Objective To understand the present situation of the soil seed bank of a Pinus densata forest for the purpose of protecting and managing the P. densata forest.

Method In this study, the P. densata forests in different locations of Gongbu Nature Reserve were used as research objects. The spatial distribution pattern of P. densata soil seed bank was systematically studied by combining field survey sampling and laboratory test analysis.

Result (1) In term of seed density of P. densata soil seed bank, no significant defference was found in different periods in the four directions of east, south, west and north (P > 0.05). However, with the sampling time, the seed density of P. densata soil seed bank in Dongjiu sample plot showed a decreasing trend, while with the sampling time, the seed density of P. densata soil seed bank Nyingchi sample plot and the Birity Mountain sample plot increased at initial and then decreased. (2) With the increase of the horizontal distance from the parent tree, the seed density gradually becomed smaller, i.e., 1 m > 3 m > 5 m, showing a distinct distribution trend of the near mother tree. The seed bank density of P. densata soil in different periods showed the Birity Mountain > the Nyingchi > the Dongjiu. (3) With the increase of soil depth, the amount of seed gradually decreased, and amng the total amount of seeds, above 89% was distributed in the litter layer and 0-2 cm soil layer. (4) In general, the seed density of the soil seed bank of P. densata forests increased with the elevation. However, as far as the Dongjiu and the Nyingchi sample plots were concerned, it followed a pattern of half-mountain < top and foot of the mountain, showing a "V" shape. (5) Most of the infesting seeds was found in the soil seed bank, accounting for more than 35% of the total seed. With the sampling time last, the amount of mouldy seeds increased gradually, the proportion of intact seeds decreased, and the amount of viable seeds was very few, which accounted for only 1.43% of the total seed, and 73.38% of the viable seeds ware stored in the litter.

Conclusion There is no significant difference in the distribution of P. densata soil seed bank in different orientations at different times, but there are obvious distributions at different distances from the parent tree and different soil depths, which are mainly formed by the joint influence of the characteristics of the seeds and the external wind. With the sampling time changes, the amount of mouldy seeds increases, relating mainly to the high humidity and rainy climate in Gongbu Nature Reserve.