外来树种桉树引种的景观生态安全格局

以大面积桉树引种区云南省澜沧县为研究区,以自然栖息地和生物多样性的整体保护为目标,利用最小累积阻力模型开展了桉树引种的景观生态安全格局的定量研究.结果表明:(1)基于GIS技术和“成本距离加权”制图分析工具,将生物和景观等综合因素融入最小累积阻力模型,把“源”扩展的生态过程与景观格局结合起来,应用于桉树引种的景观生态安全格局构建中是可行的.(2)选择次生常绿阔林为保护“源”,地表覆盖类型、海拔、坡度、土壤质地和公路等为阻力因子,建立最小累计阻力面,识别了廊道、辐射道和战略点等生态安全格局组分；用最小累积阻力阈值划分了生态缓冲区、生态过渡区、生态边缘区、农业耕作区和居民生活区等生态功能区,并界定桉树禁止种植区和桉树可种植区,最终组合成两个方案的中级和高级景观生态安全格局.方案一,中级和高级安全水平的桉树可种植区面积分别占研究区面积的33.48％和19.27％.方案二,中级和高级安全水平的桉树可种植区面积分别占研究区面积的28.37％和15.17％.(3)从“源”的扩展效果、保护广度、管理成本、难易程度及生态环境和经济社会发展要求等方面评价,认为方案二的中级安全水平格局能够相对满足澜沧县对生态、经济发展的要求.研究结果为制定研究区生态安全策略提供参考.

Landscape ecological security pattern associated with the introduction of exotic tree species Eucalyptus

With rapid introduction of exotic trees, natural habitat loss and landscape fragmentation were aggravated in mountainous areas. Construction of landscape eco-security pattern can provide feasible option to prevent landscape fragmentation and to protect natural habitats and biodiversity. Since 2003, a large amount of exotic tree species, Eucalyptus has been introduced into Lancang county of Yunnan province. The Eucalyptus replaced the native forest, farmland, wasteland and other ecosystems, leading to serious natural habitat loss, landscape fragmentation and biodiversity threatening. In this paper, the large areas in Lancang County of Yunnan Province, where Eucalyptus have been extensively introduced were selected as the case study sites to examine the landscape eco-security pattern for Eucalyptus introduction by using the minimum cumulative resistance model. The results indicated: (1) it's feasible, based on the GIS and "cost distance weighing" mapping analysis tool, to construct the landscape eco-security pattern of Eucalyptus introduction by integrating the biological factors and landscape factors into minimum cumulative resistance (MCR) model and combining the "source" extended ecological process with Landscape pattern. This can be a reference approach to constructing the landscape eco-security pattern for the exotic tree introduction in other areas. (2) the components of ecological security pattern such as corridor, radiating routes and strategic point etc. indentified by the minimum cumulative resistances surface which were derived from the GIS-based and MCR model using land cover types, altitude, slope, soil texture and road etc. as resistance factors can preserve ecosystem functions in Eucalyptus-introduced and affect positively the species migration and diffusion in " protection source", which was secondary evergreen broad-leaved forest in natural habitat in this study. By using the minimum cumulative resistance threshold values, we divided the eco-buffer zone, eco-transition zone, eco-fringe zone, farming zone and residential zone for the landscape eco-security construction. We also defined the banned zone and planting zone for Eucalyptus plantation. The medium-security and high-security landscape eco-security patterns were developed on the basis of minimum cost but maximum ecological and economic benefit for the introduction areas in Eucalyptus plantation. To achieve this goal, there will be two schemes. In the first scheme, medium-security and high-security areas for Eucalyptus plantation account for 33.48% and 19.27% of total study areas. In the second scheme, medium-security and high-security areas for Eucalyptus plantation account for 28.37% and 15.17% of total study areas. (3) the second scheme of medium-security pattern could fit ecological and economic conditions of Lancang County better when compared these two schemes from the expansion effect of "source", protection range, management cost, difficulty level, eco-environment capacity as well as economic and social development. In the second scheme, the large and small patches of protection 'sources' were spaced in-between, and large patches can work well for protecting the species and ecosystems better, small patches could be settled foothold to protect distributed rare species or ecological niches. As the "source" patches were small and concentrated, the fragmentation was relatively low, so the protection and management of the "source" will be less difficult and costly. There were 22 corridors and combined circular, so the connectivity among "sources" was good. There were 6 radiating routes, meaning less opportunity for "sources" expansion. There were many strategic points of native tree species for improving the integrity of the "sources". All these results may provide some useful references for developing eco-security strategies in the study areas.