Abstract: An investigation on the seed yield, seed dispersal pattern, seed density, and the numbers of seedlings and saplings was conducted at the sampling sites of Acacia glauca and Leucaena leucacephala plantations. The factors affecting the natural regeneration and tree adaptability of A. glauca and L.leucacephalawere analyzed, and their regeneration status was evaluated by gray relational analysis. The results showed that the seed yield of A. glauca with the same age was 566 grains per tree, while that of L.leucacephala was 1 199 grains per tree. The mean seed yield of individual tree, whether A. glauca or L. leucacephala, was higher in mixed forest than in pure forest, and that of naturally regenerated L. leucacephala forest was between those of A. glauca and L. leucacephala plantations. With the increasing distance to mother tree, A. glauca had a smaller decrement of seed density than L. leucacephala. The seed dispersal distance of A. glauca was 110 m, while that of L. leucacephala was 90 m. The gray relational coefficient of A. glauca plantation, L. leucacephala plantation, and naturally regenerated L. leucacephala forest was 0.7269, 0.6000 and 0.6000, respectively, indicating that A. glauca plantation had a better regeneration status.

Key words: Grassland fire behavior, Combustible, Influentia l factors, Predictive model, Songnen Plain