| In Calleguas Creek Watershed, 61 unique stream reaches in agriculture, developed, and open space areas were randomly selected and sampled for fish, benthic macroinvertebrates, channel morphological features, and riparian cover. Using linear regression and analysis of variance statistics, we showed clear distinctions between land use classes and assessed the relative effects of each land use type. Macroinvertebrate taxa richness best differentiated between open space and modified land use classes. Open space sites exhibited higher pollution intolerant Ephemeroptera, Plecoptera and Tricoptera (EPT) taxa richness. We collected only one native fish species, Gila orcutti . The physical habitat assessments included quantitative in-stream habitat measurements (e.g., substrate, channel shape, bank conditions) and qualitative evaluation of riparian vegetation cover. Regression and ANOVA statistics revealed substrate composition, woody ground cover and channel wetted width as robust indicators differentiating between the three dominant land use classes. Open space sites exhibited more diverse substrate composition and riparian vegetation coverage. EPT taxa richness, percent cobble and coarse fine substrate, and woody ground cover exhibited the highest capacity for differentiating among the three land use classes. In addition, we conducted an exploratory investigation of the association between scale, land use cover and stream ecological condition. Using GIS, we applied three methods of defining land use boundaries in the watershed to evaluate the relationship between ecological condition and three land use classes. A 30 m resolution 1993 land cover of the watershed was re-categorized into open space, urban/residential, and agriculture, and overlaid with the available stream network layer. We created 100 m and 300 m radii buffer zones around each sampled stream site, identified two stream beltway zones with lengths of 1000 m and 3000 m, and created upstream sub drainages using digital elevation model data specific to the watershed. While EPT taxa richness did not respond significantly to the five spatial scales examined, substrate size and woody ground cover responded significantly to the semi-circle and beltway zone scales. These preliminary results are not complete but suggest local effects may be more important than regional level modifications in determining in-stream condition. |
