| Recently, on the pressure of change of the climate acutely and over-disturbance by the human being, the normal development and succession of Seriphidium desert grassland vegetation became abnormality, and that degraded on large area. This study focuses on seriphidium desert at northern slop in Tianshan Mountain, analyze characteristics of grassland community and characteristics of distribution, the characteristic of fecundity and three major plant seed germination behavior. Describe soil seed bank characters and distribution pattern on horizontal direction, analyze the relationship of soil seed bank varibles, aboveground vegetation and soil nutrients. At the same time, analyze growth rule of seedlings, physiology and ecology characteristic, distribution pattern of Seriphidium(S. transiliense,S.brotaliense) population (include seedling and mature individual) to clarify action of Seriphidium in vegetation regeneration process. Finally, integrate data of vegetation, seed, soil seed bank and seedling to discuss patterns of regeneration of vegetation. The results showed that:(1) In short term fencing, plant density of Seriphidium desert grassland is impacted significantly, but it can not change significantly the structure of plant communities, at the same time, climate changes effect vegetation conditions acutely. Density of aboveground vegetation in inside fence higher than outside fence, and that vegetation density changes acutely because of climate changes during three years. Biomass of community changes significantly because of density of vegetation in different years. The variational characteristics of species, biodiversity index trend to complication. Distribution pattern of vegetation has heterogeneity significantly. Individual morphological characteristics of main plant species appears differentiation.(2) High seed yield of community provide important regenerated foundation for regeneration of vegetation. Fence and climate effect seed yield of community, seed yield in inside fence is higher than outside fence significantly, and fluctuating of seed yield is more acutely in different years because climate changes, and shows 2007>2009>2008. Fecundity characteristic of three plants (Seriphidium, Petrosimonia sibirica, Trigonella arcuata) are different, Seed yield and weight of single Seriphidium seedling are very sensitive to fence and climate changes in different years. Seed yield and weight of single Seriphidium seedling have difference significantly inside and outside fence in different years. Seed yield and weight of single Petrosimonia sibirica and Trigonella arcuata have difference significantly in different years. Germination rate of Petrosimonia sibirica are the highest among three plants species, followed by seriphidium, germination rate of Trigonella arcuata is the lowest because of dormancy. seriphidium and Petrosimonia sibirica seeds germination process depend on the seed weight.(3) Seedling emergence pattern from soil seed bank samples in different plots were unimodal curve. Large numbers of germinating seeds exist in soil seed bank and provide potential"regenerate bank"for vegetation regeneration. Seed number is higher in inside of fence than outside fence in soil seed bank, but composition of plant species is very simple and plant species number is 8-10.The similarity relationship of species composition between soil seed bank and vegetation decrease with increasing of degradation inside fence, then inverse trend in outside fence. Species of soil seed bank associate with soil nutrient, but this relationship of the same species is different in different plots. On horizontal direction, distribution pattern of every component of soil seed bank appear autocorrelation in small scale, but autocorrelation of variables is positive and negative alternately. Distribution of seed density is very complicated, and that has spatial heterogeneity significantly, appear mosaic distribution pattern.(4) Accumulation of aboveground biomass of Seriphidium seedling is very quickly during Apr-Jun, and then seedlings begin desquamate leaves, accumulation of aboveground biomass decreasing and length of root increasing, growth of aboveground and underground appears allometry type. Fpro,Sp and MDA concentration increase under drought condition,so Seriphidium seedling can accumulate physiological adjustment substance to resist drought condition, and make seedling come into regeneration of population. NPn of seedling decrease under drought condition and NPn increase with increasing of Photosynthetically available radiation, and seedling has light saturation point and light compensation point. Transpiration rate increasing with increasing of Photosynthetically available radiation. Drought condition reduce NPn of seedling and velocity of carboxylase/oxygenas, increasing CO2 compensation point of seedling.(5) When population density is very high(MD), seedlings are all clumped pattern of distribution in both inside and outside the fence , but the degree of aggregation is different inside and outside of the fence due to spatial heterogeneity of the micro-environmental conditions, relationships of seedling quantity and environment indicate that number of seedlings are positively correlated with environmental factors, litter, coverage of vegetation, branch of mature seriphidium individual and degree of degradation effect emergence and survival of seedling significantly. When population density is very low(SD and MD), relationship of seedling and maternal is very clear, distance between maternal and seedling is 50cm, and distribution pattern of seedling covert in spatio-temporal to increase individual fitness. Seriphidium mature population is usually characterized by clumped distribution in small-scale in three degree of degradation, when reach to threshold of the clumped distribution then shift to random distribution with increasing of scale. According to spatial association analysis of two sizes, results showed that two size of Seriphidium population is positive association in small-scale in three degradation gradient, but association is waning with increasing of scale.(6) Plant species number of vegetation, seeds, soil seed bank and seedling is 8-12, so composition of vegetation is simple. Lower density of vegetation can produce a large number seeds and come into soil seed bank, convert efficiency of soil seed bank to seedling is very low in MDI but that is increase in MDO. There are high density of vegetation , high seed yield and can produce a large number of seedling in SDI and SDO, convert efficiency of soil seed bank to seedling is very high. Lower density of vegetation can produce a large number of seeds in HDI and HDO, seed yield is equal to density of soil seed bank in MDI, but density of soil seed bank is higher than seed yield in HDO. Resource of regeneration of vegetation is seeds in three gradient of degradation. A large number of Seriphidium seedling come into recycling of regeneration in MDI and MDO, and that annual plant species is regeneration dominating in two others gradient of degradation.
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