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Context <p>The effects of natural topographic characteristics and land-use patterns on riverine nitrogen (N) and phosphorus (P) levels are complex and scale-dependent in agricultural watersheds. Quantifying the individual and interactive effects of different landscape categories and determining their spatial scale sensitivities is helpful to develop effective landscape planning to mitigate nonpoint source (NPS) pollution; however, these effects have not been clarified.</p> Objectives <p>The aims are to quantify the multi-scale effects of landscape characteristics on riverine N and P levels, and to determine the spatial-scale sensitivity in impacts of topography, land-use composition, and land-use configuration on riverine N and P variations.</p> Methods <p>Topography and landscape pattern were quantified and riverine nutrient variations were observed in a subtropical agricultural watershed with 13 sub-watersheds. The influences of the land-use composition, land-use configuration, and topography on riverine N and P levels across multiple scales were analyzed by redundancy analysis, and their relative contributions and spatial scale sensitivities were determined by the variation partitioning analysis.</p> Results <p>(1) The landscape metrics at the 100&#xa0;m buffer scale could better explain the variations in riverine pollutant concentrations than at the 300&#xa0;m, 500&#xa0;m and catchment scales. (2) Among the three landscape categories, the spatial scale sensitivity of topography impact on riverine N and P levels was the most obvious. Topographic factors influenced water quality mainly through their interaction with land use (12.0–19.6%). (3) The land-use configuration was the most significant driver of the spatial variation in riverine N and P levels at each spatial scale (23.4–32.2%), and its influence was less sensitive to spatial scale changes. Promoting the integration of farmland into contiguous and large-scale management (IJI_<sub>far</sub>) at the 100&#xa0;m and 300&#xa0;m buffer scales, reducing the complexity of garden plot patch shapes (LSI_<sub>gar</sub>) at the 500&#xa0;m buffer scale, and improving the aggregation of residential land distribution (IJI_<sub>res</sub>) at the catchment scale could effectively mitigate riverine N and P pollution.</p> Conclusions <p>Land-use configuration is the primary driver of spatial variations in riverine N and P levels, exerting significant influence at each spatial scale. Thus, optimizing landscape configuration from multi-scale perspective could effectively manage NPS pollution in agricultural watersheds.</p>

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Multi-scale effects of topography and landscape pattern on riverine nitrogen and phosphorus nutrients in an agricultural watershed

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年5月29日

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  • Jianhong Wu,
  • Shengjia He,
  • Jun Lu

摘要

Context

The effects of natural topographic characteristics and land-use patterns on riverine nitrogen (N) and phosphorus (P) levels are complex and scale-dependent in agricultural watersheds. Quantifying the individual and interactive effects of different landscape categories and determining their spatial scale sensitivities is helpful to develop effective landscape planning to mitigate nonpoint source (NPS) pollution; however, these effects have not been clarified.

Objectives

The aims are to quantify the multi-scale effects of landscape characteristics on riverine N and P levels, and to determine the spatial-scale sensitivity in impacts of topography, land-use composition, and land-use configuration on riverine N and P variations.

Methods

Topography and landscape pattern were quantified and riverine nutrient variations were observed in a subtropical agricultural watershed with 13 sub-watersheds. The influences of the land-use composition, land-use configuration, and topography on riverine N and P levels across multiple scales were analyzed by redundancy analysis, and their relative contributions and spatial scale sensitivities were determined by the variation partitioning analysis.

Results

(1) The landscape metrics at the 100 m buffer scale could better explain the variations in riverine pollutant concentrations than at the 300 m, 500 m and catchment scales. (2) Among the three landscape categories, the spatial scale sensitivity of topography impact on riverine N and P levels was the most obvious. Topographic factors influenced water quality mainly through their interaction with land use (12.0–19.6%). (3) The land-use configuration was the most significant driver of the spatial variation in riverine N and P levels at each spatial scale (23.4–32.2%), and its influence was less sensitive to spatial scale changes. Promoting the integration of farmland into contiguous and large-scale management (IJI_far) at the 100 m and 300 m buffer scales, reducing the complexity of garden plot patch shapes (LSI_gar) at the 500 m buffer scale, and improving the aggregation of residential land distribution (IJI_res) at the catchment scale could effectively mitigate riverine N and P pollution.

Conclusions

Land-use configuration is the primary driver of spatial variations in riverine N and P levels, exerting significant influence at each spatial scale. Thus, optimizing landscape configuration from multi-scale perspective could effectively manage NPS pollution in agricultural watersheds.