Characteristics Of Soil Seed Bank, Standing Vegetation And Soil Environment In Different Degraded Alpine Meadows On The Headwaters Of Yangtze And Yellow Rivers

The study on quantity characteristics of soil seed bank, standing vegetation, soil physical and chemical property, seed size and weight and so on were carried out in the 4-types of alpine meadows i.e. non-degraded meadow; minor degraded meadow; medium degraded meadow and heavily degraded meadow. The results as follows: 1. The difference of soil seed bank storage was not notable among different 4-types of meadows. The most was minor degraded meadow (15466.67±6072.02 seed/㎡) and the least was heavily degraded meadow (9422.22±1904.09seed/ ㎡). The amount of germinative seeds of soil seed bank in non-degraded meadow (2374.40±830.28 seed/㎡)was less than the other degraded meadows. Whereas no significant different (P﹥0.05) was shown among the minor degraed meadow (7712.00±1395.81seed/㎡), the medium degraded meadow (8614.40±3431.11seed/ ㎡) and heavily degraded meadow (6899.20±1514.03seed/㎡). 2. The soil samples from each type of alpine meadows were separated through 4 kinds of sieves with mesh size of 0.25 ㎜, 0.5 ㎜, 2.0 ㎜and 6.0 ㎜. The results showed that the diameter of the germinative seeds from non-degraded meadow mainly dropped to the size ranged from 0.5 ㎜to 2 ㎜while the diameters of the germinative seeds in the soil samples from the rest 3 types of degraded meadows concentrated on the range of 0.25 ㎜~0.5 ㎜. The further statistical data indicated that 94%~98% alpine meadows germinative seeds have a diameter range of 0.25 ㎜to 2㎜. Only 2%~6% germinative seeds were found in the soil samples of over 6㎜.There was no germinative seeds existed in soil samples of less than 0.25 ㎜. 3. The number and time situation of germinative seeds from each type of alpine meadows are both close to unimodal curve. The monocotyledon seeds began to germinate after ten days and the dicotyledon seeds began to germinate after five or seven days. The monocotyledon germinative seeds of medium and heavily degraded meadow were less than non-degraded and minor degraded meadow. Consequently the germination dynamic of the couple of samples both manifest the germination dynamic of dicotyledon seeds. 4. The plant community composition of different degraded meadows was changed. Species composition of standing vegetation took place change with the increasing of degradation. From non-degraded meadow to heavily degraded, the composing element of vegetation changed from good grasses to noxious weed gradually. The soil nutrients, soil moisture decreased and soil bulk density increased with gradually degrading. 5. The seed size and weight of 51 plant species in test area was researched. There were seeds weight of 40 species concentrated on the range of less 25.0mg, was 78.43% of all testing seeds. Moreover the most were perennial plant seeds (82.35%).