Abstract: By the methods of collecting seed rain with traps, sieving soil seed bank, laboratory seed germination experiment, and field  investigation, this paper studied the compositions and spatiotemporal distribution features of soil seed bank and seed rain in six Abies fabri forests with different ages and at different altitudes in Gongga Mountain of Southwest China. The size of soil seed bank decreased with increasing soil depth, and the seeds mainly concentrated in litter layer. At the same altitudes, the sizes of soil seed bank and seed rain decreased after an initial increase with increasing forest age, and the biggest values were found in mature forests. Moreover, the percentage and the overall quality of intact seeds were the highest in mature forests. At different altitudes, the seed density of soil seed bank and seed rain in the mature forests with similar ages were apparently lower at higher and lower altitudes than at intermediate altitudes, which could be related to the differences of water and heat conditions. It was suggested that mature A. fabri forests had the best productive phase, their seed quality was good, and their micro-habitat condition was most suitable for the seed conversation after dispersal, possibly because of the unique biological features of A. fabri and its micro-habitat condition.

Key words: dryland wheat, mulching in fallow period, soil moisture, nitrogen absorption, nitrogen translocation.