Study On Structure And Ecological Function Of Artificial Vegetation In Southeastern Margin Of Maowusu Sand Land

Taking a whole view of the domestic researches on the artificial vegetation, most of them are concentrated on small scale, single object and simple contrast, the study on the establishment of an efficient, stable and optimization artificial vegetation model, on the methods of how to ensure the artificial vegetation develop efficiently and maintain the structure stable and the function sustainable development are lack of systemic research. Today comprehensively evaluating and effectively regulating the stability structure and ecological function of artificial vegetation is a hot research spot and need to be dissolved in the field of ecology and environment construction. Therefore, based on theories of landscape ecology, systems engineering and sustainable development, according to combing standard plot investigation and permanent plot observation, single technology and corresponding technology, located observation and experimental analysis, mathematical methods and computer technology, to analyze the structure configuration, ecological function and control technology of artificial vegetation of Yulin desert in the southeastern margin of Maowusu sand land, establish the comprehensive indexes system of ecological benefits evaluation, evaluate the ecological function of sand-binding and wind-controlling, put forward the reasonable structure, optimize allocation mode and control technology for different artificial vegetations, provide a theoretical foundation and technological support for implementation of anti-desertification project, all these work are very important and have a great significance in guiding the practice for the construction of ecological environment. The research results are innovative in some aspects, such as science, universality, relevancy and systemic aspect. The main conclusions show as following:(1) Taking the approach of level analysis, factor analysis and comprehensive evaluation model to comprehensively evaluate the vegetation site factors of Yulin desert in large scale, according to the comprehensive index to implement the site area division and the suitable tree species chosen, by using the gray interrelated analytical method to evaluate the main species suitability, the order of the shrub is H.scoparium(1.0) > Hedysarunlaeve(0.86) > Salix psammophila(0.84) > Caragana korshinskii(0.83) > Amorpha fruticasaL(0.77) > Sabina vulgaris(0.65), and the suitability order of the arbor is: Populus opera (1.0) > Pinus sylvestrisL.Var.MongoLicaLitvin(0.70) > Platycladus orientalis(L.) Franco(0.66) > Pinus tabulueformis Carr. (0.60) > Populus simonii Carr. (0.58). (2) Through the research of artificial vegetation succession and its mechanism from the views of vegetation community, landscape feature and dynamic change, the results show that Yulin desert vegetation has an obvious level synusia structure. According to the differences among the sites conditions, the vegetation can be divided into two major communities, Hedysarunlaeve community and Amorpha fruticasaL community. The advantage sand-binding vegetation is Hedysarunlaeve and Amorpha fruticasaL, the advantage of Caragana korshinskii and H.scoparium are less. The driving forces for the vegetation succession and landscape feature change are the change of moisture and the human activities. Under the destroy of the artificial vegetation, the process of the sand-binding vegetation succession is natural sparse herb stage — artificial shrub stage — artificial vegetation + natural vegetation stage — natural herb advantage stage, which made the vegetation synusia structure be more complex and the vegetation function be more stable.(3) Taking theory of mechanical dynamic simulation to do the systemic research on the structure configuration of artificial vegetation, proposing the reasonable vegetation coverage, the reasonable vegetation density and the reasonable vegetation structure based on the land resource, the water balance and the protection function propose. The reasonable coverage of artificial vegetation should be about 35%, and the whole coverage of all the vegetation should be about 70%. The reasonable densities of shrubs are: Salix psammophila 3621 strain/hm~2 , H.scoparium 763 strain/hm~2 , Hedysarunlaeve 4729 strain /hm~2, Amorpha fruticasaL 4892 strain /hm~2, Caragana korshinskii 3490 strain/hm~2. The reasonable structure of shelter belt vegetation should be sparse structure, the sparse rate of main belt should be 30-50% and the margin between two sparse rates of different synusias should not be exceed 15%, the space between main belts should be 150-200m and the space between sub-main belts should be 200-300m, the direction of the broad-belt should be perpendicular to the main wind direction, and the direction of the narrow-belt also should be more than 45° angle to the main wind direction. Base of those, select the best types of the structure distribution modes for the different site conditions, including sand-binding and wind-controlling forest 52 types, farmland shelter 18 types, timber forest 8, water resource shelter 9 types, road shelter 22 types.(4) Based on the evaluation on the each single biological effect of sand-binding and wind-controlling, local climate regulation, soil improvement, hydrology effect and biology effect, taking the approach of level analysis to form a comprehensive evaluation system, and taking a comprehensive evaluation model to evaluate the ecological benefit of the primary five sand-fixed shrubs, the result order is Hedysarunlaeve (40.81) > Amorpha fruticasaL (39.13) > Caragana korshinskii (37.43) > Salix psammophila (37.31) > H.scoparium (35.19) by the evaluate score. In the windward slope of the sand Hedysarunlaeve is the best, in the space between two sand Amorpha fruticasaL is the best, H.scoparium and Salix psammophila are both suitable in these two sites. Taking mixed forest can increase structural the stability and improve the eco-benefit.(5) The research on the artificial control technology shows that artificial vegetation can improve the forest environment and enhance the stability of structure and function. Stumping time is better to be arranged in winter or spring when the vegetation being dormancy, the interval between two stumping time should be about five years. Grazing should be taken circle with enclosure, and after the grazing the enclosure time should be more than two years. Spraying time is better to be arranged from the mid ten days of May to the mid ten days of June, the spraying plants mainly are H.scoparium, Artemisia, Astragalus adsurgens and Hedysarunlaeve, the seeding quantity of Hedysarunlaeve is 11.3～15.0kg/hm~2, H.scoparium is 15.0～22.5kg/hm~2 separately, and by mixing the seeding quantity is 7.5kg/hm~2. Planting time is better to be arranged in spring, taking techniques such as container breeding, deep pit, coverage, rhizogenic powder, water holding agent and so on, all these techniques can increase the seedling survive rate, especially for the evergreen trees and for the forestation in difficult site.