Competition and facilitation co-regulate the spatial patterns of boreal tree species in Kanas of Xinjiang, northwest China

Abstract Competition and facilitation are the primary mechanisms structuring communities and driving spatial distribution patterns of trees. However, we still know relatively little about the underlying effects of these two processes on natural forest ecosystems and this is particularly true in boreal forest ecosystems. Our lack of understanding regarding the factors regulating spatial patterns of boreal forest ecosystems is important given their role in carbon sequestration and timber products. Using data from a 12-ha boreal forest dynamic plot in the Kanas Nature Reserve of Northwest China, we assessed the population distribution and diameter at breast height (DBH) structure, as well as intra- and interspecific interactions, of the four most abundant tree species (Larix sibirica, Picea obovata, Pinus sibirica, and Betula pendula). Our results indicate that the spatial distribution patterns of these species were aggregated at small spatial scales because of dispersal limitation, and that the degree of aggregation decreased with increasing spatial scale. Aggregation was the highest for the less common species (i.e., B. pendula pendula). Saplings (1 cm ≤ DBH