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META-ANALYSIS OF NITROGEN REMOVAL IN RIPARIAN BUFFERS
MAYER, P. M., S. K. REYNOLDS JR, M. D. MCCUTCHEN, AND T. J. CANFIELD. META-ANALYSIS OF NITROGEN REMOVAL IN RIPARIAN BUFFERS. JOURNAL OF ENVIRONMENTAL QUALITY. American Society of Agronomy, MADISON, WI, 36(4):1172-1180, (2007).
To inform the Public
Riparian buffer zones, the vegetated region adjacent to streams and wetlands, are thought to be effective at intercepting and controlling nitrogen loads entering water bodies. Riparian buffer width may be positively related to nitrogen removal effectiveness by influencing nitrogen retention or removal. We surveyed the scientific literature containing data on riparian buffers and nitrogen concentration in streams and groundwater to identify trends between nitrogen removal effectiveness and buffer width, hydrological flow path, and vegetative cover. Nitrogen removal effectiveness varied widely. Wide buffers (>50 m) more consistently removed significant portions of nitrogen entering a riparian zone than narrow buffers (<15 m). Buffers of various vegetation types were equally effective at removing nitrogen but buffers composed of herbaceous and forest/herbaceous vegetation were more effective when wider. Subsurface removal of nitrogen was efficient, but did not appear to be related to buffer width, while surface removal of nitrogen was partly related to buffer width. Overall quantities of nitrate nitrogen removed per unit length of buffer did not differ by flow path or buffer vegetation type. The general lack of consistent vegetation-type or buffer-width effects on nitrogen removal suggests that soil type, subsurface hydrology (e.g., soil saturation, groundwater flow paths, etc.), and subsurface biogeochemistry (organic carbon supply, nitrate inputs) may play a more important role in determining buffer effectiveness by influencing nitrogen removal through denitrification.
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