Vegetation Cover Change And Its Stability In Shapotou National Nature Reserve,Ningxia

Arid desert area is the connection between desert ecosystem and oasis ecosystem, and the important place of material recycling, energy conversion and transmission of information. Vegetation degradation and disappearance, soil salinization, reducing animal resources and other issues become more and more serious, which pose a threat to the survival of the human environment. Through the research on vegetation health status and evolution in the arid desert nature reserve, assessing the impact on ecological stability and exploring the sustainable development mode of harmonious coexistence of man and nature. It has an guiding significance for the sustainable management of protected areas.In this paper, based on the actual situation of remote sensing image data, and combined with the vegetation growing season changes, the remote sensing images from 1990 to 2011 (1990,2001, 2007,2011) were used to analysis from vegetation, landscape and community three levels in Shapotou National Nature Reserve located in the southeastern edge of the Tengger Desert. Firstly, extract the dynamic change information of fractional vegetation coverage and vegetation types, and analysis the stability of the dynamic changes of vegetation coverage in brief. Finally, evaluate the stability of key vegetation communities in detail. From the studies, the main conclusions are as follows:(1) Due to the particularity of protected areas unique geographical location, under the transformation of human impact, vegetation distribution pattern presented "the east and south was high and the west and north was low" characteristics. The high-level vegetation coverage area was increased, the low-level vegetation coverage area was decreased. The fractional vegetation coverage presented first decreased and then increased trend of fluctuations, vegetation restoration area was larger than the degenerated with a "local improvement, a small amount of deterioration, most remain unchanged" characteristics. Vegetation restoration was given priority to with moderate improvement, improved significantly poorer, and vegetation restoration is given priority to with slight degradation, moderate degradation.(2) Vegetation cover types of protected areas could be divided into plantation, scrub, meadows, and cultivated crops four categories, covering an area of high to low plantation>shrub> cultivated crops> meadow. Changes in vegetation types could be divided into two phases: 1990-2001, in addition to increasing crop cultivation area, the other types of coverage were reduced.2001-2011, the plantation, scrub, cultivated crops area showed an increasing trend, meadow area to reduce volatility. The stability of natural vegetation types in scrub plaque was the best, meadow metastable. The stability of cultivated vegetation types in shelterbelt was the best, cultivated crops metastable, timber forests unstable.(3) Research on the key community biodiversity in protected areas showed that species composition was simple and extremely uneven. The dwarf shrub layer held an absolute advantage status with a higher stability. Herb layer was more easily influenced in precipitation and the change of seasons, the stability was low. Due to the species diversity of desert ecosystem was not very complex, which made the shrub layer an extremely remarkable ecological status and played an irreplaceable role. The community stability and ecological function were mainly determined by the dominant species in the shrub layer, which means the loss of species and community composition change would cause huge impact to the arid desert ecosystem.