Studies On Soil Seed Bank And Regeneration Of Degraded Alpine Grass-land In The Headwaters Of Yangtze And Yellow Rivers On Tibetan Plateau

Recently, on the pressure of change of the Global climate acutely and over-disturbance by the human being, the normal development and succession of alpine cold grassland vegetation became abnormality, and that the alpine grassland degraded on large area and with many patterns in the headwaters of Yangtze and Yellow rivers (HAYYR) on Tibetan Plateau. There is a special production came from the heavy degraded alpine grassland in the world, which is'Black soil land'vegetation. The'black-soil-land'resulting from extreme degraded alpine meadow is reported in recent three decades. After the sod layer of meadow ranging from 10 cm to 15 cm deep is totally removed by intensive grazing and activities of rodents, the uncovered sub-soil appears, this land is called as the'black-soil-land'. Up to now, several researchers defined black soil land grassland degradation, described the extent and mechanism of degradation and reviewed the strategies for restoring and reconstructing the degraded alpine grasslands. However, there are several questions puzzled in the process of alpine grassland degraded (from normal alpine meadow to'black soil land'). (1) What change of soil seed bank (size and component), (2) whether change of soil seed bank drive grassland vegetation degraded or influenced by vegetation, and what role play by soil bank in alpine grassland degraded and restoration? (3) What and how change every stage of vegetation regeneration in the process? (4) What significance of vegetation propagative bank to degraded grassland restoration or reestablishment especially'black soil land', (5) how can we understand those ecological processes under different temporal and spatial scales in alpine grassland? In order to explain those question, four different degraded degree of alpine meadows(no-degraded or normal meadow-ND, light degraded meadow-LD, medium degraded meadow-MD, heavy degraded meadow i.e.'black soil land'-HD) were sampled, and soil seed bank, seed rain, seedling bank on aboveground and standing vegetation and their relationship were investigated in field and laboratory.The result showed that, the size of most seeds of soil seed bank in degraded alpine meadows are 0.25 mm-2 mm. Mesh diameter between 0.25 mm and 2 mm was applied in this experiment. Seedling emergence patterns from four seed banks were unimodal curve, and conic curve were fitted finely significantly, especially, the unimodal curve fit the normal meadow seedling emergence pattern were significantly greatly (p<0.01). There were no evidently change rule among different degree degraded of alpine meadows about the pattern of seedlings emergence from soil seed banks, and which indicated that...