Spatial Distribution Pattern of Quercus mongolica Population in Wudalianchi Volcanoes, China

Studying population spatial patterns is an effective way to deeply understand the functions and processes of population ecology. Assessing the spatial distribution patterns of dominant populations in forest communities provides reference data to elucidate the ecological characteristics of the population and the trend of community succession. The subject of our research was a Quercus mongolica population on the southern slopes of four old volcanoes in Wudalianchi. The Q. mongolica population was divided into different age classes and non-age classes. To assess the spatial distribution characteristics of the different classes on different spatial scales, the Q. mongolica data for the four volcanoes were analyzed by a multi-scale and multi-index comprehensive judgment method. The main findings are as follows. (1) The spatial distribution of Q. mongolica classes varied with spatial scale at the four volcanoes. The age-disaggregated classes were mainly clustered at the 200-m² and 400-m² scales, but the intensity of clustering was significantly different. The cluster distribution of age-class Ⅴ was significantly different at the 25-m² and 50-m² scales, whereas that of age-class Ⅶ was significantly different at scales of 200-m² and 400-m². (2) The spatial distribution pattern of Q. mongolica classes exhibited obvious scale effects in the four volcanoes. The six discriminant indexes showed different trends with increasing scale. The power increase was greatest for the age-disaggregated classes (46%), and the maximum power increase was 50% for age-class Ⅶ. (3) The size of sub-populations of Q. mongolica differed among the four volcanoes. In the age-disaggregated classes, only the mean square value of East Jiaodebu Volcano was extremely significant at the 200-m² scale, and the population size was 200 m². In the age-class V, only the mean square value of South Gelaqiu Volcano was significant at the scale of 400 m², and the population size was 400 m². For both age-class Ⅵ and age-class Ⅶ, only the mean square value of East Jiaodebu Volcano was significant at the 400-m² scale, and the pattern scale was 400 m². In this study, factors such as the spatial scale, age class structure, and stage of community succession, as well as the interactions between and cumulative effects of these factors, may be the main reasons for the significant differences in the spatial patterns within the studied Q. mongolica population. The population pattern scale should be further studied.