Improved methods for quantifying potential nutrient interception by riparian buffers

Abstract

Efforts to quantify the effects of riparian buffers on watershed nutrient discharges have been confounded by a commonly used analysis, which estimates buffer potential as the percentage of forest or wetland within a fixed distance of streams. Effective landscape metrics must instead be developed based on a clear conceptual model and quantified at the appropriate spatial scale. We develop new metrics for riparian buffers in two stages of increasing functional specificity to ask: (1) Which riparian metrics are more distinct from measures of whole watershed land cover? (2) Do functional riparian metrics provide different information than fixed-distance metrics? (3) How do these patterns vary within and among different physiographic settings? Using publicly available geographic data, we studied 503 watersheds in four different physiographic provinces of the Chesapeake Bay Drainage. In addition to traditional fixed-distance measures, we calculated mean buffer width, gap frequency, and measures of variation in buffer width using both ''unconstrained'' metrics and ''flow-path'' metrics constrained by surface topography. There were distinct patterns of relationship between watershed and near-stream land cover in each physiographic province and strong correlations with watershed land cover confounded fixed-distance metrics. Flow-path metrics were more independent of watershed land cover than either fixed-distance or unconstrained measures, but both functional metrics provided greater detail, interpretability, and flexibility than the fixed-distance approach. Potential applications of the new metrics include exploring the potential for land cover patterns to influence water quality, accounting for buffers in statistical nutrient models, quantifying spatial patterns for process-based modeling, and targeting management actions such as buffer restoration.

Landscape Metrics and Indices: An Overview of Their Use in Landscape Research

“…Weller et al (1998) developed and analyzed models predicting landscape discharge based on material release by an uphill source area, the spatial distribution of a riparian buffer along a stream, and retention within the buffer, and found average width to be the best predictor of landscape discharge for unretentive buffers. Baker et al (2006) quantified the effects of riparian buffers on watershed nutrient discharges by using, in addition to traditional fixed-distance measures, mean buffer width, gap frequency, and measures of variation in buffer width using both "unconstrained" metrics and "flow-path" metrics constrained by surface topography.…”

Applying additive modelling and gradient boosting to assess the effects of watershed and reach characteristics on riverine assemblages

“…More effective measures of the spatial configuration of land uses and quantitative measures of riparian conditions may improve model fits (Baker, Weller & Jordan 2006). Additionally, the MBSS measures of benthic habitat condition were largely qualitative (e.g.…”

Submerged macrophyte biomass distribution in the shallow saline lake Fuente de Piedra (Spain) as function of environmental variables

“…The use of fine scale mapping of wetlands is useful for analysing variability within individual wetlands and assessing the source of variability (Feldmann & Nõges, 2007). This factor is relevant for a suitable management, conservation or restoration of these areas (Baker & al., 2006). Aquatic macrophyte distribution has been related to many different environmental factors (Pokorný & Kevět, 2004).…”