THE STUDY ON SEED RAIN CHANGE OF STIPA GRANDIS COMMUNITY IN THE SONGNEN PLAIN OF CHINA
松嫩平原大针茅群落种子雨动态的研究

In light of the field-investigation at the fixed position from 1982-1988, a quantitutive analysis was done on the change of seed rain,and the relationships between the seed rain and water-heat climaticfactors in Spipa grandis community was discussed in this paper.There we-re 46 plant species altogether and 9 of which were constant species inthe seed rain of the community. The density of S. grandis which is domi-nant species was only about 0.3-1.3% in the total density of the seedrain every year. The seed rain density of dicotyledon group was generallyabout 1.5-13.5 times higher than that of the monocotyledon group, andthe perennial group were 0.2-7.4 times higher before 1985, but 0.4-1.0times lower after 1986 than the annual group in the community. The rati-os of hemicryptophytes were usually the highest in life form spectrum ofthe seedrain plants every year. There was positive correlation of differentvalue between the seedrain densities of both some plant groups and con-stant populations and the sunshine hours,the accumulated temperature,therainfall in the earlier-middle growing season,and the rainfall in differentperiods preceding growing season respectively.