Analysis On The Spatial Heterogeneity Of Soil Seed Bank About The Southern Gurbantunggut Desert

Gurbantunggut desert is China's largest fixed and semi-fixed desert.But in recent years, excessive reclamation around the desert and other human actions, such as oil exploitation in the desert hinterland, led to death and degradation of large areas of vegetation. The study area of this paper is Southern Gurbantonggut desert. According to the size of the vegetation coverage, the study area is divided into three parts: east, central, west.We studied 54 sand dunes for soil seed bank research. Every sand dune was divided into seven different positions(the foot of the windward slope, the lower windward slope, the upper windward slope, the top, the upper leeward slope, the lower leeward slope, leeward slope bottom). Next, two Microhabitats——the open area and shrub understorey were studied in every sand dune position. Then, we sampled the 0-3cm ,3-6 cm ,6-10cm layer of soil in different situations to study the size, structure and species composition characteristics of soil seed bank. Based on the ground vegetation survey and adopting correlation analysis method, this work can provide a understanding of the relationship between vegetation and soil seed bank for exploring their potential role in the vegetation restoration of the Gurbantunggut Desert. The results are as follows:(1) Most seeds were found at depths in the range of 0–6cm and decreased with increasing burial depth. At the same depth, the difference was significant between east and central as well as east and west,while the difference was not significant between central and west. From the perspective of species composition of vertical stratification, species number decreased with increasing burial depth. From the same depth, species number of seed germination in east are greater than the central and western. These species, Corispermum lehmannianum , Salsola praecox Litv, S.ruthenica Iljin, Schismus arabicus Nees and A.ammophilus kar.et kir,germinated in every vertical stratification of soil.(2) Seed germination numbers under the canopy account for 61.3% of the total soil seed bank amounts,and in the open areas account for 38.7%. Seed bank density under the canopy showed greater than the open areas. However, from the eastern, central, west three regional point of view, seed bank density in central under the canopy was significantly richer than in open spaces ,and the difference was not significant in east and west.The species numbers of soil seed bank under the canopy were more than bare ground conditions. Seed bank density under the canopy from east to west as followed: east> Central> West,while in the open areas: east> Central, east> West ,but Central=West. These species,Corispermum lehmannianum , Salsola praecox Litv, S.ruthenica Iljin, Schismus arabicus Nees, A.ammophilus kar.et kir, Erodium oxyrrhynchum and S.glauca(Bge.) Bge , germinated under the canopy and in the open areas.(3) In whole southern desert, soil seed bank density in different sand dune positions is very different.The ordination as follow: the bottom of the windward slope> the bottom of the leeward slope >the lower leeward slope> the upper leeward slope>the lowe windward slope> Top> the upper windward slope. The difference significance analysis indicates that: the difference among seven positions was remarkable (p <0.05). In east, or in central ,or in west, the ordination of soil seed bank density at different sand dune positions is very different from the whole southern desert, but the upper part of the windward slope has the smallest seed density. On the soil seed bank species composition point of view, the upper leeward slope has the greatest number of species germination, and the bottom of the leeward slope has the least number. In addition to the bottom of the windward slope, the species numbers germinated in other slope positions were that the eastern was greater than the central and the eastern was greater than the western, while there is no obvious regularity between the central and western comparison.(4) The similarity between seed banks and above-ground vegetation was 27.6% in the eastern region, and 23.6% in the central region ,and 18.8% in the western region. This showed that the above-ground vegetation had positive correlation with soil seed banks.