Structuring mechanism of tree species diversity pattern in a near-mature forest in Jiaohe, Jilin Province

The effect of plant species on the community diversity pattern has long been a key issue in ecology. A 21.12 hm2 near-mature forest plot was established in Jiaohe of Jilin Province. Totally, 32 405 woody individuals with diameter at breast height (DBH) 1 cm belonging to 50 woody species were recorded. Individual species-area relationship (ISAR) was used to quantify the effects of 30 woody species on local community diversity pattern. Complete spatial randomness simulation was adopted to calculate the significance of facilitation or suppression. The results show that: 1) ISAR value is generally higher than mISAR value for the same tree species in the same sampling area, because ISAR model ignores asymmetry of competition. The mISAR curves for different tree species are more dispersed, and have higher differnentiation degree and obvious scale dependence. 2) At 0 - 50 m scales, Acer barbinerve, Cerasus maximowiczii, Euonymus macropterus, Padus racemosa, Ulmus macrocarpa, Acer ukurunduense, Corylus mandshurica and Acer tegmentosum are diversity accumulators while Sorbus alnifolia is a neutral species. Pinus koraiensis, Acer mono and Juglans mandshurica are diversity repellers at most spatial scales. Most of the other tree species act as diversity accumulators at small scales. 3) Diversity accumulators dominate the community diversity pattern at the small and medium scales. Diversity accumulators and neutrals jointly affect the structuring of the community diversity pattern at large scales, and the influence of stochastic process is relatively stronger. Therefore, deterministic process represented by accumulators and repellers and stochastic process represented by neutral species collectively determine the structuring processes of community diversity pattern, and the effects of two processes differ at different spatial scales.