The Dynamics Of Soil Seed Bank And Seedling In Hunshandake Sandy Land

In the Hunshandake sandy land in Zhenglan Banner of Xilinguole, Inner Mongolia, four types of sand dunes such as fixed dune, semi-fixed dune, moving dune and flat dune were choosen to set up research sites. Using the methods of sampling and germinating, soil seed bank, seedling and their relationship between aboveground vegetation were studied from April 2004 to September 2007, the results were as follows:1. The major species of soil seed bank were annual-biennial herbs. Soil seed bank density in fixed dune was 6273.5±273.37grain / m~2, followed by semi-fixed dunes was 2754.7±147.05grain / m~2, 1520.4±115.47grain / m~2 in flat dunes and 339.5±11.25 grain/m~2 in moving dunes.2. The density of soil seed bank was highest before growing season; lowest at the end of growing season. The seasonal difference of seed banks was significant in fixed dunes, semi-fixed dunes and plat dunes (p <0.05); but there was no significant difference in moving dunes (p > 0.05). There was no significant difference on each sand dune over four consecutive years.3. The horizontal distribution of the soil seed bank had the characteristics of uneven state. The density of soil seed bank decreased sharply in fixed dunes and flat dunes with the deepening of layer thickness, there was significant difference between layers (p <0.01); the density of soil seed bank decreased with soil depth increase in semi-fixed dunes, but there were no difference between 0 ~ 10 cm layer and 10~20 cm layer(p>0.05); There was no significant difference between layers in moving dunes (p>0.05).4. The main species composition of seedlings was annual and biennial herbs. Seedling density in fixed dunes was largest (7.2plant / m~2), lowest in semi-fixed dunes (2.4plant / m~2). From fixed dune to moving dune, the species numbers and the density of seedlings reduced.5. A small number of seedlings emerged under each sand dunes in April, seedling emergence was high in June, only small numbers or no seedling emerged in September. The spatial distribution of seedlings was uneven.6. Seedlings mortality was largest in April under each type of sand dunes. It was lowest in June in fixed dunes and semi-fixed dunes. On each period seedling mortality was high in moving dunes. Seedling mortality was irregular in flat dunes. Spatial distribution of seedling mortality was uneven. 7. There were obvious similarities between soil seed bank and aboveground vegetation in fixed dunes, semi-fixed dunes and flat dunes, but there was no obvious similarity in moving dunes. There was no similarity between seedlings and aboveground vegetation in fixed dunes. The composition of the seed bank and the seedling had proved great correlated in each sand dune.