国家级自然保护区土地覆盖类型转换趋势

国家为了防止生态系统恶化、保护自然栖息地及其生物多样性,到2010年底已建立2588 个自然保护区,总面积达 149.44×10⁶hm²,超过中国陆地总面积的15%。土地覆盖变化作 为导致生物多样性变化的首要因素,直接影响生态系统的结构和功能。本文选取180个国家级 自然保护,总面积44.71×10⁶hm²,占自然保护区总面积的29.9%,全国陆地面积的4.7%,根 据各保护区的生态系统特征和主要保护对象,将其划分为森林生态系统、草地生态系统、湿 地生态系统、珍稀动物、珍稀植物、地质和古生物遗址、以及荒漠生态系统7类自然保护区类 型,并在此基础上按东北、华北、华东、中南、西北及西南6个大区对其进行空间分析。论文 构建土地覆盖类型转换方向判别指数模型,运用生态多样性模型和斑块连通性模型,对各大 区内各类国家级自然保护区及其核心区、缓冲区和实验区的土地覆盖转换趋势进行计算。结 果显示,在20世纪80年代后期-2005年时段内,180个国家级自然保护区的土地覆盖转换强度 整体呈减缓趋势,西南地区的平均转换强度最大,而华东地区的平均转换强度最小。在各类 国家级自然保护区中,除了森林生态系统保护区外,其他各类型保护区的土地覆盖都存在逆 向转换,但逆向转换速率总体呈减缓趋势。国家级自然保护区的核心区土地覆盖逆向转换的 速度平均为0.16%/10a减少,其土地覆盖景观格局相对于缓冲区的和实验区更为稳定。生态多 样性指数和斑块连通性指数模型计算显示,国家级自然保护区土地覆盖景观格局的生态多样 性和斑块连通性在1995-2005年总体呈上升趋势。另外,各大区国家级自然保护区与非保护区 的土地覆盖转换强度对比显示,保护区土地覆盖转换强度整体上小于非保护区的土地覆盖转 换强度。总之,分析结果表明,国家级自然保护区的土地覆盖转换处于良性变化趋势,尤其是在1995-2005年期间,保护区内的土地覆盖类型及分布逐渐趋于正向转换和稳定态势。

Transition Trends of Land-cover in National Nature Reserves of China

A large number of nature reserves have been established in China aiming to prevent ecosystem degradation, protect natural habitats and conserve the biodiversity within the habitats. By the end of 2010, a total of 2588 nature reserves has been established in China and their total area was 149.44 million hectares, covering over 15% of China's total land area. As the primary driver of biodiversity change, land-cover change has direct effect on ecosystem structures and functions. Thus, a quantitative analysis of changes in the land-cover of nature reserves is a critical step for evaluating the effectiveness and improving the management policies of nature reserves. In terms of the ecosystem characteristics and its major protected objects, 180 National Nature Reserves (NNRs) are chosen and classified into 7 types in this paper. A Land-cover Transform Direction Index (LTDI) is developed on the basis of the contribution of each land-cover type to maintaining the ecosystem stability. In Northeast China, North China, East China, South China, Central-southern China, Northwest and Southwest China, LTDI is used to calculate the transition trend of land-cover in the core zone, buffer zone and experimental zone of each NNRs type during the period from the late 1980s to 2005. The results show that the mean transition rate of all selected NNRs types has become lower during the two decades. The land-cover transform rate of Southwest China was the largest, while that of East China was the smallest among the six regions. The mean positive and negative transform rates of land-cover in all core zones decreased by 0.69% and 0.16% respectively. The landscape pattern of land-cover in the core zones was more stable than that in the buffer zones and the experimental zones. The land-cover transformed rate of NNRs was less than that of Non-NNRs in general. Furthermore, the ecological diversity and patch connectivity of land-cover in the whole selected area increased generally during the period 1995-2005. In summary, the land-cover of NNRs in China has a beneficial change trend after the NNRs were established, especially during the period from 1995 to 2005.