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LANDSCAPE INFLUENCES ON LAKE CHEMISTRY OF SMALL DIMICTIC LAKES IN THE HUMAN DOMINATED SOUTHERN WISCONSIN LANDSCAPE
Citation:
ALLEN, P. LANDSCAPE INFLUENCES ON LAKE CHEMISTRY OF SMALL DIMICTIC LAKES IN THE HUMAN DOMINATED SOUTHERN WISCONSIN LANDSCAPE. Presented at IALE Conference, Madison, WI, April 06 - 10, 2008.
Impact/Purpose:
Presentation at the IALE Conference
Description:
Changes in landscape heterogeneity, historic landcover change, and human disturbance regimes are governed by complex interrelated landscape processes that modify lake water quality through the addition of nutrients, sediment, anthropogenic chemicals, and changes in major ion concentrations. Current knowledge of how landscapes influence water resources comes primarily from stream studies. This study contributes to the small but growing body of research on the landscape ecology of lakes. Twelve lakes, similar in most respects except for surrounding landuse and landscape position, were sampled over a two year period for water quality proxies of nutrient enrichment and productivity; erosion and sedimentation; solutes, and anthropogenic chemicals. Nonmetric multidimensional scaling was used to evaluate how lakes varied across gradients of water and sediment chemistry and lake morphometry. Correlation and multiple regression analyses tested our assumptions (based on previous stream studies) about correlations between landuse and land cover; heterogeneity, and water quality proxies. Differences in chemistry among lakes were most correlated with lake depth which is related to landscape position and governed by geomorphology. These data show that in general, high proportions of forests and wetlands were correlated with desirable water quality characteristics (i.e. reduced sedimentation, nutrients and dissolved solids). Agriculture was positively correlated with nutrient enrichment and productivity, erosion and sedimentation, increased solute concentrations, and atrazine. High landscape interspersion and increased edge densities were also correlated with increased solute concentrations. Decreased shape complexity of the patches (area weighted mean shape index) was positively correlated with reduced water quality and agriculture. Water quality predictions based on landuse and landscape metrics were more often confirmed at larger (watershed) spatial scales. The affect of landscape position is a significant factor in interpreting impacts on lakes particularly at local scales and should be considered in future work. Results of this study suggest that landscape management goals for lake protection should include minimizing agriculture in riparian areas. Additionally, an increase in forest and wetland buffers at smaller (catchment and riparian) spatial scales, and an increase in forest connectivity at watershed scales should enhance the natural cleansing functions of both forests and wetlands and improve or maintain lake water quality.