Landscape influences on stream biotic integrity assessed at multiple spatial scales

Abstract

The biological integrity of stream ecosystems depends critically on human activities that affect land use/cover along stream margins and possibly throughout the catchment. We evaluated stream condition using an Index of Biotic Integrity (IBI) and a habitat index (HI), and compared these measures to landscape and riparian conditions assessed at different spatial scales in a largely agricultural Midwestern watershed. Our goal was to determine whether land use/cover was an effective predictor of stream integrity, and if so, at what spatial scale. Twenty-three sites in first-through third-order headwater streams were surveyed by electrofishing and site IBis were calculated based on ten metrics of the fish collection. Habitat features were characterized through field observation, and site His calculated from nine instream and bank metrics. Field surveys, aerial photograph interpretation, and geographic information system (GIS) analyses provided assessments of forested land and other vegetation covers at the local, reach, and regional (catchment) scales.The range of conditions among the 23 sites varied from poor to very good based on IBI and HI scores, and habitat and fish assemblage measures were highly correlated. Stream biotic integrity and habitat quality were negatively correlated with the extent of agriculture and positively correlated with extent of wetlands and forest. Correlations were strongest at the catchment scale (IBI with % area as agriculture, r 2 = 0.50, HI with agriculture, r 2 = 0.76), and tended to become weak and non-significant at local scales. Local riparian vegetation was a weak secondary predictor of stream integrity. In this watershed, regional land use is the primary determinant of stream conditions, able to overwhelm the ability of local site vegetation to support high-quality habitat and biotic communities.

Effects of isolation and environmental variables on fish community structure in the Brazilian Amazon Madeira-Purus interfluve

“…As basin 1 was different both in terms of distance and drainage direction, and there was no replicates for these differences, it was not possible also to analyze the relative effects of distance and drainage direction on composition, and to assess what of these factors would be responsible for the greater differentiation of the basin 1. Fish distribution is usually related to climatic, geomorphological, and historical factors (Roth et al, 1996;Poff and Allan, 1995). According to Hoeinghaus et al (2007), historical processes, such as speciation and dispersal, strongly affect local communities.…”

Quantifying the effect of catchment land use and water nutrient concentrations on freshwater river and stream biodiversity

“…Upper and lower confidence levels (95%) are depicted in dashed lines. Data are based on studies by Roth et al, 1996;Harding et al, 1998;Marchetti and Moyle, 2001;Joy and Death, 2004;and Schweizer and Matlack, 2005. Figure 4.…”

“…Note that the line of the EPT overlays the upper confidence level of the combined macroinvertebrate, fish and EPT regression line. Data are based on studies by Roth et al, 1996;Harding et al, 1998;Euliss and Mushet, 1999;Hall et al, 2001;Marchetti and Moyle, 2001;Sponseller et al, 2001;Bojsen and Jacobsen, 2003;Collier and Quinn, 2003;Harding, 2003;Joy and Death, 2004;Bruns, 2005;and Schweizer and Matlack, 2005. …”

Large‐scale relationships between basin and riparian land cover and the ecological status of European rivers

“…Various studies have demonstrated negative relationships between biological indices and the percentage of agricultural land in the catchment or gradients of agricultural intensity (Roth, Allan & Erickson, 1996;Walser & Bart, 1999;Cuffney et al, 2000). These impacts are dependent on the different categories of production: many authors designate intensive agriculture as a cause of degradation in stream habitats (Allan & Johnson, 1997;Allan, 2004).…”