Storage and distribution of soil seed banks in degraded mountainous area of dry-hot valley in Nanjian, Southwest China.

Through the methods of transect sampling and greenhouse germination trial, the authors examined the storage, distribution pattern,composition and dominant species of soil seed banks of the rehabilitated communities and the local secondary vegetation on degraded mountainous area of dry-hot valley in Nanjian, Southwest China's Yunnan Province. The seed densities in the top soil of 10 cm varied between 2 060 and 21 300 grain per m~ 2,and the number of species identified varied between 22 and 32 among 5 types of rehabilitated communities and the local secondary vegetation. The storage and the species numbers of soil seed banks of the rehabilitated communities greatly increased in comparison with the local secondary vegetation. In the soil samples of 10 cm, the result of seed banks was in the order of upper layer (0--2 cm) middle layer (2--5 cm) lower layer (5--10 cm), and statistical test of difference of seeds germinating from different soil layers in different community types was significant. In terms of the species composition and life form, herb species dominated the soil seed bank with a higher density and accounted for a high proportion of the soil seed bank. A few species of Asteraceae such as Eupatorium adenophorum, Ageratum conyzoides, Carpesium cernum and Leontopodum dedekensii were dominant in the soil seed bank. But Heteropogon contortus, one of dominant species of the herbaceous layer on the ground, seldom appeared in the soil seed bank.