The Differentiation Of Forest Soil Seed Bank Among Micro-landforms In Tiantong Mountain

The soil seed bank is one of the main elements of forestry ecosystem, which plays an important role in vegetative restoration and regeneration. Landforms provide the main heterogeneity of spatial structures, and could influence the vegetation pattern directly or indirectly. Above ground vegetation provided the main seeds which reserved in soil seed bank. Accordingly, the vegetation influenced by landforms could affect the soil seed bank. Compared to many researches on vegetation patterns in large-scale, less works had been reported in small/micro-scale. Little of the roles and functions of soil seed bank to above ground vegetation differentiation in small/micro-scale had been noticed.In this research, eight micro-landform units were selected in Tiantong national forest park for analyzing the spatial and temporal patterns of forest soil seed bank. We collected 1960 soil samples in September 2008, December 2008, March 2009 and June 2009 (480 samples each time). Seeds were picked out from the soil samples and its vitality was checked. The results are summarized as follows:First,68 species were picked out from the soil samples, of which,65 species belonging to 33 families and 54 genera were identified. Evergreen broad-leaved sub-tree seeds and deciduous broad-leaved tree seeds were the main components of the total soil seed bank, with the former accounted for 35.5 percentages and the latter 28.3 percentages; evergreen broad-leaved tree seeds accounted for 8.5 percentages; deciduous broad-leaved shrub seeds accounted for 5.8 percentages; deciduous broad-leaved tree seeds accounted for 5.6 percentages, and the last 5 types of life form seeds accounted for less than 5.0 percentages respectively. The broad-leaved woody species occupied 82.4 percentages of the total species in soil seed bank, and the herbaceous species accounted 13.2 percentages.Second, differentiation occurred between micro-landforms in respect of life forms of specie in soil seed bank. The results of cluster analyses indicated that the eight micro-landforms could be classified in to two sections, namely upper hillside area (including 3rd crest slope,2nd crest slope,high-upper sideslope,middle-upper sideslope and low-upper sideslope) and lower hillside area (including lower sideslope,foot slope and flood terrace). Evergreen broad-leaved wood species were the main component of the life forms in upper hillside area; deciduous broad-leaved wood species were the main component of the life forms in lower hillside area.Third, spatial pattern of the soil seed bank showed a dumbbell-shaped style, i.e., the reserves on crest slope and lower hillside area (including lower sideslope, foot slope and flood terrace) were both higher than that on upper sideslope. The reserves of the four vertical soil layers were of different sizes, with the largest at 0-2 cm soil layer, followed by that at 2-5 cm soil layer and that at 5-10 cm soil layer, and that at litter layer was the smallest. Species were distributed optionally over four vertical soil layers.Fourth, soil seed bank showed significantly seasonal dynamics, the largest reserve appeared in December 2008, followed by that in March 2009, September 2008 and June 2009. Variance analysis and multiple comparisons by One-Way ANOVA indicated that differences in soil seed bank reserves of June and that of March were significant at 0.05 level, and the differences between June and December were significant at 0.01 level. There existed seasonal dynamics in species composition of soil seed bank.Fifth, double-side bet strategy was detected in soil seed bank which contributed to above vegetation regeneration:on the one hand, the seeds in litter layer,0-2 cm soil layer and 2-5 cm soil layer germinated quickly for building seedlings bank which could provide substance for vegetative restoration and regeneration; on the other hand, the 5-10 cm soil layer stored stable soil seed bank reserve for avoiding risks, and ensured the vegetative restoration and regeneration.Last, compared to other forest soil seed bank, the reserve of Tiantong Mountain was of lower-middle level, and the species similarity between the soil seed bank and the above ground vegetation showed lower community similarity level (Sc=0.42). These situations wakened the restoration and regeneration potency of the vegetation.