About this Research Topic
Transport of sediment, nutrients, and other pollutants from cropland to streams and associated water quality degradation is a global concern. Mitigating nutrient losses from cropland requires multiple best management practices aimed at minimizing nutrient sources and transport. Riparian buffers are considered biogeochemical hot spots and promoted to reduce nutrient transport risk to streams. However, buffer efficacy depends on site-specific hydrology, soils, vegetation, buffer width, seasonality and other factors. Buffers can act as both a source and sink for nitrogen (N) and phosphorus (P) depending on biogeochemical dynamics, hydrology and the temporal/spatial scale of interest. Nutrient attenuation trade-offs also occur in buffers and require further study. Soil characteristics that promote denitrification (i.e., poor drainage, abundant organic carbon) may increase the risk of dissolved P release from soils and N losses to the atmosphere. In addition, substantial P loads to streams can occur via stream bank erosion, thus offsetting P removed by buffers from cropland runoff. Certain agricultural practices may also overwhelm buffer attenuation processes. Accurately predicting nutrient attenuation in buffers is difficult. Research has clearly shown that hydrogeochemical factors strongly impact N retention in buffers, however P biogeochemistry in buffers is not as well understood. Soil P attenuation processes vary depending on hydrologic flow path, soil P saturation, redox conditions, mineralogy, seasonality, adjacent cropland practices and other factors. It is clear that inorganic P status of buffers is important, however organic P may also contribute to P fluxes in surface runoff and subsurface flows. There is a general lack of research on the specific mechanisms controlling P retention in buffers and practical soil indices to better predict P release potential are needed. Nutrient dynamics in restored and re-saturated buffers needs further study, particularly when former croplands are used for buffers. Lower organic carbon and elevated nutrient status in former cropland may reduce effectiveness of restored buffers. While saturated buffers show promise for mitigating nitrate-N, they could elevate P mobilization risk in some settings. More research on the cost and effectiveness of engineered buffers in general is needed. Virtually no research has addressed buffer performance during the winter months in northern climates. Since a large portion of annual runoff occurs during snowmelt, quantifying nutrient attenuation during the winter is imperative for improved buffer management and water quality. We invite manuscripts that address riparian buffer nutrient dynamics with the goal of optimizing nonpoint source nutrient attenuation by buffers for improved water quality.
Keywords: Biogeochemistry, riparian zones, nitrogen, phosphorus, nonpoint source water quality
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