科研之友
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摘要
The sustainability of hydrologic ecosystem services (freshwater benefits to people generated by terrestrial ecosystems) is challenged by human modification of landscapes. However, the role of landscape heterogeneity in sustaining hydrologic services at scales relevant to landscape management decisions is poorly understood. In particular, the relative importance of landscape composition (type and proportion of land cover) and configuration (spatial arrangement of cover types) is unclear. We analyzed indicators of production of three hydrologic services (freshwater supply, surface and ground water quality) in 100 subwatersheds in an urbanizing agricultural landscape (Yahara Watershed, Wisconsin, USA) and asked: (1) How do landscape composition and configuration affect supply of hydrologic services (i.e., does spatial pattern matter)? (2) Are there opportunities for small changes in landscape pattern to produce large gains in hydrologic services? Landscape composition and configuration both affected supply of hydrologic services, but composition was consistently more important than configuration for all three services. Together landscape composition and configuration explained more variation in indicators of surface-water quality than in freshwater supply or groundwater quality (Nagelkerke/adjusted R-2 : 86%, 64%, and 39%, respectively). Surface-water quality was negatively correlated with percent cropland and positively correlated with percent forest, grassland and wetland. In addition, surface-water quality was greater in subwatersheds with higher wetland patch density, disaggregated forest patches and lower contagion. Surface-water quality responded nonlinearly to percent cropland and wetland, with greater water quality where cropland covered below 60% and/or wetland above 6% of the subwatershed. Freshwater supply was negatively correlated with percent wetland and urban cover, and positively correlated with urban edge density. Groundwater quality was negatively correlated with percent cropland and grassland, and configuration variables were unimportant. Collectively, our study suggests that altering spatial arrangement of land cover will not be sufficient to enhance hydrologic services in an agricultural landscape. Rather, the relative abundance of land cover may need to change to improve hydrologic services. Targeting subwatersheds near the cropland or wetland thresholds may offer local opportunities to enhance surface-water quality with minimal land-cover change.
- 出版日期2015-11
