Fractals in Nature: A Spectral Analysis of Nutrient Transport and Landscape Hydrology

The transport of phosphorus (P), a major source of pollution in freshwater ecosystems, is directly linked to the flow paths and travel time of water through a catchment. The objective of this research is to understand P movement for improved management of drinking water resources. Here we used spectral analysis to show the differences in long-term P transport trends between an active agricultural watershed (160 ha) and an abandoned agricultural forested watershed (85 ha) in the Catskills Mountains, NY, specifically, in Delaware County. The watersheds were close to each other, 6.4 km apart, so that hydro-meteorological differences were small. The results suggest interesting shifts in P transport behavior when historically fertilized land is abandoned and allowed to revert to forest. Spectral analysis, a long-term frequency domain time series analysis method, has been successfully used to analyze long-term time series data, quantify travel time distributions, and measure the watershed scale retardation factor for reactive solutes (Kirchner et al. 2000, Nature 43:524-527; Kirchner et al., 2001J. Hydrol. 254:82-101). Here we combined Spectral Analysis of nutrient data and water table fluctuations to provide a perpetual model of the watershed. We found that spectral analysis is a useful tool for analyzing long-term time series of water and chemical fluxes record for understanding ecosystem responses to disturbance and provide a in depth view of long-term effects of changing agricultural and natural resource management practices.