The Relationship Between Soil Seed Bank And Vegetation Recovery On Zokor Mound

Soil seed bank is an important component of natural vegetation succession and self-repair mechanism, largely represents evolutionary history, current status and future trend of vegetation, and plays an important role in the recovery and regeneration of aboveground vegetation. Plateau zokors are important members of alpine meadow ecosystem and have unique and important effects on soil seed bank traits and function in alpine meadow, and recovery of mound vegetation with the special way of subterranean existence for life and mounding by excavating. In order to probe into the relationship and mechanism between plateau zokor, soil seed bank and recovery of mound vegetation, the research was conducted in a typical distribution site of plateau zokors in Maqu county from 2004 to 2006, studying essential characteristics and correlations among mound distribution pattern, plant community, seed rain, soil seed bank and mound seed bank. The main results are as follows:1.Plateau zokor mounds can be separated into three age categories: new or less than 1 year old, intermediate or 2 years old and old or 3 years old, according to their formation time. During the study, the quantitative relationship among three kinds of mounds has been maintained 1:1:1, indicating that the population density is relatively stable. Thus, we could make prediction on ebb and flow trend of population quantity with the proportional relationship among three kinds of mounds. Since the number of mounds formed before August is easily to determine the nature and has larger practical significance, consequently, it is more suitable to be used as relative density index of plateau zokor.2.In typical plateau zokor habitats of sub-alpine meadow, the average density of soil seed bank is 4836 seeds/m~2 , species number is 38, distributed among 19 families, and perennial plants are absolutely predominant, accounting for 85% of the total species number.3.Species number of vegetation is 46, and annuals approximately account for 10%, significantly higher than that in sites of no plateau zokor. Species number of vegetation is significantly higher than that in soil seed bank (38), and they are distributed more extensively among families, similarity indices between the two are around 68%.4.Seed bank density of mound, species number and seed viability all increase markedly with the increased mound age. There are extremely significant differences between new mounds and other kinds of mounds in seed bank density and species number (P < 0.01), while the differences between 2 years old and 3 years old mounds are significant (P < 0.05); seed viability of new mound seed bank is significantly lower than that of 2 and 3 years old mounds (P < 0.05), and seed viability of 3 years old mounds is higher than that of 2 years old mounds, but not statistically significant (P > 0.05). 5.Components of seed rain are different than that of mound seed bank, but species components of seed rain and vegetation are relatively similar. Species number in mound seed bank occupies 82.05% of that in seed rain, and 69.57% of that in vegetation. Obviously, seed rain is material base of recruitment and renewal of mound seed bank, important seed sources of mound vegetation recovery, and one of the important mechanisms to maintain plant diversity.6.Mound density is an important factor affecting vegetation traits. Species richness, aboveground biomass and Shannon-Winner index all peak in intermediate density plots across mound density gradients, thus, certain number of plateau zokor in alpine meadow contributes to optimization of community structure, and promotes markedly the enhancement of species diversity and aboveground biomass.7.Similarities of species components between mound seed bank and mound vegetation increase with the time of mound formation. Similarity indices between species components of new, 1 year old ,2 years old and 3 years old mound send bank and corresponding mound vegetation are 60.07%,65.82%,70.41% and 76.57% respectively; while vegetation cover, species components and other property indices also showed increasing convergence to that of background vegetation. Accordingly, recovery cycle of mound vegetation should be between 4 to 5 years.