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Plantations provide wood for the human, to slow the increase in atmospheric CO2 concentration, increase the terrestrial forest coverage and slow the human at the same time depends on the natural forest, also appeared in a series of ecological problems, such as the decline in biodiversity, land degradation, reduced productivity At its core is a biodiversity issues. The soil seed bank is present in a certain volume of soil dynamic dormant and not dormant seeds. Restore vegetation, natural regeneration and recovery, biodiversity maintenance plays an important role. Previous studies have mostly concentrated on the natural vegetation or arable soil seed bank, and less on the plantation soil seed bank study; and with the succession of plantation development, soil seed bank will also change accordingly, but few studies have forest age factors into account. In this study, as the research object, 1-10 years old Eucalyptus grandis plantation soil seed bank composition, dominant groups increased with stand age between soil seed bank diversity dynamic ecological processes and the seed bank and understory vegetation correlation. A more comprehensive system to understand the the returning farmland process soil seed bank characteristics and its updated the significance of the aboveground vegetation, provide a theoretical basis for plantation biodiversity protection and management to reduce the negative effects and to continue as a going concern. The results show that: 1) 1-10 years old Eucalyptus grandis plantation soil seed bank in the Chinese Communists were 58 kinds of plants, belonging to 38 families and 48 genera, water smartweed, crabgrass, seeking Spartina is the dominant species; common species of Acanthaceae before the rat yeast rice grass, Qixing lotus, teff, fish-eye grass, ground ear grass, Phyllanthus, chickweed, three grasses, sedges, wrinkled leaves Setaria, oxalis, stone raw chickweed, violet, car grass, the bare flower water bamboo leaves, water centipede the autumnal equinox grass, Indian strawberry, glutinous rice, paspalum. The rest is a rare species. 2) 1-10 years Eucalyptus grandis plantation soil seed bank of species in forest age lt; 5 year fluctuations, a minimum five years, and then increased with stand age increased to 10 years, seed The library first year, 1.9 times the number of species. Stand age of Eucalyptus grandis plantation soil seed bank species composition of herbaceous species, the density of the soil seed bank is changing with increasing stand age, afforestation early years of soil seed density (3090 ind m-2), Eucalyptus grandis forest soil seed libraries density 1 Dao 6 years students reduce (p-lt; 0.01) thereafter with stand age growth and increase the density of the sixth year of the soil seed of the lowest (1222 ind m-2), 10 years, soil seed bank density to 2098 ind m-2. Herb seed density and soil seed bank overall density changes with stand age; shrub species density in the early years of a minimum of afforestation (5 ind m-2) ,1-3 years increased (p <0.05), 3-5-year reduce, and then significantly increased with the increase of forest age, 10 shrub species seed density of up to 202 ind m-2, 3) 1-10 years of giant eucalyptus plantation soil seed bank has a table cohesion. The soil seed heavily concentrated in the 0-5cm, followed by the litter layer ,5-10cm at least. Eucalyptus grandis plantation of 1-10 years, the average number of seeds in the litterfall accounted for 20-21% of the total number of seeds; average number of seeds in the surface soil (0-10cm) accounted for 79-80% of the total number of seeds visible litter layer will be stored for a certain amount of the seed, but far topsoil saved more. Eucalyptus grandis plantation in 1-10 years, the topsoil average seed density ,0-5cm soil layer accounted for 76-77% of the total seed accounted for 2-3% lower (5-10cm), each stand age of Eucalyptus grandis the density of the soil seed bank decreased with soil depth deepened (p lt; 0.01). 4) 1-10 Eucalyptus grandis plantation soil seed bank shrub species, Shannon-wiener index elevated 1-3 years (p lt; 0.05) ,3-6 years to reduce (p lt; 0.05), then increased with stand age And increased (p <0.05). Pielou evenness index elevated 1-3 years 3-6 years decreased then increased with stand age increased, but the overall trend was not significant. Simpson dominance index was elevated 1-2 years 2-3 years to reduce elevated, 3-6 years, and then increased with stand age, the change was not significant. Herbaceous species diversity index increased with stand age changing Shannon-wiener index 1-5 lower (p lt; 0.05), then increased with stand age increased (p <0.05). The Pielou index with stand age increased without a significant change with Lin 1-5 years, Simpson index increased, then decreased with stand age increased, but the change was not significant. From the community level, the soil seed bank of the Shannon-wiener index 1-5 fluctuations reduced (p lt; 0.01), then increased with stand age increased (p lt; 0.01) Simpson dominance index increased (1-5 years p <0.05), and then decreased with stand age the Pielou index 1-5 years decreases then increases with stand age, but was not significant (p <0.05); 5) an age sequence of Eucalyptus grandis plantation soil seed bank diversity index and farming soil seed bank diversity index for multiple comparisons found that, in addition to outside afforestation 1 year was not significant, the early years (2-4 years) significant, high forest age stage 9,10 annual average was not significant, and the rest of the year is significant. 6) farmland to create a Eucalyptus grandis plantation 10 years, the number of species of understory vegetation and plant richness decreased in 1-5 years, and then came with stand age increases, two 10-year-old woodland indicators increased for the first year 5.09 and 5.83 times. 10 plots appear 78 kinds of plants belonging to 44 families, 65 genera, mainly shrubs and herbs. Herbal advantage in the number of species and individuals. The afforestation initial species richness and diversity of the herbaceous layer above the shrub layer, the number of species of the herbaceous layer in forest age gradually lower than the number of shrub species, forest age irrigation, grass species richness flat. Simpson index (D) and Shannon-weiner index (H) was similar rise in 1-3 years, followed by two years of decline and then rise, low forest age, D and H values ??higher than the shrub species of herbaceous species, shrubs below the high forest age layer; Pielou index (Jsw), changes in volatility, high forest age Jsw value higher than the low forest age 1-5 years herb layer below the shrub species, shrub layer is higher than the high forest age. 7) with Jaccard similarity coefficients C1 to the similarity of the soil seed bank and aboveground vegetation that soil seed bank and understory vegetation similarity lower.
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