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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Land/Water Interfaces
TEMPORAL VARIATION IN THE RELATIONSHIPS BETWEEN LAND-USE AND STREAM CONDITIONS.
M.A. Estrada. Environmental Sciences and Resources Program, Portland State University, Portland, Oregon 97207
It is challenging to develop nutrient loading criteria and a trophic classification system in streams. The objective of this study is to assess the relationships among nutrients, algae, and watershed characteristics, and how these relationships may vary temporally between wet and dry seasons. Physico-chemical variables, benthic periphyton, and stream phytoplankton are being sampled monthly from 18 streams along a land-use gradent in the Northwestern Oregon Cascades Range. The initial correlation analysis of the first two sets of physico-chemical data indicates that the correlations between physico-chemical variables and land use during late summer (dry season) was weak, and as the rainy season began these correlations increased. Thus, the correlation between turbidity and TP was relatively low in September 2001 (r=0.04), and increased in November 2001 (r = 0.71). The correlation between percentage vegetation cover and in-stream variables (e.g., nutrients, temperature, conductivity and turbidity) increased from –0.46 to –0.68 (average). The initial results suggest that land-use, hydrology and interactions between these factors may all contribute to variation in nutrient loading, and their effects on lotic periphyton in streams.
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