Zonation of Vegetation on Depositional Area of Blowout in Hulun Buir Gassland
呼伦贝尔沙质草原风蚀坑积沙区的植被分带性

Three types of modem blowouts including simple blowout, compound blowout on level grassland and simple blowout on stabilized dune are identified in sandy grassland of Hulun Buir. We investigate the morphology and vegetation distribution of sand deposit of blowouts and the results indicate that the distribution of plant species has a characteristic of zonation and species vary with the morphology and scales of sand deposit. The projected configuration of sand deposit of individual blowout on level grassland is tongue-shaped. From the edge of blowout to primary grass- land there are three regular crescent-shaped plant zonations that were sequentially dominated by the species of Agriophyllum punger, ,Agropyron cristatum and Thymus mongolicu with sand transport direction. The depositional area of combined blowout are dismembered by the dune with slipface, bare tongue-shaped sandy zonation, crescent-shaped plant zonation of Calamagrostis epigejos following wind and stripped zonation dominated by Agropyron cristatum which are distributed in the two-sides of the two zonations on level grassland. On stabilized dune the bare depositional area of blowout that is tongued-shaped passes through the zonations of Rosa davurica and Caragana microphylla that grew on dune before the appearance of blowout and extends to primary The leeward of bare depositional area is occupied by crescent-shaped zonation of C, grassland. epigejos. Analyzing the factor of vegetation zonation,we found there is a cubic equation correlation between Shannon-Wiener index and burial depth of sand, which suggests that the depth of deposition may be the major factor in zonation. These results demonstrate that the vegetation zonation is induced by sand-wind activity on sandy grassland. of sand deposit of blowout, the primary grassland v verse succession.