Download or read book Nitrate Dynamics Within an Agricultural Stream written by David Robert Sheridan and published by . This book was released on 1993 with total page 224 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Nitrate Dynamics and Source Within Nested Watersheds of an Agricultural Stream Nebraska USA written by Galen I. S. Richards and published by . This book was released on 2020 with total page 82 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bazile Creek flows north through Northeast Nebraska, entering the Missouri River just east of Niobrara, NE. The headwaters of the stream lie within the Bazile Groundwater Management Area (BGMA), a 1958 km2 region created in 2016 characterized by nonpointsource groundwater nitrate contamination. Elevated nitrate concentrations have been seen in the management area since the 1980s, and over time groundwater nitrate concentrations have continued to rise and affect an increasing number of wells. The BGMA contains parts of the Lower Niobrara, Lewis and Clark, Upper Elkhorn, and Lower Elkhorn Natural Resources Districts (NRDs). These NRDs have been working together to both monitor groundwater nitrate levels through periodic well sampling and curb increasing groundwater nitrate trends by educating landowners on methods to reduce fertilizer nitrogen loss through leaching and runoff. Although groundwater nitrate sampling in the Bazile Creek watershed has been continuous, surface water nitrate sampling has been infrequent and tributaries to Bazile Creek have never been sampled. Bazile Creek is a strongly gaining stream, indicating that a large percentage of its flow is derived from groundwater discharge. Nitrate concentrations in Bazile Creek have been slowly increasing, and nitrate in discharging groundwater is suspected to be the cause. This has led to questions about nitrate concentrations in Bazile Creek over time as well as throughout the watershed. This includes tributaries to Bazile Creek, which may all have similar nitrate concentrations or could vary between each other significantly. The source of nitrate entering Bazile Creek has not been determined, however it is assumed to be nitrogen containing fertilizers applied to the many agricultural fields nearby. A large quantity of well and excessively drained soils in the area indicate that fertilizer loss through leaching is probable. Livestock are present throughout the Bazile Creek watershed as well, indicating that manure-derived nitrate could also be making its way into the stream. Further complicating determinations on nitrate source is its potential seasonality, with manure-derived nitrate inputs being greatest in the spring and summer when frequent rainstorms create runoff that can transport manure off of fields into streams. This thesis aims to answer questions about nitrate dynamics and source within the headwaters of the Bazile Creek watershed. Surface water nitrate samples were collected over a period of 15 months from five tributaries and three locations on the main channel. Source seasonality was investigated through the collection of seasonal and rain event nitrate isotope samples, which also provided insight on denitrification rates. Results were then compared to subwatershed characteristics such as total area, land use, and soil drainage. Watershed-scale seasonal trends in discharge and precipitation were also investigated. These comparisons allow for conclusions to be made on nitrate source, primary transport pathways, and concentration seasonality.

Download or read book Nitrate Dynamics of Small Agricultural Streams in the Western Corn Belt Plains Ecoregion written by Shih-Hsien Wang and published by . This book was released on 1997 with total page 596 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Dynamics of Nitrate Phosphorus and Suspended Sediment Transport in Two Agricultural Streams in Central Illinois written by Luke W. Lampo and published by . This book was released on 2017 with total page 163 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nutrients such as nitrate and phosphorus are necessary for life, but excessive amounts can be detrimental. Large amounts of nutrients entering bodies of water can lead to hypoxic zones such as the one in the Gulf of Mexico. Nutrients are also problematic in drinking water reservoirs, as high concentrations of nitrate in drinking water can cause health conditions such as blue baby syndrome and high phosphorus concentrations can lead to algal blooms. Suspended sediment leads to reservoir sedimentation, habitat degradation, and is able to transport particulate nutrients. High nutrient and sediment concentrations are a recurring problem in the drinking water reservoirs for the City of Bloomington, Illinois where water is drawn from two reservoirs -- Evergreen Lake and Lake Bloomington. The primary source of these nutrients is from agriculture, which dominates the land use in the area. To better understand the dynamics of nitrate, phosphorus, and suspended sediment transported into these reservoirs, water samples were collected at the major tributary for each reservoir - Six Mile Creek for Evergreen Lake and Money Creek for Lake Bloomington. SedEvent, an autosampler system that uses a turbidity threshold sampling method to determine when a rain event is occurring, was used to collect water samples at both tributaries. Water samples were analyzed for nitrate, total phosphorus, and dissolved reactive phosphorus using flow injection analysis (FIA). Samples were analyzed for suspended sediment by filtration and drying of samples. Results showed high nutrient and suspended sediment concentrations and loads in both creeks during or just after rain events, when discharge was high. Nitrate concentrations ranged from 1.58 to 13.3 ppm, total phosphorus concentrations ranged from 11.9 to 1250 ppb, and total suspended sediment concentrations ranged from 2.5 to 4100 ppm. Seasonal patterns in nutrient dynamics were present and, in general, water quality tended to be lower during the spring and higher during the summer. In both Six Mile and Money Creek, the majority (>70%) of phosphorus and total suspended sediment cumulative load occurred during stormflow conditions which accounted for less than 25% of flow time. The majority of nitrate cumulative load at Six Mile Creek occurred during baseflow conditions and at Money Creek, slightly more nitrate was transported during stormflow. Overall, seasonal changes in water quality coincide with agricultural activities, which suggests that alternative management practices may help improve water quality.

Download or read book Nitrate Sinks and Sources as Controls of Spatio temporal Water Quality Dynamics in an Agricultural Headwater Catchment written by Tobias Schütz and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Nitrate Transformations and Loss in an Agricultural Stream written by Thomas Matthew Isenhart and published by . This book was released on 1988 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Effects of Land Use on Stream Nitrate Concentrations written by Cara J. Poor and published by . This book was released on 2006 with total page 386 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work furthers the understanding of processes occurring in catchments that affect stream nitrate concentrations using two different approaches: a temporally intensive case study of three headwater catchments with varying land use (through storm event monitoring) and a spatially intensive study on the regional scale (through statistical modeling) of 1st-4th order catchments. At the catchment scale, stream nitrate concentrations during three storm events were monitored in three catchments with different land uses (forested, agricultural, residential) to determine how land use affects nitrate "patterns" during storm events. Overall, results of storm event nitrate concentrations suggest that varying nitrate inputs have a large affect on nitrate dynamics. While within-storm nitrate concentration response patterns in the residential catchment were the same as the patterns in the reference forested catchment (a "concentration" pattern throughout the year), a "dilution" pattern was observed in the fall and winter and a "concentration" pattern was observed in the spring in the agricultural catchment. At the regional scale, a statistical model was developed using land use and either topographic index (TI) or hydrologic landscape regions (HLRs) to predict stream nitrate concentrations during lowflow. Including TI and HLRs (in the form of primary hydrologic flowpaths) significantly improved chloride predictions, but did not improve nitrate predictions. Results of the linear regressions imply that the hydrologic setting of the catchments are adequately represented (from chloride, which is tightly linked to hydrology), and nitrate is more strongly affected by processes such as denitrification and plant uptake during lowflow. Agricultural effects were seen both on the smaller catchment scale and the regional scale. Different patterns were observed in the agricultural catchment during storm events, and chloride was elevated in the Willamette Valley where agricultural activity is concentrated. The temporal pattern of nitrate during storm events was found to be largely controlled by the spatial organization of land cover, whereas the spatial pattern of land cover did not control stream nitrate concentrations sufficiently to improve predictions of nitrate during lowflow. Future work should determine whether or not the spatial pattern of land cover, TI, and HLRs improves nitrate predictions during storm events.

Download or read book Riverine Ecosystem Management written by Stefan Schmutz and published by Springer. This book was released on 2018-05-08 with total page 562 pages. Available in PDF, EPUB and Kindle. Book excerpt: This open access book surveys the frontier of scientific river research and provides examples to guide management towards a sustainable future of riverine ecosystems. Principal structures and functions of the biogeosphere of rivers are explained; key threats are identified, and effective solutions for restoration and mitigation are provided. Rivers are among the most threatened ecosystems of the world. They increasingly suffer from pollution, water abstraction, river channelisation and damming. Fundamental knowledge of ecosystem structure and function is necessary to understand how human acitivities interfere with natural processes and which interventions are feasible to rectify this. Modern water legislation strives for sustainable water resource management and protection of important habitats and species. However, decision makers would benefit from more profound understanding of ecosystem degradation processes and of innovative methodologies and tools for efficient mitigation and restoration. The book provides best-practice examples of sustainable river management from on-site studies, European-wide analyses and case studies from other parts of the world. This book will be of interest to researchers in the field of aquatic ecology, river system functioning, conservation and restoration, to postgraduate students, to institutions involved in water management, and to water related industries.

Download or read book A Vision Towards Developing a Spatially And Temporally Robust Data Driven Modeling Framework To Predict Continuous Stream Nitrate Concentration At Data Scarce Locations written by Gourab Saha and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stream nitrate concentration provides critical insights into nutrient dynamics and can help improve the effectiveness of sustainable ecosystem management decisions. Conventional stream nitrate monitoring is conducted through lab analysis using in-situ water samples, typically at coarse temporal resolution. In the United States, federal agencies and a few state and local agencies started collecting high-frequency (5-60 min intervals) nitrate data using optical sensors in the last decade. These sensor-based high-frequency stream nitrate concentrations at multiple stream locations in a region provide valuable information on the dynamics of nitrate transport, including the timing, magnitude, and sources of nitrate loading in the environmental system. This study hypothesized that the nitrate dynamics information available in a region's high-frequency stream nitrate monitoring sites could be used to estimate spatially and temporally continuous nitrate concentration at other low-frequency monitoring locations. Deep learning (DL) models could use to extract the complex nutrient dynamics from the high-frequency sites and transferred the information to low-frequency monitoring sites. The primary goal of this study was to develop a spatially and temporally robust data-driven modeling framework to predict continuous stream nitrate concentration at data-limited sites in a region using high-frequency nitrate data and biophysical attributes of the region. The objectives of this study are to (1) develop a deep learning (DL)-based modeling approach to generate continuous daily stream nitrate concentration for nitrate data-sparse watersheds and compare the performance of the developed modeling approach with other statistical models; (2) analyze the deep learning approach-based modeling framework to understand the critical environmental drivers of predicting daily nitrate concentrations, and; (3) explore the potential of extending the developed modeling framework to stream discharge unavailable locations for making the framework more spatially robust. This study used a DL model called Long Short-Term Memory (LSTM) to estimate continuous daily stream nitrate. The DL model received climate, land use, fertilization, topography, and soil characteristics data as inputs during the model development. The DL model was trained comprehensively by using four hyperparameters (batch size, hidden layer size, time window, and epoch) and isolating the best combination of hyperparameters based on five performance metrics, including RMSE, bias, correlation, NSE, and KGE. The hypothesis was tested with Iowa, USA, as a case study region because the state had more high-frequency nitrate monitoring sites with long-term data. In the first objective, a DL model-based stream nitrate estimation framework was trained and tested for thirty-four (34) high-frequency and eight (8) low-frequency nitrate monitoring sites. DL model demonstrated median test-period Nash-Sutcliffe efficiency (NSE) = 0.75 to estimate continuous daily stream nitrate concentration, which is unprecedented performance. Twenty-one sites (50% of all nitrate monitoring sites) and thirty-four sites (76%) demonstrated NSE greater than 0.75 and 0.50, respectively. The concentration (c) - discharge (Q) relationship analysis showed that the study watersheds had four dominant nitrate transport patterns from landscapes to streams with increasing discharge, including (i) flushing, (ii) flushing during low Q (Q median Q, Q50) and chemostatic during high Q (Q Q50), (iii) flushing during low Q and dilution during high Q and (iv) chemodynamic. The flushing pattern was identified as the most dominant c-Q relationship pattern. The developed DL modeling framework's performance was compared with other widely used statistical models, including Weighted Regressions on Time, Discharge, and Season (WRTDS) and Load Estimator (LOADEST), for the case study region. The study assumed that each basin had only one high-frequency monitoring site within the region. In this study, high-frequency nitrate data from each site were randomly subsampled to biweekly data and used as a pseudo-low-frequency site to train the DL model. These sites' remaining daily nitrate data were used for the developed DL model's performance evaluation. DL and WRTDS models performed similarly in most low-frequency nitrate monitoring sites. However, the developed DL model performed better at a few low-frequency nitrate monitoring sites. The DL and WRTDS models' performance in continuous nitrate estimation was better than the LOADEST model. Though the developed DL model performed exceptionally well in many sites, the performance was low for a few nitrate monitoring sites. The second objective identified the critical environmental drivers that impacted the data-driven modeling approach in estimating continuous stream nitrate concentrations. DL models were developed to predict daily stream nitrate concentrations at locations lacking continuous data. The sensitivity of daily varying environmental variables, including high-frequency nitrate and stream discharge and day length (representing seasonality) data, was identified in estimating continuous nitrate concentrations. The similarity between the sensitive variables was determined using Dynamic Time Warping (DTW) method to assess the contribution of biophysical similarity on the DL model performance. The DL model learned and transferred nitrate dynamics to sites within a radius of 300 km of a high-frequency nitrate monitoring site. The dominant annual c-Q relationship plots inferred that the DL model potentially learned nitrate dynamics from the data of a high-frequency nitrate monitoring site and predicted continuous nitrate concentrations accurately at low-frequency nitrate sites. DTW analysis indicated a similarity in nitrate concentration, stream discharge, and day length between a low-frequency and a high-frequency nitrate monitoring site, contributing to the accurate daily stream nitrate prediction. The third objective aimed to expand the data-driven modeling framework to those stream locations where stream discharge information is unavailable and make the framework more spatially robust. This study evaluated the potential of precipitation or simulated stream discharge data to be used as a surrogate of observed stream discharge data for the data-driven model development. Five cases were developed based on the DL modeling framework using the combination of precipitation, observed, and simulated stream discharge values to identify the most significant variable for estimating stream nitrate concentrations. The DL model, developed with observed stream discharge as a crucial environmental characteristic, demonstrated the best performance. The DL model performed similarly with simulated stream discharge as the critical variable, indicating that simulated discharge can be a potential surrogate. The cross-correlation analysis showed that precipitation, stream discharge, and temperature influence the winter periods' nitrate dynamics. For the other three seasons (e.g., Summer, Fall, and Spring) except winter, stream discharge was the most significant environmental for stream nitrate variabilities. This comprehensive study offers crucial insights into developing a spatially and temporally robust data-driven modeling framework for continuous stream nitrate estimation. The study results will help understand nitrate dynamics at data-limited locations, isolate the period for water withdrawal, optimize the new nitrate sensors installing locations, and design appropriate conservation practices to restrict landscape nitrate transport.

Download or read book Residence Times and Nitrate Transport in Ground Water Discharging to Streams in the Chesapeake Bay Watershed written by and published by . This book was released on 2003 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Seasonal Nitrate Dynamics in an Agriculturally Influenced New Hampshire Headwater Stream written by Catherine Rutherford Dunlap and published by . This book was released on 2010 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Biology and Ecology of Streams and Rivers written by Alan Hildrew and published by Oxford University Press. This book was released on 2023-06-19 with total page 481 pages. Available in PDF, EPUB and Kindle. Book excerpt: The challenges that the world's running water systems now face have never been more numerous or acute; at the same time, these complex habitats remain absolutely crucial to human wellbeing and future survival. If rivers can ever be anything like sustainable, ecology needs to take its place as an equal among the physical sciences such as hydrology and geomorphology. A real understanding of the natural history and ecology of running waters must now be brought even more prominently into river management. The primary purpose of this textbook is to provide the up-to-date overview that students and practitioners will require to achieve this aim. The book's unifying focus is on rivers and streams as ecosystems in which the particular identity of organisms is not the main emphasis but rather the processes in which they are involved - specifically energy flow and the cycling of materials. It builds on the physicochemical foundations of the habitat templet and explores the diversity and adaptations of the biota, progressing from the population and community ecology of organisms and linking them to ecosystem processes and services in the wider biosphere via the complexities of species interactions and food webs. These include water quality and patterns of river discharge, as well as aesthetics, waste disposal, and environmental health. While the book is not primarily focused on application per se, each chapter addresses how humans affect rivers and, in turn, are affected by them. A final, future-oriented chapter identifies key strategic areas and sets a roadmap for integrating knowledge of natural history and ecology into policy and management. The Biology and Ecology of Streams and Rivers is an accessible text suitable for both senior undergraduate and graduate students taking courses in both lotic and general ecology as well as more established researchers, practitioners, managers, and conservationists requiring a concise and contemporary overview of running waters.

Download or read book Spatial and Temporal Analyses of Catchment and In stream Nitrate Dynamics written by Xiaoqiang Yang and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Water quality in river systems is of growing concern due to rising anthropogenic pressures and climate change. Mitigation efforts have been placed under the guidelines of different governance conventions during last decades (e.g., the Water Framework Directive in Europe). Despite significant improvement through relatively straightforward measures, the environmental status has likely reached a plateau. A higher spatiotemporal accuracy of catchment nitrate modeling is, therefore, needed to identify critical source areas of diffuse nutrient pollution (especially for nitrate) and to further guide implementation of spatially differentiated, cost-effective mitigation measures. On the other hand, the emerging high-frequency sensor monitoring upgrades the monitoring resolution to the time scales of biogeochemical processes and enables more flexible monitoring deployments under varying conditions. The newly available information offers new prospects in understanding nitrate spatiotemporal dynamics. Formulating such advanced process ...

Download or read book Handbook of Environmental Materials Management written by Chaudhery Mustansar Hussain and published by Springer. This book was released on 2019-06-03 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This reference work analyzes and assesses global environmental management techniques for environmental materials with a focus on their performance and economic benefits, proposing eco-friendly solutions and designating policies that will sustain the environment for future generations. It addresses management of environmental materials as not only a complex anthropogenic problem, but also as an expensive problem that needs to be managed sustainably. Simultaneously, it considers the environmental and economic benefits involved in the high levels of investment and operation costs required to develop effective materials collection and management systems in modern society.

Download or read book Groundwater Nitrate Transport and Residence Time in a Vulnerable Aquifer Under Dryland Cereal Production written by Christine Ross Miller and published by . This book was released on 2013 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: Selection of agricultural management practices to reduce nitrate leaching from soils can only be successful if both nitrate loading rates from soils to shallow aquifers and groundwater residence times are quantified. Elevated nitrate concentrations in shallow unconfined aquifers are commonly observed in agricultural areas as a result of increased N inputs. In the Judith River Watershed (JRW) in central Montana, USA, notably high nitrate concentrations in groundwater and stream water have exceeded the U.S. EPA drinking water standard of 10 mg L -1 for at least two decades. This large (24,400 ha) watershed drains immediately into the Missouri River, a tributary of the Mississippi River. Over an eleven month period in 2012, we measured groundwater and surface water nitrate concentrations across a hydrologically isolated strath terrace. We use the resulting data to constrain nitrate accumulation dynamics in the shallow aquifer. Nitrate is relatively conservative in this location, as it is high in groundwater (17.57 +/- 4.29 mg L -1; all groundwater samples pooled together), and remains high in streams and springs that drain the landform (15.67 +/- 9.45 mg L -1; all surface water and spring samples pooled together). We use a numerical model to simulate the character of nitrate accumulation in the aquifer as a whole, in order to evaluate how the entire period of cultivation has contributed to current nitrate concentrations, and begin to predict response times for effects of land use change. We consider the effect of groundwater residence time and travel time on nitrate loading using particle tracking in a three dimensional model aquifer. We find no correlation with nitrate concentrations in groundwater and emerging surface waters, and suggest approaches for improving both the geometry of the model and the selection of sites in future work. Overall, our results imply that groundwater residence times are several decades at most, suggesting that similar timeframes will be needed to reduce overall nitrate concentrations in groundwater and emergent streams to below drinking water standards. Preliminary evaluation of several management scenarios suggests that both increased fertilizer use efficiency and rotational strategies may be needed to prevent the loss of soil N to groundwater.

Download or read book Linkages Among Land Use Riparian Zones and Uptake and Transformation of Nitrate in Stream Ecosystems written by Daniel J. Sobota and published by . This book was released on 2008 with total page 302 pages. Available in PDF, EPUB and Kindle. Book excerpt: Land use alters the physical and biological structure of stream ecosystems and potentially alters their capacity to process nitrogen (N), an essential nutrient that has nearly doubled in abundance on the biosphere during the past century from human activities. In this dissertation, I quantified uptake and transformation of nitrate (NO3 ̄) in small (_ third-order) streams and related these dynamics to aquatic ecosystem processes, including primary production and organic matter decomposition, and attributes of riparian zone structure and vegetation composition. I also analyze patterns of stream NO3 ̄ processing among three classes of adjacent land use practices (forest, agriculture, and urban). In Chapter 2, ambient rates of NO3 ̄ uptake and transformation were measured with 24-hr releases of 15N-labeled NO3 ̄ in nine stream reaches in the Willamette River Basin of western Oregon during summer low flow (July - August). Three reaches each were surrounded by forested, agricultural or urban land use. After standardizing reaches to a 500-m length, I estimated that _20% of tracer 15NO3 ̄ was taken up by detrital and autotrophic biomass in eight of the reaches. In the remaining stream, which had the largest discharge (120 L s−1) in this study, only 8% of the tracer was taken up in 500 m. Tracer labeling of detritus and autotrophic biomass and a positive correlation (r[subscript s]=0.81) of uptake with gross primary production suggested that assimilation was the dominant uptake pathway in all streams. Denitrification, dissimilatory reduction of NO3 ̄ to N2 and N2O gases, composed 3 - 15% of 15N budgets over 500 m in two agricultural reaches and in one urban reach dominated by large slowly-turning over pools. However, denitrification was below detection limit at five of the remaining six reaches. This study showed that pathways of stream NO3 ̄ uptake and transformation differed among streams adjacent to three diverse land use practices. In Chapter 3, I quantified effects of substrate nutritional quality and inorganic N loading (as NO3 ̄) on wood breakdown in western Oregon streams. Short-term ( 2 month) breakdown rates of wood substrates of high nutritional quality (Alnus rubra; red alder) and low quality (Pseudotsuga menziesii; Douglas-fir) increased with dissolved inorganic N (11 to 111 [mu]g N L−1 ) across six streams (p = 0.04), but this relationship was confounded with concurrent increases in stream temperature. Across the six streams, breakdown rates of red alder were consistently double that of Douglas-fir. A longer-term study (313 d) in a coniferous forest Oregon Cascades stream suggested effects of increased NO3 ̄ availability on wood breakdown became evident after cellulose and lignin components of woody tissues began to decompose ( 4 months of incubation). Average breakdown rates substrates enriched with NO3 ̄ were higher than those incubated in low NO3 ̄ conditions, but this difference was not statistically significant. However, microbial biofilm respiration rates and activity of two enzymes involved in the breakdown of woody tissues (beta-glucosidase and phenol oxidase) on red alder had significantly greater responses to NO3 ̄ additions than on Douglas-fir after four months of incubation in the stream. Results suggest that increases in N loading to streams bordered by riparian forests with fast-growing deciduous species could increase wood breakdown rates. On the other hand, increases to N loading may have a smaller effect on wood breakdown in streams surrounded by long-lived coniferous species. In Chapter 4, I quantified patterns of stream channel and riparian zone attributes for 72 streams equally distributed among forests or grasslands, agriculture, and urban land use practices on from eight major North American regions. I also related these patterns to stream NO3 ̄ uptake determined from 15NO3 ̄ tracer releases. Agricultural and urban streams had a simplified channel structure (low width-to-depth ratio, low variation in stream depth, and high stream banks) relative to forest or grassland streams. Agricultural and urban streams also had a significantly smaller median sediment diameter (D50) and fraction of benthic sediments composed by silt than in forest and grassland streams. Overstory canopy cover over the channel and in the riparian zone was lowest for agricultural streams but did not significantly differ between forest or grassland streams and urban streams. A multiple regression model showed that stream NO3 ̄ uptake decreased with increasing canopy cover, but also increased with abundance of silt in benthic sediments. This suggested NO3 ̄ uptake was strongly influenced by in-stream primary production and extent of anoxic environments (conducive for denitrification). A multiple regression model for fractional NO3 ̄ uptake by denitrification further supported the concept that extent of anoxic environments influenced overall NO3 ̄ uptake in streams. Through these studies, I demonstrated that attributes of riparian zone structure and vegetation composition can strongly influence NO3 ̄ uptake and transformation in stream ecosystems by controlling organic matter dynamics. I also have shown that riparian zone attributes vary significantly among three different land use types (forest or grassland, agriculture, and urban). Similarly, pathways of NO3 ̄ uptake and effects of NO3 ̄ on wood breakdown did or were expected to differ among different land use types / riparian zone characteristics. However, other factors besides riparian attributes, particularly level of nutrient loading, alteration of stream channel physical structure, and basin position of the stream, must be considered in concert when evaluating effects of land use on riparian zone and stream ecosystem structure and function.

Download or read book Understanding the Influence of Nutrients on Stream Ecosystems in Agricultural Landscapes written by Mark D. Munn and published by United States Department of the Interior. This book was released on 2018 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt: "National Water-Quality Assessment Project."