| The special pattern of the constructive species is the important features of the community. Plant spatial pattern of the species is determined by their biological characteristics and environmental conditions. It has been the focus in the plant ecology. Quercus aquifolioides scrubs are typical types of vegetation in western Sichuan, China. It is critical to analyze the spatial patterns for its important function on depicting the ecological processes of Quercus populations. Therefore, the spatial patterns of this species were investigated and analyzed, in this study for three main aims:1) to describe the spatial patterns and individual association changes along with the elevation gradients; 2) to figure out the relationships between the spatial scales and the spatial patterns; 3) to analyze the effect of plants sizes on the spatial patterns and the individual association. The distribution range of Quercus in Ba Lang Mountain, Sichuan was chosen as the study area. Four elevation gradients were set up in the study area, which included the elevation of 2400m, the elevation of 2800m, the elevation of 3200m, and the elevation of 3600m. Four plots with the size of 50m×50m were established in each elevation gradients, where Quercus plants were recorded and mapped. In order to identify the differences and associations between the Quercus populations, the plants were divided into four plant size level by the product of coronary diameter and height. The types included plant size 1, plant size 2, plant size 3, and plant size 4. The point-pattern analysis is effective and realizable for the measurement of the spatial patterns. Accordingly, point-pattern analysis was used to evaluate the spatial distribution patterns and individual association of Quercus populations along altitudes gradients, spatial scale and plant size. The results showed that:1) Judging from the importance value of the species. Quercus is the single priority populations, the others are mainly Cotoneaster horizontalis, Salix eriostachya and Berberis diaphana. With the elevation increasing, the amount of Quercus populations was changed, with the most amount at the elevation of 2800m. In these four elevation gradients, the amount of the four plant sizes varied in the following order: plant size 2> plant size 3> plant size 4> plant size 1.The amounts of Cotoneaster horizontalis and Berberis diaphan were also changed, with the most amount at the elevation of 3200m,and to the Salix eriostachya, the most amount at the elevation of 3600m.2) The soil bulk density goes up with the increase of soil depth, in contrast, soil water holding and porosity reduce with the increase of that. With the increase of elevation, soil bulk density in every layer tends to increase first, then decrease, and then increase again. To the soil water capacity and porosity, it tend to increase first,then decrease.3) The spatial patterns and their individual associations closely related to the spatial scale, the plant size and the altitude gradients. On a smaller scale, Quercus populations were in clustered distribution, with strong spatial association among individuals; with the spatial scale increasing, the spatial distribution pattern of Quercus populations gradually became random, and individual association was weakened to no association.4) The spatial association between Quercus and other main species shows the competition between Quercus and Salix eriostachya, and the coordinate relationship between Quercus and Cotoneaster horizontalis.5)The differences of plant size among individuals was another important factor that affected the spatial associations, the larger differences of plant size among individuals, the stronger associations between individuals were existed, and vice versa. For example, the differences between plant size 1 and plant size 4 were the largest, so the special association between them was the strongest, which basically showed a negative association.
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