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Christopher M Lorion - One of the best experts on this subject based on the ideXlab platform.
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Riparian Forest buffers mitigate the effects of deForestation on fish assemblages in tropical headwater streams
Ecological Applications, 2009Co-Authors: Christopher M Lorion, Brian P KennedyAbstract:Riparian Forest buffers may play a critical role in moderating the impacts of deForestation on tropical stream ecosystems, but very few studies have examined the ecological effects of Riparian buffers in the tropics. To test the hypothesis that Riparian Forest buffers can reduce the impacts of deForestation on tropical stream biota, we sampled fish assemblages in lowland headwater streams in southeastern Costa Rica representing three different treatments: (1) Forested reference stream reaches, (2) stream reaches adjacent to pasture with a Riparian Forest buffer averaging at least 15 m in width on each bank, and (3) stream reaches adjacent to pasture without a Riparian Forest buffer. Land cover upstream from the study reaches was dominated by Forest at all of the sites, allowing us to isolate the reach-scale effects of the three study treatments. Fish density was significantly higher in pasture reaches than in Forest and Forest buffer reaches, mostly due to an increase in herbivore-detritivores, but fish b...
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Riparian Forest buffers mitigate the effects of deForestation on fish assemblages in tropical headwater streams
Ecological Applications, 2009Co-Authors: Christopher M Lorion, Brian P KennedyAbstract:Riparian Forest buffers may play a critical role in moderating the impacts of deForestation on tropical stream ecosystems, but very few studies have examined the ecological effects of Riparian buffers in the tropics. To test the hypothesis that Riparian Forest buffers can reduce the impacts of deForestation on tropical stream biota, we sampled fish assemblages in lowland headwater streams in southeastern Costa Rica representing three different treatments: (1) Forested reference stream reaches, (2) stream reaches adjacent to pasture with a Riparian Forest buffer averaging at least 15 m in width on each bank, and (3) stream reaches adjacent to pasture without a Riparian Forest buffer. Land cover upstream from the study reaches was dominated by Forest at all of the sites, allowing us to isolate the reach-scale effects of the three study treatments. Fish density was significantly higher in pasture reaches than in Forest and Forest buffer reaches, mostly due to an increase in herbivore-detritivores, but fish biomass did not differ among reach types. Fish species richness was also higher in pasture reaches than in Forested reference reaches, while Forest buffer reaches were intermediate. Overall, the taxonomic and trophic structure of fish assemblages in Forest and Forest buffer reaches was very similar, while assemblages in pasture reaches were quite distinct. These patterns were persistent across three sampling periods during our 15-month study. Differences in stream ecosystem conditions between pasture reaches and Forested sites, including higher stream temperatures, reduced fruit and seed inputs, and a trend toward increased periphyton abundance, appeared to favor fish species normally found in larger streams and facilitate a native invasion process. Forest buffer reaches, in contrast, had stream temperatures and allochthonous inputs more similar to Forested streams. Our results illustrate the importance of Riparian areas to stream ecosystem integrity in the tropics and provide support for Costa Rican legislation protecting Riparian Forests.
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relationships between deForestation Riparian Forest buffers and benthic macroinvertebrates in neotropical headwater streams
Freshwater Biology, 2009Co-Authors: Christopher M Lorion, Brian P KennedyAbstract:SUMMARY 1. Few studies have evaluated the effectiveness of Riparian buffers in the tropics, despite their potential to reduce the impacts of deForestation on stream communities. We examined macroinvertebrate assemblages and stream habitat characteristics in small lowland streams in southeastern Costa Rica to assess the impacts of deForestation on benthic communities and the influence of Riparian Forest buffers on these effects. Three different stream reach types were compared in the study: (i) Forested reference reaches, (ii) stream reaches adjacent to pasture with a Riparian Forest buffer at least 15 m in width on both banks and (iii) stream reaches adjacent to pasture without a Riparian Forest buffer. 2. Comparisons between Forest and pasture reaches suggest that deForestation, even at a very local scale, can alter the taxonomic composition of benthic macroinvertebrate assemblages, reduce macroinvertebrate diversity and eliminate the most sensitive taxa. The presence of a Riparian Forest buffer appeared to significantly reduce the effects of deForestation on benthic communities, as macroinvertebrate diversity and assemblage structure in Forest buffer reaches were generally very similar to those in Forested reference reaches. One Forest buffer reach was clearly an exception to this pattern, despite the presence of a wide Riparian buffer. 3. The taxonomic structure of macroinvertebrate assemblages differed between pool and riffle habitats, but contrasts among the three reach types in our study were consistent across the two habitats. Differences among reach types also persisted across three sampling periods during our 15-month study. 4. Among the environmental variables we measured, only stream water temperature varied significantly among reach types, but trends in periphyton abundance and stream sedimentation may have contributed to observed differences in macroinvertebrate assemblage structure. 5. Forest cover was high in all of our study catchments, and more research is needed to determine whether Riparian Forest buffers will sustain similar functions in more extensively deForested landscapes. Nevertheless, our results provide support for Costa Rican regulations protecting Riparian Forests and suggest that proper Riparian management could significantly reduce the impacts of deForestation on benthic communities in tropical streams.
Brian P Kennedy - One of the best experts on this subject based on the ideXlab platform.
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Riparian Forest buffers mitigate the effects of deForestation on fish assemblages in tropical headwater streams
Ecological Applications, 2009Co-Authors: Christopher M Lorion, Brian P KennedyAbstract:Riparian Forest buffers may play a critical role in moderating the impacts of deForestation on tropical stream ecosystems, but very few studies have examined the ecological effects of Riparian buffers in the tropics. To test the hypothesis that Riparian Forest buffers can reduce the impacts of deForestation on tropical stream biota, we sampled fish assemblages in lowland headwater streams in southeastern Costa Rica representing three different treatments: (1) Forested reference stream reaches, (2) stream reaches adjacent to pasture with a Riparian Forest buffer averaging at least 15 m in width on each bank, and (3) stream reaches adjacent to pasture without a Riparian Forest buffer. Land cover upstream from the study reaches was dominated by Forest at all of the sites, allowing us to isolate the reach-scale effects of the three study treatments. Fish density was significantly higher in pasture reaches than in Forest and Forest buffer reaches, mostly due to an increase in herbivore-detritivores, but fish b...
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Riparian Forest buffers mitigate the effects of deForestation on fish assemblages in tropical headwater streams
Ecological Applications, 2009Co-Authors: Christopher M Lorion, Brian P KennedyAbstract:Riparian Forest buffers may play a critical role in moderating the impacts of deForestation on tropical stream ecosystems, but very few studies have examined the ecological effects of Riparian buffers in the tropics. To test the hypothesis that Riparian Forest buffers can reduce the impacts of deForestation on tropical stream biota, we sampled fish assemblages in lowland headwater streams in southeastern Costa Rica representing three different treatments: (1) Forested reference stream reaches, (2) stream reaches adjacent to pasture with a Riparian Forest buffer averaging at least 15 m in width on each bank, and (3) stream reaches adjacent to pasture without a Riparian Forest buffer. Land cover upstream from the study reaches was dominated by Forest at all of the sites, allowing us to isolate the reach-scale effects of the three study treatments. Fish density was significantly higher in pasture reaches than in Forest and Forest buffer reaches, mostly due to an increase in herbivore-detritivores, but fish biomass did not differ among reach types. Fish species richness was also higher in pasture reaches than in Forested reference reaches, while Forest buffer reaches were intermediate. Overall, the taxonomic and trophic structure of fish assemblages in Forest and Forest buffer reaches was very similar, while assemblages in pasture reaches were quite distinct. These patterns were persistent across three sampling periods during our 15-month study. Differences in stream ecosystem conditions between pasture reaches and Forested sites, including higher stream temperatures, reduced fruit and seed inputs, and a trend toward increased periphyton abundance, appeared to favor fish species normally found in larger streams and facilitate a native invasion process. Forest buffer reaches, in contrast, had stream temperatures and allochthonous inputs more similar to Forested streams. Our results illustrate the importance of Riparian areas to stream ecosystem integrity in the tropics and provide support for Costa Rican legislation protecting Riparian Forests.
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relationships between deForestation Riparian Forest buffers and benthic macroinvertebrates in neotropical headwater streams
Freshwater Biology, 2009Co-Authors: Christopher M Lorion, Brian P KennedyAbstract:SUMMARY 1. Few studies have evaluated the effectiveness of Riparian buffers in the tropics, despite their potential to reduce the impacts of deForestation on stream communities. We examined macroinvertebrate assemblages and stream habitat characteristics in small lowland streams in southeastern Costa Rica to assess the impacts of deForestation on benthic communities and the influence of Riparian Forest buffers on these effects. Three different stream reach types were compared in the study: (i) Forested reference reaches, (ii) stream reaches adjacent to pasture with a Riparian Forest buffer at least 15 m in width on both banks and (iii) stream reaches adjacent to pasture without a Riparian Forest buffer. 2. Comparisons between Forest and pasture reaches suggest that deForestation, even at a very local scale, can alter the taxonomic composition of benthic macroinvertebrate assemblages, reduce macroinvertebrate diversity and eliminate the most sensitive taxa. The presence of a Riparian Forest buffer appeared to significantly reduce the effects of deForestation on benthic communities, as macroinvertebrate diversity and assemblage structure in Forest buffer reaches were generally very similar to those in Forested reference reaches. One Forest buffer reach was clearly an exception to this pattern, despite the presence of a wide Riparian buffer. 3. The taxonomic structure of macroinvertebrate assemblages differed between pool and riffle habitats, but contrasts among the three reach types in our study were consistent across the two habitats. Differences among reach types also persisted across three sampling periods during our 15-month study. 4. Among the environmental variables we measured, only stream water temperature varied significantly among reach types, but trends in periphyton abundance and stream sedimentation may have contributed to observed differences in macroinvertebrate assemblage structure. 5. Forest cover was high in all of our study catchments, and more research is needed to determine whether Riparian Forest buffers will sustain similar functions in more extensively deForested landscapes. Nevertheless, our results provide support for Costa Rican regulations protecting Riparian Forests and suggest that proper Riparian management could significantly reduce the impacts of deForestation on benthic communities in tropical streams.
L. C. Luchini - One of the best experts on this subject based on the ideXlab platform.
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Herbicide distribution in soils of a Riparian Forest and neighboring sugar cane field
Geoderma, 2010Co-Authors: Simone T T Bicalho, Tomaz Langenbach, Ricardo Ribeiro Rodrigues, F.v. Correia, Allen N. Hagler, Marcus Barifouse Matallo, L. C. LuchiniAbstract:Riparian Forests are protected by Brazilian law to preserve rivers and their margins. A sugar cane field adjacent to a strip of young Riparian Forest bordering an older Riparian Forest along a stream was used to study the Riparian Forest as a buffer zone to prevent pesticides pollution. Concentrations of the herbicides diuron, hexazinone and tebuthiuron were determined in different soil layers of a Red Yellow Oxisol during 2003 and 2004. The determination was done by High Performance Liquid Chromatography with reverse phase C-18 column, through two mobile phases. Diuron and hexazinone concentration diminished between the sugar cane and Riparian Forest as buffer strip demonstrating a protective effect. However, tebuthiuron had about four times higher concentrations in the old Riparian Forest compared to the other areas. Concentrations were higher in the surface and decreased in deeper soil layers in the old Riparian Forest suggesting that this herbicide probably was introduced by air pollution. This pesticide concentrated in the canopy could be washed by rain to the soil adjacent to the stream. Our data suggest that climate conditions were responsible for enhanced volatilization exposing the old Riparian Forest to more air pollution that was captured by the higher canopy.
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Herbicide distribution in soils of a Riparian Forest and neighboring sugar cane field
Geoderma, 2010Co-Authors: Simone T T Bicalho, Tomaz Langenbach, Ricardo Ribeiro Rodrigues, F.v. Correia, Allen N. Hagler, Marcus Barifouse Matallo, L. C. LuchiniAbstract:Riparian Forests are protected by Brazilian law to preserve rivers and their margins. A sugar cane field adjacent to a strip of young Riparian Forest bordering an older Riparian Forest along a stream was used to study the Riparian Forest as a buffer zone to prevent pesticides pollution. Concentrations of the herbicides diuron, hexazinone and tebuthiuron were determined in different soil layers of a Red Yellow Oxisol during 2003 and 2004. The determination was done by High Performance Liquid Chromatography with reverse phase C-18 column, through two mobile phases. Diuron and hexazinone concentration diminished between the sugar cane and Riparian Forest as buffer strip demonstrating a protective effect. However, tebuthiuron had about four times higher concentrations in the old Riparian Forest compared to the other areas. Concentrations were higher in the surface and decreased in deeper soil layers in the old Riparian Forest suggesting that this herbicide probably was introduced by air pollution. This pesticide concentrated in the canopy could be washed by rain to the soil adjacent to the stream. Our data suggest that climate conditions were responsible for enhanced volatilization exposing the old Riparian Forest to more air pollution that was captured by the higher canopy. (C) 2010 Elsevier B.V. All rights reserved.CNPqFAPERJPRONEX-CNPqCAPE
Simone T T Bicalho - One of the best experts on this subject based on the ideXlab platform.
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the fate of tebuthiuron in microcosm with Riparian Forest seedlings
Geoderma, 2013Co-Authors: Simone T T Bicalho, Tomaz LangenbachAbstract:Abstract This work studies the fate of tebuthiuron in the presence of the Riparian Forest species Cecropia hololeuca Miq. and Trema micranta (L) Blum. Seedlings of these species were cultivated in microcosms with additions of 14 C-tebuthiuron in order to trace the molecules of this herbicide using a simulated ground water upstream movement from the bottom layers to the upper soil layers. The C. hololeuca survive rate was very high with an uptake of 45 ± 5% differently from T. micrantha that had a low survival rate with an uptake of only 20 ± 7%. The first leaves of C. hololeuca that fell showed high radioactivity while the leaves that fell towards the end of the experiment had a strong decrease that could suggest a detoxification mechanism by discarding the pollutant via leaf fall. After 78 days of incubation, the mineralization of 14 C-tebuthiuron was no more than 0.9% of the applied amount in both species. This low value plus the lack of metabolite data of this molecule suggests that this compound is not easily biodegradable and therefore is highly persistent in the environment.
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Distribution of the herbicide atrazine in a microcosm with Riparian Forest plants.
Journal of environmental science and health. Part. B Pesticides food contaminants and agricultural wastes, 2012Co-Authors: Simone T T Bicalho, Tomaz LangenbachAbstract:Pesticides applied on sugarcane reach the subsoil of Riparian Forests and probably contaminate the river water. This work was conducted to learn about the phytoremediation of atrazine and subsoil contamination using the common Riparian Forest species of Cecropia hololeuca Miq. and Trema micranta (L.) Blum. These plants were grown in soil microcosms where 14C-atrazine at 1/10 of the field-recommended dose was applied at the bottom of the microcosm simulating the movement from contaminated ground water to the upper soil layers and into plants. Residues of 14C-atrazine were detected in all parts of the microcosm including soil, rhizosphere and the roots in different layers of the microcosm, stem and leaves. Atrazine mineralization was higher (10.2%) in the microcosms with plants than the control microcosms without plants (1.2%). The upward movement of this pesticide from deeper to more superficial soil layers occurred in all the microcosms with plants, powered by evapotranspiration process. From the atrazine...
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Herbicide distribution in soils of a Riparian Forest and neighboring sugar cane field
Geoderma, 2010Co-Authors: Simone T T Bicalho, Tomaz Langenbach, Ricardo Ribeiro Rodrigues, F.v. Correia, Allen N. Hagler, Marcus Barifouse Matallo, L. C. LuchiniAbstract:Riparian Forests are protected by Brazilian law to preserve rivers and their margins. A sugar cane field adjacent to a strip of young Riparian Forest bordering an older Riparian Forest along a stream was used to study the Riparian Forest as a buffer zone to prevent pesticides pollution. Concentrations of the herbicides diuron, hexazinone and tebuthiuron were determined in different soil layers of a Red Yellow Oxisol during 2003 and 2004. The determination was done by High Performance Liquid Chromatography with reverse phase C-18 column, through two mobile phases. Diuron and hexazinone concentration diminished between the sugar cane and Riparian Forest as buffer strip demonstrating a protective effect. However, tebuthiuron had about four times higher concentrations in the old Riparian Forest compared to the other areas. Concentrations were higher in the surface and decreased in deeper soil layers in the old Riparian Forest suggesting that this herbicide probably was introduced by air pollution. This pesticide concentrated in the canopy could be washed by rain to the soil adjacent to the stream. Our data suggest that climate conditions were responsible for enhanced volatilization exposing the old Riparian Forest to more air pollution that was captured by the higher canopy.
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Herbicide distribution in soils of a Riparian Forest and neighboring sugar cane field
Geoderma, 2010Co-Authors: Simone T T Bicalho, Tomaz Langenbach, Ricardo Ribeiro Rodrigues, F.v. Correia, Allen N. Hagler, Marcus Barifouse Matallo, L. C. LuchiniAbstract:Riparian Forests are protected by Brazilian law to preserve rivers and their margins. A sugar cane field adjacent to a strip of young Riparian Forest bordering an older Riparian Forest along a stream was used to study the Riparian Forest as a buffer zone to prevent pesticides pollution. Concentrations of the herbicides diuron, hexazinone and tebuthiuron were determined in different soil layers of a Red Yellow Oxisol during 2003 and 2004. The determination was done by High Performance Liquid Chromatography with reverse phase C-18 column, through two mobile phases. Diuron and hexazinone concentration diminished between the sugar cane and Riparian Forest as buffer strip demonstrating a protective effect. However, tebuthiuron had about four times higher concentrations in the old Riparian Forest compared to the other areas. Concentrations were higher in the surface and decreased in deeper soil layers in the old Riparian Forest suggesting that this herbicide probably was introduced by air pollution. This pesticide concentrated in the canopy could be washed by rain to the soil adjacent to the stream. Our data suggest that climate conditions were responsible for enhanced volatilization exposing the old Riparian Forest to more air pollution that was captured by the higher canopy. (C) 2010 Elsevier B.V. All rights reserved.CNPqFAPERJPRONEX-CNPqCAPE
Richard Lowrance - One of the best experts on this subject based on the ideXlab platform.
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Watershed-Scale Water Quality Impacts of Riparian Forest Management
Journal of Water Resources Planning and Management, 1999Co-Authors: Calvin D. Perry, Richard Lowrance, George Vellidis, D. L. ThomasAbstract:The SPANS (SPatial ANalysis System) Geographic Information System (GIS) and the Georgia Landcover Database were used to identify land use within the 333 km2 Little River Research Watershed of Georgia and to perform a variety of spatial analyses with the purpose of determining the water quality impact of Riparian Forest management within the watershed. The watershed contains a dense dendritic stream network, with approximately 54% of a 30 m Riparian buffer on either side of all streams of second order or larger currently in Forest cover. Approximately 60% of the upland is in some type of agricultural production. GIS analyses were used to extrapolate field-scale measurements on Riparian Forest nonpoint-source-pollution nutrient buffering capacity to the watershed-scale, and to evaluate the water quality impact of three increasing deForestation and three increasing reForestation Riparian Forest management scenarios. Nitrogen (N) and phosphorus (P) loadings at the watershed outlet could potentially increase b...
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Management effects on runoff and sediment transport in Riparian Forest buffers
Transactions of the ASAE, 1999Co-Authors: Joseph M. Sheridan, Richard Lowrance, David D. BoschAbstract:The effectiveness of mature Riparian Forests in reducing the impact of agriculture on the quality of the nation’s water resources has been documented, but the impact of Forest management practices implemented within Riparian Forest buffers on their water quality function has not been evaluated. This article examines the effect of Forest management within a Coastal Plain Riparian Forest buffer system (RFBS) on runoff and sediment transport over a four year period. The RFBS, which conformed to USDA-FS and USDA-NRCS best management recommendations, included a narrow strip of undisturbed Forest located adjacent to the stream drainage system (Zone 1), a wide managed pine Forest downslope from the grass filter (Zone 2), and a narrow grass filter strip immediately downslope from an agricultural field (Zone 3). Forest management treatments evaluated within Zone 2 were mature Forest, clear-cut, and selectively-thinned. Significant reductions in runoff and sediment transport were measured under all three Forest management treatments. The primary zone of runoff and sediment reduction was within the grass filter portion of the RFBS. These results indicate that Riparian Forests within a RFBS may be managed for economic return to the land owner without adversely affecting the runoff and sediment reduction function performed by these buffer systems.
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water quality functions of Riparian Forest buffers in chesapeake bay watersheds
Environmental Management, 1997Co-Authors: Richard Lowrance, Peter M. Groffman, L S Altier, J D Newbold, R R Schnabel, J M Denver, D L Correll, J W Gilliam, J L Robinson, R B BrinsfieldAbstract:/ Maryland, Virginia, and Pennsylvania, USA, have agreed to reduce nutrient loadings to Chesapeake Bay by 40% by the year 2000. This requires control of nonpoint sources of nutrients, much of which comes from agriculture. Riparian Forest buffer systems (RFBS) provide effective control of nonpoint source (NPS) pollution in some types of agricultural watersheds. Control of NPS pollution is dependent on the type of pollutant and the hydrologic connection between pollution sources, the RFBS, and the stream. Water quality improvements are most likely in areas of where most of the excess precipitation moves across, in, or near the root zone of the RFBS. In areas such as the Inner Coastal Plain and Piedmont watersheds with thin soils, RFBS should retain 50%-90% of the total loading of nitrate in shallow groundwater, sediment in surface runoff, and total N in both surface runoff and groundwater. Retention of phosphorus is generally much less. In regions with deeper soils and/or greater regional groundwater recharge (such as parts of the Piedmont and the Valley and Ridge), RFBS water quality improvements are probably much less. The expected levels of pollutant control by RFBS are identified for each of nine physiographic provinces of the Chesapeake Bay Watershed. Issues related to of establishment, sustainability, and management are also discussed.KEY WORDS: Riparian Forest buffers; Chesapeake Bay; Nonpoint source pollution; Nitrogen; Phosphorus; Sediment
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Solute Transport and Filtering Through a Riparian Forest
Transactions of the ASAE, 1996Co-Authors: Robert K. Hubbard, Richard LowranceAbstract:A two and a half year study was conducted to determine the fate of solutes applied to the landscape position just above the upper edge of a Forested Riparian zone. Nitrate (NO3-N) and bromide (Br) sources were applied to an 18 ¥ 18 m killed grass sod area at the rates of 188 and 336 kg ha–1 N and Br, respectively. Soil samples were collected four times during the study to determine vertical and lateral transport within the treatment area. Shallow groundwater wells were installed at transect positions 13 and 6 m upslope, and 2, 7, 12, 17, and 22 m downslope from the grass sod-Riparian Forest interface. There were two sets of wells at each transect position in the treatment area, and three sets of wells at each transect position in the Forested Riparian zone. The well depths for each set were 0.5, 1.0, 1.5, and 2.0 m. Water samples were collected biweekly except for the final six months of the study, when they were collected monthly. Water samples were analyzed for NO3-N and Br content. Mass balance calculations based on soil sample analyses showed that the equivalent of 59 and 78% of the applied NO3-N and Br had left the treatment area after one year. High NO3-N concentrations observed in well waters in the upslope end of the treatment area showed that shallow groundwater entering from upslope was carrying NO3-N in addition to that applied. Comparisons of Br and NO3-N concentrations in the wells and also Br/NO3-N ratios showed that the Riparian Forest was effectively filtering NO3-N entering from the treatment area. Very little NO3-N was observed in wells 7 and 12 m into the Forest. Bromide concentrations observed in the wells were relatively high at 2, 7, and 12 m into the Forest. Mean Br/NO3-N ratios showed that some Br had reached as far downslope as 22 m into the Riparian Forest by the end of the second year of the study. One pulse of Br appeared in the Riparian Forest 8 to 11 months after application and a second pulse with greater concentrations appeared 16 to 18 months after application. The first pulse is believed to be due to transport via macropore flow, while the second may have been associated with Br initially retained in the soil matrix. Overall the study showed that in areas of the Coastal Plain where shallow lateral water movement is a dominant loss pathway, agrichemicals applied in the spring move downslope during the wet months, and depending on soil type, may take several seasons before completely leaving the upslope area and moving into or through the Riparian Forest.
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Denitrification in a Restored Riparian Forest Wetland
Journal of Environmental Quality, 1995Co-Authors: Richard Lowrance, George Vellidis, Robert K. HubbardAbstract:Groundwater nitrate moving from upland areas toward streams can be removed by denitrification in mature Riparian Forests, but denitrification in restored Riparian Forests has not been quantified. We determined denitrification rates in a restored Riparian wetland below a liquid manure application site. A Riparian Forest buffer consisting of hardwoods along the stream and pines above the hardwoods was established according to USDA specifications. Denitrification was measured monthly using the acetylene inhibition technique on intact soil cores for 2 mo before manure application began and for 24 mo after manure application. Groundwater movement of NO 3 - -N and total Kjeldahl N were estimated biweekly. Average annual denitrification rate was 68 kg N 2 O-N ha -1 yr -1 . Denitrification was significantly higher in a grassed area than in either of the Forested areas. Denitrification did not differ significantly between the hardwood and pine areas. Denitrification was greater than a conservative estimate of groundwater input of total N. Denitrification rates were higher in April and May 1992 and 1993, after manure application to the upland began, compared with April and May 1991, before manure application began. These results indicate that a Riparian wetland, which has not undergone hydrologic modifications, can have denitrification rates comparable to mature Riparian Forests. Higher denitrification rates in an adjacent grassed wetland and lack of differences in denitrification in hardwood and pine zones indicates that the high denitrification rates were due to factors other than the reForestation itself. Compared with groundwater inputs of N, denitrification was an important sink for N moving from the upland management system.
