甘肃安西极旱荒漠国家级自然保护区南片植被长势与保护成效

以甘肃安西极旱荒漠国家级自然保护区南片为研究案例,借助高分辨率遥感影像和GIS技术,结合具体的植被类型和功能区划,分析了2000年到2010年间自然保护区内植被长势趋势的变化。结果发现:(1)11年来各植被类型,尤其是以骆驼刺、芦苇、芨芨草为主的天然草地植被表现出了较好的长势和增长的趋势;(2)核心区和缓冲区内不存在退化的植被类型,表明自然保护区基本实现了保护目的;(3)退化的植被位于实验区的布隆吉村、桥子村和双塔村,面积为1319 hm2,占比为0.31%。由此可见甘肃安西极旱荒漠国家级自然保护区南片植被保护成效明显。将植被长势趋势分析同自然保护区功能区划及植被类型相结合,希望有助于识别保护要点,以便为植被保护成效评价提供参考。

Vegetation growth and conservation efficacy assessment in the Southern Part of the Gansu Anxi National Nature Reserve in Hyper-Arid Desert

Deserts are vulnerable ecosystems formed under severe environmental conditions, and climatic anomalies and human disturbance can have irreversible impacts on wild animals, plants, and the natural environment of these ecosystems. Desert ecosystems perform irreplaceable eco-service functions, providing protection against wind, stabilizing sand, acting as biogeographic barriers, and promoting the conservation of biodiversity. Moreover, vegetation plays a crucial role in the assessment of ecological changes. Accordingly, by analyzing changes in vegetation, ecological threats can be identified and their severity quantified, thus helping to assess conservation efficacy in nature reserves. China is one of several countries worldwide suffering from severe desertification over vast areas, that is both extensive and complex. Accordingly, it is critical to understand conservation efficacy in the desert ecosystems of China''s nature reserves. The Gansu Anxi National Nature Reserve in Hyper-Arid Desert (GANNR) is the only reserve in China established to protect hyper-arid desert ecosystems and their biodiversity; it is located in Guazhou County in the western part of the Hexi Corridor, Gansu Province. GANNR covers approximately 8000 km², and thus accounts for one third of the total area of Guazhou County. The reserve separates the Kumutage and Badain Jaran deserts, sheltering the Hexi Corridor oasis and preventing sandstorms. Accordingly, it plays a critical role in biodiversity conservation and regional eco-safety. GANNR is divided into two parts: the northern and southern reserves. As the Chinese government has implemented its western development strategy, some key national projects have extended across the northern part of GANNR, including infrastructure for west-east natural gas transmission, west-east power transmission, and the Lan-Xin railway. In this study, we selected the southern part of GANNR as our study area for several reasons: (1) the vegetation cover and species richness are higher here than in the north; (2) typical temperate desert vegetation such as Reaumuria soongorica, Salsola passerina, Sympegma regelii, and Ephedra przewalskii can be found and assessed in the south; and (3) some villages are located in the southern part of our study zone. We analyzed trends in vegetative growth from 2000 to 2010, using RS and GIS by combining vegetation type and functional zoning maps. The vegetation type map was created using a high-resolution remote sensing image, which was acquired from the ZY-1-02C satellite in August 2012. This image had a spatial resolution of 2.36 m, after processing in ENVI 5.0 using orthorectification and the Gram-Schmidt method. Regression analysis of NDVI and elapsed time revealed the vegetation growth trend for each vegetation type in different functional zones. The results show the following: (1) each vegetation type exhibited increased growth over time, with an increasing trend during the 11-year period. This was particularly true for the natural grassland, which included Alhagi sparsifolia, Phragmites australis, and Achnatherum splendens; (2) no degraded vegetation types were found in either the core zone or the buffer zone, indicating that the GANNR administration achieved their protection goal; and (3) degraded vegetation types were found in the Bulongji, Qiaozi, and Shuangta villages, covering an area of 1319 hm²; this corresponds to just 0.31% of the study area. Although we have clearly demonstrated the vegetation conservation efficacy in GANNR, we also make the following suggestions: (1) adjust the functional zoning, such that the area containing Ephedra przewalskii is incorporated into the buffer or core zones; and (2) strengthen supervision around the villages to maintain the grassland conservation results achieved previously by constructing a fence to return grazing land to grass. We hope that this study will be beneficial to the GANNR administration, and will act as a reference for future vegetation conservation efficacy assessments.