Effects of Riparian Buffer Vegetation and Width: A 12‐Year Longitudinal Study

Abstract

Agricultural contributions of nitrogen are a serious concern for many water resources and have spurred the implementation of riparian buffer zones to reduce groundwater nitrate (NO 3 ). The optimum design for buffers is subject to debate, and there are few long-term studies. The objective of this project was to determine the effectiveness over time (12 yr) of buffer types (trees, switchgrass, fescue, native, and a control) and buffer widths (8 and 15 m) by measuring groundwater NO 3 -N and dissolved organic carbon (DOC) trends. At the intermediate groundwater depth (1.5-2.1 m), NO 3 -N reduction effectiveness was 2.5 times greater (46 vs. 16%) for the wider buffer, and, regardless of width, buffer effectiveness increased 0.62% yr -1. Buffer vegetative type was never statistically significant. In the deep-groundwater depth (2.1-3.5 m), there was no change in NO 3 -N removal over time, although the statistical interaction of width and vegetative type indicated a wide range of removal rates (19-82%). The DOC concentrations were analyzed at the field/buffer and buffer/ stream sampling locations. Depending on location position and groundwater sampling depth, DOC concentrations ranged from 1.6 to 2.8 mg L -1 at Year 0 and increased at a rate of 0.13 to 0.18 mg L -1 yr -1 but always remained low (≤5.0 mg L -1). Greater DOC concentrations in the intermediate-depth groundwater did not increase NO 3 -N removal; redox measurements indicated intermittent reduced soil conditions may have been limiting. This study suggests that riparian buffer width, not vegetation, is more important for NO 3 -N removal in the middle coastal plain of North Carolina for a newly established buffer.

Stoichiometric constraints on the microbial processing of carbon with soil depth along a riparian hillslope

“…Areas adjacent to watercourse are assumed to play a key role in C dynamics mainly due to the influence of hydrologic regimes and riparian vegetation which: 1) controls import/export OM fluxes between the watercourse and the floodplain, 2) creates fluctuations of anaerobic/aerobic conditions regulating C source/sink balance, and 3) encourages more diverse microbial communities (Camino-Serrano et al 2016; Gurtz et al 1988; King et al 2016; Lewis et al 2003). However, as far as soil physicochemical properties are concerned, our results disagree with the general assumption of more potential for C storage within the riparian zone.…”

Evaluating riparian solutions to multiple stressor problems in river ecosystems — A conceptual study

“…5). Buffer width was positively related to N and P retention (Dosskey, 2001;Feld et al, 2011;Sweeney & Newbold, 2014;King et al, 2016) and, together with buffer zonation, they can control the amount of nutrients retained from surface runoff and upper groundwater…”

“…A buffer width of 30 m was reported to effectively retain N and P from surface and sub-surface groundwater runoff, if buffers consisted of multiple zones of mature wooded vegetation and grass strips (Feld et al, 2011;Sweeney & Newbold 2014). King et al (2016) found that 15 m wide buffers retained 2.5 times more nitrogen from the sub-surface groundwater than 8 m wide buffers, while buffer vegetation type had no significant effect.…”

Flood Risk Reduction from Agricultural Best Management Practices

“…Previous studies have largely focused on assessment of BMP performance in reducing nutrient and sediment loss and the subsequent impacts on water quality (Parajuli et al 2013;Weissteiner et al 2013;Kladivko et al 2014;Yeo et al 2014;McLellan et al 2015;King et al 2016;Merriman et al 2018) (see also study reviews in Hashemi et al 2016;Liu et al 2017). Previous studies have largely focused on assessment of BMP performance in reducing nutrient and sediment loss and the subsequent impacts on water quality (Parajuli et al 2013;Weissteiner et al 2013;Kladivko et al 2014;Yeo et al 2014;McLellan et al 2015;King et al 2016;Merriman et al 2018) (see also study reviews in Hashemi et al 2016;Liu et al 2017).…”

“…Assessing benefits of agricultural BMPs is challenging due to the multiple impacts on hydrology, nutrient cycling, soil fertility, and other processes. Previous studies have largely focused on assessment of BMP performance in reducing nutrient and sediment loss and the subsequent impacts on water quality (Parajuli et al 2013;Weissteiner et al 2013;Kladivko et al 2014;Yeo et al 2014;McLellan et al 2015;King et al 2016;Merriman et al 2018) (see also study reviews in Hashemi et al 2016;Liu et al 2017). BMPs that slow runoff are effective in reducing sediment detachment and transport (Bosch et al 2013;Mitchell et al 2018), although effectiveness can vary depending on watersheds characteristics, BMPs location, and storm magnitude.…”