Vegetation-environment Relationship And Its Implications On Ecological Restoation For Sandy Region In North Of Ordos Plateau

Environmental factors and vegetation form a dynamic balance between feedback and response in the globe surface. But the dynamic balance was broken constantly by all kinds of causes, which changed the structure and function of the ecosystem, and deteriorated the living environment.Vegetation-environment relationships were analyzed by different scale and view in the sandy region in North of Ordos Plateau, a representative ecological transitional area. Based on the relationships, ecological restoration recommendation was presented for different subarea. After preliminary analysis, results were got as following:(1) Flora: There are 63 families, 236 genera, 427 species and 19 variations vascular plants in the study region, which in the composing of families, Compositae, Gramineae, Leguminosae and Chenopodiacea are preponderant, while in the composing of genera, Artemisia, Astragalus, Chenopodium, Polygonum are preponderant. The distribution types of family and genus are mostly temperate distribution. With the unique climatic and geographic conditions, the region formed the flora system that composing dominantly the perennial herbage of mesic and xerophytic, characterized by obvious layer of annual or biennial herbage and relatively developed shrub and semi-shrub. And the flora has substitute attribute.(2)Spatial distribution of vegetation: Confirmed the Kubuqi sandy region area (20394 km2) for the first time in 2002 by 3S techniques. As a whole, the vegetation background of the study region was psammophyte community with the essential species of Artemisia ordosica, and other community types mosaiced among it. Thus formed the particular and representational vegetation pattern. Both the zonation and psammophyte vegetation have distinct law of segregation from east to west and from south to north, i.e. from east to west formed alternative distribution pattern of typical steppe, desert steppe and steppe desert, and from south to north formed that of zonation vegetation, desert-sand vegetation and intrazonal low wet land vegetation + artificial vegetation.(3) Subarea of vegetation-climate and dynamic of vegetation pattern: The zonation vegetation and psammophyte vegetation in the 4 subarea of vegetation-climate compartmentalized by Ivanovii humidity index both characterized obviously by climate. In each subarea of vegetation-climate from east to west, not only the area of Form. Artemisia ordosica shrinked constantly, the substitute pattern of association was apparent. From the end of the seventies of the 20th century to the beginning of 21st century, the warm-humiditization of climate and revegetation caused the area of traveling sand and semi-mobile sand in thesandy region in North of Ordos plateau to decrease and the area of steady psammophyte vegetation composed mainly by Artemisia ordosica to increase.(4) The distribution characteristics of the content of soil under different vegetation types: The difference of the content of soil under different vegetation types in the study region was obvious. The soil condition at the region where steppe plant species presented was better than that at the region where psammophyte vegetation distributed. The soil was infertile and saline-alkali seriously in the ecotone between the Kubuqi Desert and the riverbank of the Yellow River. With the depth deeper, the soil trended to be more infertile and the soil salt content to be decreased. At a small scale, the distribution evenness of the soil moisture and soil salt under the artificial vegetation was far better than that under the natural vegetation. The soil salt and soil moisture under the studied 10 vegetation types mostly had relatively higher spatial correlation.(5) Characteristics of atmospheric precipitation-soil moisture-ground water for different vegetation types: The relationships among the atmospheric precipitation, soil moisture and ground water at the edge of desert characterized by lower soil moisture and biggish variance between layers, lower groundwater level but steady, fuzzy relations between soil moisture and ground water, quick movement in soil of atmospheric precipitation, which were visibly different from that at the ecotone which between desert and oasis, and that inside the oasis. The soil moisture under the vegetation at the Yellow River low step mulching sand, under the vegetation between sand dunes, and under the vegetation at the flat sand and stabilized dune decreased in turn. Precipitation has great importance on the increase of the soil moisture, and such change trend has a consanguineous relation with the topography and vegetation type, and the difference was especially obvious between different vegetation types.(6) Effects of grazing disturbance on saline grassland and soil characteristics: Grazing disturbance caused the spatial heterogeneity to increase further, the heterogeneity was the vegetation distribution mosaic pattern of Nitraria sppAvtas and low step meadow between dunes at saline grassland in study region. And grazing disturbance decreased the vegetation cover, species abundance and species diversity at saline grassland, but it had not obvious effects on species evenness. Heavy grazing caused the dominant species succession, and the decrease of dainty species. Shrub had functions protecting annual herbage for some certain. Continuous grazing was a stable structure factor that impacted the spatial distribution, weakened the spatial heterogeneity and strengthened the evenness of soil water and salt in saline grassland. And thus function could not be ignored in the soil water and salt movement and redistribution in saline grassland.(7) Recommendations of ecological restoration: Based on the studies above and based on thesubarea, analyzed the main ecological environment problems, discussed the construction objects and rules, and presented the construction contents and approaches to actualize.