The land-use legacy effect: Adding temporal context to lake chemistry

Sherry L. Martin, Daniel B. Hayes, Daniel T. Rutledge and David W. Hyndman

Limnol. Oceanogr., 56(6), 2011, 2362-2370 | DOI: 10.4319/lo.2011.56.6.2362

ABSTRACT: We investigated land use and land cover (LULC) effects, i.e., effects that perpetuate beyond an expected or perceived temporal endpoint, on the chemistry of 35 lakes in the Huron River Watershed, Michigan. Temporal changes in five time steps of LULC were represented by principal components, which were entered hierarchically into a multiple regression to predict water chemistry. We compared model fit using Akaike weights, and model predictive ability using R2, for models representing LULC from a single time up to models that included LULC from all five time steps. The regressions using only the most recent LULC provided the best fit for phosphorus species, but legacy models provided a better fit for all nine other lake water characteristics. Models for all species of nitrogen, calcium, silica, and sulfate showed an intermediate legacy effect and incorporated some historic LULC. Models for conservative ions showed the longest legacy effect, incorporating all five time steps, and had the highest explanatory power of all water chemistry characteristics in our study. Legacy timescales are likely influenced by biological reactivity: highly reactive elements had relatively short legacy timescales and conservative ions had the longest legacy timescales.

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