宁夏农牧交错带村域景观演替及驱动机制

人类活动与景观格局的关系及其调控,一直是景观生态学研究的核心领域之一。农牧交错带因其环境波动、土地宜农宜牧和政策摇摆,自然生态和地方文化逐渐式微,保护和恢复现有的半自然景观以及由此产生的生物、生态和文化等功能的任务越来越紧迫。本研究以位于农牧交错带的宁夏盐池县皖记沟村为对象,运用遥感资料和访谈调查、地学考察相结合的方法,分析1964—2019年景观变化特征,探讨其景观演替规律及其自然和社会驱动机制,以及景观类型之间的互作机制。结果表明: 研究期间,皖记沟村由草地、耕地、沙地为主的景观结构演变为以草地、灌木林地、沙地、耕地为主的景观结构,由景观功能分离竞争向初步整合转变,形成了草地-耕地-沙地-灌木林地等确定的演替路径。景观演变的主要驱动机制是政策、人类需求和环境的综合作用。政策往往通过大型的、集中的人类活动促进景观发生改变,而环境通过生态系统内在驱动力,促使景观朝着与本底条件相适应的方向演替。景观演替的主要机理是土壤物理结构变化引起的土壤水分变化以及能适应新环境的植被变化。在资源密度较低的农牧交错带,景观功能分离是引起土地沙化的主要原因之一,景观功能的整合、协同大大缓解了生态恶化的局面。将景观分离竞争转化为景观共生,实现景观类型的互补乃至与外来资源的整合,是维持农牧交错带可持续发展的关键途径。

Village-level landscape succession and its driving mechanism in the agro-pastoral ecotone of Ningxia,China

The relationship between human activities and landscape patterns and its regulation are one of the core fields in landscape ecology. The ecological conditions and local cultures of agro-pastoral ecotone are gradually wea-kening due to environmental fluctuations, land-use characteristics (suitable for both farming and grazing), and unstable policy. Therefore, protecting and restoring this semi-natural landscape and the resulting biological, ecolo-gical and cultural functions are becoming increasingly urgent. Here, by combing remote sensing data with interview survey and geographic investigation, we characterized the landscape changes (1964 to 2019) of Wanjigou Village in Yanchi County of Ningxia Hui Autonomous Region, which lay within the agro-pastoral ecotone. We further explored the rules of landscape succession and the underlying natural and social mechanism, as well as the interactions between landscape types. Results showed that Wanjigou Village had been subjected to a succession from the landscape characterized by grassland, arable land and sandy land to that characterized by grassland, shrub land, sandy land and arable land. The change from the competition of landscape function separation to the preliminary integration had formed a definite succession path for grassland-arable land-sandy land-shrub land. The main driving factors were a synthesis of policy, human needs, and environment. Policy often promoted landscape change through large-scale and intensified human activities, while environment promoted landscape succession through internal driving force of ecosystem toward a mutual adaption between landscape and the innate conditions. The driving factors of landscape succession were soil moisture variations caused by the change of soil physical structure, and vegetation change in adapting to new environment. In agro-pastoral ecotone with low resource density, the separation of landscape functions was one of the main reasons for land desertification. The integration and coordination of landscape functions greatly alleviated the situation of ecological deterioration. The critical path to maintain sustainable development of agro-pastoral ecotone was to achieve complementation among landscape types and even integrating with external resources by transforming landscape separation competition into landscape symbiosis.