小尺度乡村景观生态评价及重构研究

Ecological evaluation and reconstruction of fine-scale rural landscape

  • 摘要: 本文旨在小尺度上对乡村景观进行生态化评价, 辨识乡村景观建设的主要生态环境问题。在北京市大兴区、河北省曲周县和江苏省常熟市各选取1个研究区, 基于高分辨率遥感影像, 通过实地野外调查建立小尺度景观数据库。从景观空间结构和属性两方面进行评价, 采用情景分析研究乡村景观植被建设潜力。研究结果显示, 不同研究区整体上形成高度相似的网格化景观格局。线状景观组成在3个区域间差异显著, 注重田埂、田间路、防护林和沟渠的建设以维持农田景观多样性。农田防护林普遍存在主林带间隔过大的问题。农田基础设施地表过度硬化成为当前建设模式突出的生态问题, 在大兴区和常熟市分别达到28.46%和56.19%。防护林在林木覆盖率与绿量评价上显示出不弱于面状林地的重要性, 但面临结构简单、树种多样性低下、残缺断带率高达18%~38%的不足。情景评价显示线状植被具备较大的建设潜力, 合理规划能有效提升乡村林木覆盖率0.58%~1.16%、增加绿量2.22%~19.59%。本研究表明, 小尺度评价能辨识出乡村景观建设所面临的主要生态环境问题以及生态景观建设方向。

     

    Abstract: Strong demands for rural landscape development have taken into account of environmental issues related to sustainable development. The objective of this paper was to evaluate the main ecological effects of fine-scale rural landscape construction projects. Local landscapes boundaries, land uses and attributes were identified in a field survey with the help of high-resolution satellite images. Landscapes with least edge length over 2 m were classes as patches. These landscapes contained eight land use types, including farmlands, orchards, forests, grass, construction lands, roads, waters and others. Landscapes with least edge length between 0.5 m and 2 m were classed as linear landscapes. Such landscapes included vegetations, field roads, field ridges and ditches. All the field survey data were digitalized into a database in ArcGIS. Evaluation of landscape patterns and attributes was based on the rural landscape database composed of patches and linear landscapes. Landscape attributes contained land pavement and vegetation. Vegetation improvement potential was analyzed in three scenario conditions - basic, standard and optimal scenarios. Case studies were conducted in Daxing Region of Beijing City, Quzhou County of Hebei Province and Changshu City of Jiangsu Province. The study showed that current rural landscape construction projects seldom considered environment issues and had caused negative effects on landscape patterns and attributes. Simple block landscape patterns built in rural landscape construction projects eliminated landscape characteristics among different regions, forming similar landscapes in different areas. Field roads, ditches and field ridges were important linear landscapes with high densities in all three areas. Management patterns of shelterbelts were bad as interval distances between main shelterbelts were always larger than required optimal length for wind prevention. Over use of impervious surface pavements was a critical environmental risk in rural infrastructure construction. This risk was more serious in rural areas with strong economic support than in areas with weak economic investment. Excessive impervious surface pavements such as roads had reached 28.46% and 56.19% in Daxing Region and Changshu City, respectively, while it was only 5.6% in Quzhou County. Based on the evaluation of wood-cover and live vegetation volume, linear shelterbelt was nearly as importance as wood-plots at the local scale. Shelterbelts faced risks of simple vegetation structure, low tree species diversity and missing shelterbelt in range of 18% 38%. Simulation of the basic, standard and optimal scenarios showed a large potential for the improvement of wood-cover and live vegetation volume in rural areas through planting linear vegetation. Land use pressure was not simulated for linear vegetation distributions in marginal lands along roads, ditches and river banks. Through legitimate and appropriate planning and construction, wood-cover potentially increased by 0.58% 1.16% while live vegetation volume increased by 2.22% 19.59% under the standard scenario. Furthermore, the optimal scenario had higher growth of wood-cover and live vegetation volume. It was important to pay more attention to linear vegetation, including shelterbelt, in rural landscape planning for purpose of ecological improvement. The study revealed that evaluation at local scale was efficient in quantitatively identifying the shortcomings of current local landscape in terms of ecological conservation.

     

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