abstract

Eight 4000 m2 plots were set up at eight sites distributed on sunny and shady slopes of four valleys, and adjacent lattice method was used to survey Juglans cathayensis populations. At different scales, aggregation intensity index such as variance/mean ration and deviation index (Cx), negative binomial parameter (K), clumping index (I), mean crowding index (m*), patchiness index (PAI) and aggregation index (Ca) were used to analyze distribution patterns of populations. With the increase of surveying scales, the distribution patterns changed from cluster to random. Populations presented a clustered distribution when the scale was 25 m2. Aggregation intensity had great differences among different plots, and the maximum one located on west shady slope and the minimum one did on south shady slope. However, populations presented a random distribution when the scale was 50-400 m2. When scale was 25 m2, saplings, young and mature trees showed a clustered distribution. Aggregation intensity of mature trees was the maximum one and that of saplings was the minimum one. When the scale was 200-400 m2, saplings, young and mature trees showed random distribution. The pattern size of J. cathayensis populations was 25 m2 and pattern intensity was 2.49-9.38 m2. The pattern intensity of young trees was the largest and that of mature trees was the least in population components. In a word, when sampling scale was close to population patch size, a reliable conclusion usually could be obtained by using adaptive determination method and multi-index comprehensive decision.