Nutrient dynamics in an agricultural watershed: Observations on the role of a riparian forest
TL;DR: Nutrient removals in the riparian forest are thought to be of ecological significance to receiving waters and indicate that coupling natural systems and managed habitats within a watershed may reduce diffuse-source pollution.
Abstract: Nutrient (C, N, and P) concentration changes were measured in surface runoff and shallow groundwater as they moved through a small agricultural (cropland) watershed located in Maryland. During the study period (March 1981 to March 1982), dramatic changes in water-borne nutrient loads occurred in the riparian forest of the watershed. From surface runoff waters that had transited : 50 m of riparian forest, an estimated 4.1 Mg of particulates, 1I kg of particulate organic-N, 0.83 kg of ammonium-N, 2.7 kg of nitrate-N and 3.0 kg of total particulate-P per ha of riparian forest were removed during the study year. In addition, an estimated removal of 45 kg ha- yr-t of nitrate- N occurred in subsurface flow as it moved through the riparian zone. Nutrient uptake rates for the cropland and riparian forest were estimated. These systems were then compared with respect to their pathways of nutrient flow and ability to retain nutrients. The cropland appeared to retain fewer nutrients than the riparian forest and is thought to incur the majority of its nutrient losses in harvested crop. The dominant pathway of total-N loss from the riparian forest seemed to be subsurface flux. Total phosphorus loss from the riparian forest appeared almost evenly divided between surface and subsurface losses. Nutrient removals in the riparian forest are thought to be of ecological significance to receiving waters and indicate that coupling natural systems and managed habitats within a watershed may reduce diffuse-source pollution.
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TL;DR: In this paper, the authors focus on the characterization of landscape patterns and their effects on ecological processes and demonstrate that a long history of ecological studies provides a basis for the study of spatial patterns and landscape-level processes.
Abstract: Consideration of spatial dynamics in many areas of ecology has received increased attention during the past decade. For example, the role of disturbance in creating and maintaining a spatial mosaic in the rocky intertidal zone was studied. Patch size could be predicted very well by using a model based on past patterns of disturbance and on measured patterns of mussel movement and recruitment. The dynamics of many natural disturbances and their effects on the spatial mosaic have received considerable study in a variety of terrestrial and aquatic systems. This paper demonstrates that a long history of ecological studies provides a basis for the study of spatial patterns and landscape-level processes. However, the emphasis previously was on describing the processes that created the patterns observed in the biota. The explicit effects of spatial patterns on ecological processes have not been well studied; the emphasis on pattern and process is what differentiates landscape ecology from other ecological disciplines. Therefore, this review focuses on the characterization of landscape patterns and their effects on ecological processes.
3,065 citations
TL;DR: Riparian zones possess an unusually diverse array of species and environmental processes as discussed by the authors, related to variable flood regimes, geographically unique channel processes, altitudinal climate shifts, and upland influences on the fluvial corridor.
Abstract: Riparian zones possess an unusually diverse array of species and environmental processes. The ecological diversity is related to variable flood regimes, geographically unique channel processes, altitudinal climate shifts, and upland influences on the fluvial corridor. The resulting dynamic environment supports a variety of life-history strategies, biogeochemical cycles and rates, and organisms adapted to disturbance regimes over broad spatial and temporal scales. Innovations in riparian zone management have been effective in ameliorating many ecological issues related to land use and environmental quality. Riparian zones play essential roles in water and landscape planning, in restoration of aquatic systems, and in catalyzing institutional and societal cooperation for these efforts.
2,502 citations
Cites background from "Nutrient dynamics in an agricultura..."
...These investigations quickly led to a new understanding of the role played by riparian zones in controlling nonpoint sources of pollution by sediment and nutrients in agricultural watersheds (Lowrance et al. 1983, Peterjohn and Correll 1984, Jacobs and Gilliam 1985)....
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...…et al. 1995) "the important role of riparian forests in maintaining environmental quality in streams and rivers was the result of investigations into the fate of fertilizer placed on agricultural fields (Peterjohn and Correll 1984) and studies of the effects of logging (Gregory et al. 1991)"....
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...Plant uptake is an important mechanism for nutrient removal in riparian forests (Peterjohn & Correll 1984, Fail et al. 1986, Correll & Weller 1989, Groffman et al. 1992)....
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TL;DR: A conceptual model of riparian tones is proposed that integrates the physical processes that shape valleyfloor landscapes, the succession of terrestrial plant communities on these geomorphic surfaces, the formation of habitat, and the production of nutritional resources for aquatic ecosys-.
Abstract: R iparian zones are the interfaces between terrestrial and aquatic ecosystems. As ecotones, they encompass sharp gradients of environmental factors, ecological processes, and plant communities. Riparian zones are not easily delineated but are comprised of mosaics of landforms, communities, and environments within the larger landscape. We propose a conceptual model of riparian tones that integrates the physical processes that shape valleyfloor landscapes, the succession of terrestrial plant communities on these geomorphic surfaces, the formation of habitat, and the production of nutritional resources for aquatic ecosys-
2,097 citations
Cites background from "Nutrient dynamics in an agricultura..."
...Riparian forests were found to be responsiblc for removal of more nitrate transported from croplands into a Maryland river (Peterjohn and Correll 1984)....
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Florida International University1, State University of New York System2, University of Wisconsin-Madison3, University of California, Santa Barbara4, Arizona State University5, Northern Arizona University6, United States Geological Survey7, University of Minnesota8, University of Washington9, University of New Hampshire10
TL;DR: In this paper, the authors define biogeochemical hot spots as patches that show disproportionately high reaction rates relative to the surrounding matrix, whereas hot moments occur when episodic hydrological flowpaths reactivate and/or mobilize accumulated reactants.
Abstract: Rates and reactions of biogeochemical processes vary in space and time to produce both hot spots and hot moments of elemental cycling. We define biogeochemical hot spots as patches that show disproportionately high reaction rates relative to the surrounding matrix, whereas hot moments are defined as short periods of time that exhibit disproportionately high reaction rates relative to longer intervening time periods. As has been appreciated by ecologists for decades, hot spot and hot moment activity is often enhanced at terrestrial-aquatic interfaces. Using examples from the carbon (C) and nitrogen (N) cycles, we show that hot spots occur where hydrological flowpaths converge with substrates or other flowpaths containing complementary or missing reactants. Hot moments occur when episodic hydrological flowpaths reactivate and/or mobilize accumulated reactants. By focusing on the delivery of specific missing reactants via hydrologic flowpaths, we can forge a better mechanistic understanding of the factors that create hot spots and hot moments. Such a mechanistic understanding is necessary so that biogeochemical hot spots can be identified at broader spatiotemporal scales and factored into quantitative models. We specifically recommend that resource managers incorporate both natural and artificially created biogeochemical hot spots into their plans for water quality management. Finally, we emphasize the needs for further research to assess the potential importance of hot spot and hot moment phenomena in the cycling of different bioactive elements, improve our ability to predict their occurrence, assess their importance in landscape biogeochemistry, and evaluate their utility as tools for resource management.
2,096 citations
Cornell University1, Université libre de Bruxelles2, United States Environmental Protection Agency3, Oregon State University4, Iowa State University5, Stockholm University6, Smithsonian Institution7, Wageningen University and Research Centre8, Commonwealth Scientific and Industrial Research Organisation9, United States Geological Survey10
TL;DR: In this paper, the authors present estimates of total nitrogen and total phosphorus fluxes in rivers to the North Atlantic Ocean from 14 regions in North America, South America, Europe, and Africa which collectively comprise the drainage basins to North Atlantic.
Abstract: We present estimates of total nitrogen and total phosphorus fluxes in rivers to the North Atlantic Ocean from 14 regions in North America, South America, Europe, and Africa which collectively comprise the drainage basins to the North Atlantic. The Amazon basin dominates the overall phosphorus flux and has the highest phosphorus flux per area. The total nitrogen flux from the Amazon is also large, contributing 3.3 Tg yr-1 out of a total for the entire North Atlantic region of 13.1 Tg yr-1. On a per area basis, however, the largest nitrogen fluxes are found in the highly disturbed watersheds around the North Sea, in northwestern Europe, and in the northeastern U.S., all of which have riverine nitrogen fluxes greater than 1,000 kg N km-2 yr-1.
1,614 citations
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TL;DR: Alkalinity measurements are used in the interpretation and control of water and wastewater treatment processes and can be interpreted in terms of specific substances only when the chemical composition of the sample is known.
Abstract: 1. Discussion Alkalinity of a water is its acid-neutralizing capacity. It is the sum of all the titratable bases. The measured value may vary significantly with the end-point pH used. Alkalinity is a measure of an aggregate property of water and can be interpreted in terms of specific substances only when the chemical composition of the sample is known. Alkalinity is significant in many uses and treatments of natural waters and wastewaters. Because the alkalinity of many surface waters is primarily a function of carbonate, bicarbonate, and hydroxide content, it is taken as an indication of the concentration of these constitutents. The measured values also may include contributions from borates, phosphates, silicates, or other bases if these are present. Alkalinity in excess of alkaline earth metal concentrations is significant in determining the suitability of a water for irrigation. Alkalinity measurements are used in the interpretation and control of water and wastewater treatment processes. Raw domestic wastewater has an alkalinity less than, or only slightly greater than, that of the water supply. Properly operating anaerobic digesters typically have supernatant alkalinities in the range of 2000 to 4000 mg calcium carbonate (CaCO3)/L. 1
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2,110 citations
01 Jan 1975
TL;DR: This volume deals with the characterization of the biosphere as a whole in terms of productivity and related properties, and consideration of man’s relationship to theBiosphere.
Abstract: Preceding chapters in this volume have dealt with the history of productivity study, methods of measurement, patterns of productivity in different kinds of communities, and some applications in research. Two topics remain: the characterization of the biosphere as a whole in terms of productivity and related properties, and consideration of man’s relationship to the biosphere. The first topic is the focus of the book as a whole, and it is summarized here as well as in Chapters 10 and 13. The second topic is inescapably problematic; we can offer only a viewpoint on it.
442 citations
TL;DR: In this paper, the riparian ecosystem acts as a nutrient sink and reduces the concentrations and loads of nutrients in the shallow aquifer before the nutrients reach the stream channel, which is hypothesized to be the case in many agricultural watersheds.
Abstract: Much of the runoff from agricultural fields in the southeastern Coastal Plain is carried to a stream channel system in a shallow phreatic aquifer. This subsurface runoff often passes through a band of riparian forest before becoming streamflow. It is hypothesized that the riparian ecosystem acts as a nutrient sink and reduces the concentrations and loads of nutrients in the shallow aquifer before the nutrients reach the stream channel. Concentrations and loads (kg/m²) of NO₃-N, NH₄-N, organic N, dissolved molybdate-reactive P₁ total P, Ca, Mg, K, Cl, and SO₄-S were measured in shallow phreatic wells at 37 locations on an agricultural watershed near Tifton, Ga. Total water volume moving off the watershed in subsurface flow was < 1% of streamflow with corresponding small amounts of nutrients. Nitrate-N, Ca, and Mg had significantly higher concentrations in field wells than in forest or streamside wells. Concentrations of Cl were not reduced as water moved from field to forest. Processes within the riparian zone apparently converted primarily inorganic N from fields (76% NO₃-N, 6% NH₄-N, 18% organic N) into primarily organic N in streamside wells (10% NO₃-N, 14% NH₄-N, and 76% organic N). Concentration differences between field and forest wells indicated the riparian forest's ability to act as a sink for NO₃-N, Ca, Mg, K, and SO₄-S. Due to their role as nutrient sinks, riparian forests are important in maintaining stream water quality on agricultural watersheds.
188 citations