Effects of Riparian Woody Vegetation Encroachment on Prairie Stream Structure and Function with Emphasis on Whole-stream Metabolism PDF Download
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Author: Alyssa J. Riley Publisher: ISBN: Category : Languages : en Pages :
Book Description
Much of the North American tallgrass prairie ecosystem has been converted to cropland or urbanized. One threat to the remaining prairie ecosystems, and the streams within, is woody vegetation encroachment. Stream productivity, measured as metabolism, is a fundamental process comprised of gross primary production (GPP) and (CR) community respiration. Understanding GPP and CR is important because these processes are vital to ecosystem function and can be impacted by a change in canopy cover. First, I investigated improvements in existing methods for estimating whole-stream metabolism as estimated from diel patterns of oxygen (O2). I compared measured and modeled O2 and aeration (a physical parameter required for measurement of metabolism) rates to determine if direct measurement of aeration is necessary and the importance of temperature correction of metabolism. Modeling was moderately successful in determining aeration rates, and temperature correction of GPP and CR substantially improved model fits. Second, effects of woody vegetation encroachment on prairie stream function were investigated. Stream metabolism was measured for four years in duplicate reaches with varying canopy cover (closed canopy, naturally open canopy, and vegetation removal reaches). The removal reaches had closed canopy for the first two years and open canopy for the last two years. Canopy cover increased CR rates and had minimal effects on GPP. Third, the same experiment was used to determine the effects of woody vegetation encroachment on prairie stream ecosystem structure and food web interactions. Chlorophyll a and filamentous algal biomass were greater in naturally open and vegetation removal reaches, although the effects were stronger on filamentous algal biomass. As canopy cover decreased, the filamentous algal biomass to chlorophyll ratio increased, indicating a shift in algal community structure. Stable isotope analysis indicated some shift in pathways of nitrogen and carbon flux into the food web related to degree of canopy cover, but overlap in the signature of food sources made distinct food sources difficult to identify. The data indicate that riparian encroachment can influence ecosystem structure and function in prairie streams and restoration to remove woody riparian cover may restore some ecosystem features of naturally open canopy streams.
Author: Alyssa J. Riley Publisher: ISBN: Category : Languages : en Pages :
Book Description
Much of the North American tallgrass prairie ecosystem has been converted to cropland or urbanized. One threat to the remaining prairie ecosystems, and the streams within, is woody vegetation encroachment. Stream productivity, measured as metabolism, is a fundamental process comprised of gross primary production (GPP) and (CR) community respiration. Understanding GPP and CR is important because these processes are vital to ecosystem function and can be impacted by a change in canopy cover. First, I investigated improvements in existing methods for estimating whole-stream metabolism as estimated from diel patterns of oxygen (O2). I compared measured and modeled O2 and aeration (a physical parameter required for measurement of metabolism) rates to determine if direct measurement of aeration is necessary and the importance of temperature correction of metabolism. Modeling was moderately successful in determining aeration rates, and temperature correction of GPP and CR substantially improved model fits. Second, effects of woody vegetation encroachment on prairie stream function were investigated. Stream metabolism was measured for four years in duplicate reaches with varying canopy cover (closed canopy, naturally open canopy, and vegetation removal reaches). The removal reaches had closed canopy for the first two years and open canopy for the last two years. Canopy cover increased CR rates and had minimal effects on GPP. Third, the same experiment was used to determine the effects of woody vegetation encroachment on prairie stream ecosystem structure and food web interactions. Chlorophyll a and filamentous algal biomass were greater in naturally open and vegetation removal reaches, although the effects were stronger on filamentous algal biomass. As canopy cover decreased, the filamentous algal biomass to chlorophyll ratio increased, indicating a shift in algal community structure. Stable isotope analysis indicated some shift in pathways of nitrogen and carbon flux into the food web related to degree of canopy cover, but overlap in the signature of food sources made distinct food sources difficult to identify. The data indicate that riparian encroachment can influence ecosystem structure and function in prairie streams and restoration to remove woody riparian cover may restore some ecosystem features of naturally open canopy streams.
Author: Jodi M. Vandermyde Publisher: ISBN: Category : Languages : en Pages : 186
Book Description
Woody vegetation encroachment has become a major threat to tallgrass prairie streams mainly because of fire suppression. This process converts prairie streams from open to closed canopy systems. The effects of these riparian changes are poorly understood, but the relative importance of basal resources presumably shifts from primarily autochthonous to allochthonous with increasing canopy cover, potentially altering macroinvertebrate functional structure and production. To assess the effects of woody vegetation encroachment on stream ecosystem structure and function, riparian trees were removed from two headwater stream reaches on the Konza Prairie Biological Station (KPBS) in eastern Kansas. Experimental stream reaches were compared to streams with naturally open and closed canopies before and after the manipulation. Riparian forest removal altered macroinvertebrate production and functional structure, but higher macroinvertebrate production in canopy removal reaches compared to naturally open reaches suggested natural conditions were not restored one year after riparian removal. However, macroinvertebrate communities in naturally open and canopy removal reaches became more similar after riparian removal. Functional structure, based on production, in naturally open and canopy removal reaches after riparian removal was dominated by scrapers (45-60% of total production), with similar proportions of collector-gatherers (12-26%) and predators (15-25%). Collector-filterers and shredders contributed
Author: Alexander Joseph Reisinger Publisher: ISBN: Category : Languages : en Pages :
Book Description
Human-induced stressors such as increased nitrogen (N) loadings, altered watershed land-use, and biodiversity losses are a few of the numerous threats to aquatic systems. Prairie streams experience natural disturbances, such as flooding and desiccation, which may alter responses to anthropogenic stressors. Denitrification, the dissimilatory reduction of NO3- to N gas (N2O or N2), is the only permanent form of N removal from terrestrial or aquatic ecosystems, and is important in mitigating N pollution to streams and downstream waters. Little is known about the relationships between denitrification and riparian prairie vegetation or large consumers. In the first chapter, I used outdoor mesocosms to determine the impact of a grazing minnow, Campostoma anomalum, on structural and functional responses of prairie streams to a simulated flood, focusing on denitrification. In terrestrial ecosystems, grazing can stimulate denitrification, but this has not been studied in streams. Ammonium (NH4+) enrichments, used to simulate fish excretion, alleviated N limitations on denitrification. Both fish and NH4+ affected algal biomass accrual, but only fish affected algal filament lengths and particulate organic matter. In a second experiment, I examined the impact of woody vegetation expansion, a primary threat to tallgrass prairie, on riparian and benthic denitrification. Expansion of woody vegetation in these grasslands is due primarily to altered fire regimes, which historically inhibited woody vegetation growth. To determine the effect of woody vegetation expansion on benthic and riparian denitrification, woody vegetation was removed from the riparian zone of a grazed and an ungrazed watershed. Both soil and benthic denitrification rates from this removal buffer were compared to rates in grassy or woody riparian zones. Riparian soil denitrification was highly seasonal, with greatest rates occurring during early spring, and rates being low throughout the remainder of the year. Benthic denitrification was also temporally variable but did not exhibit seasonal trends, suggesting benthic denitrification is driven by factors other than water temperature. Removal of woody vegetation stimulated soil and benthic denitrification rates over rates found in naturally vegetated riparian zones. Elevated N loadings will continue to affect aquatic ecosystems, and these effects may be exacerbated by biodiversity losses or changing riparian vegetation.
Author: Claire Marie Ruffing Publisher: ISBN: Category : Languages : en Pages :
Book Description
Geomorphic properties of streams are linked to ecosystem function through processes related to storage, transport, and other drivers regulating biogeochemical conditions. Disturbances altering the physical template of a stream are associated with cascading impacts on ecosystem function. However, few disturbances are studied at long time scales and so the legacy of such events and the implications for ecosystem structure and function are not well understood. This research investigates the role of historic tie-driving, a channel disturbance legacy, in shaping present-day stream channel conditions in the Rocky Mountain region and the associated implications for organic matter dynamics. Using a combination of geomorphic and riparian surveys, organic matter and vegetation sampling, and modeling, I show that components of mountain stream ecosystems have recovered from tie-driving at varying rates. First, I addressed how tie-driving has altered channel morphology and wood loading. Tie-driven streams are narrower, shallower, less rough, and have less wood than non-driven reference reaches. In a second study, I focused on differences in carbon storage within the stream and riparian area between tie-driven and non-driven streams. Carbon stored on the landscape represents a long-term component of the terrestrial carbon cycle and some, but not all, components have been impacted by tie-driving. Large instream wood, coarse downed wood, and fine downed wood were identified as carbon storage components that were significantly smaller in tie-driven stream-riparian corridors. Finally, I modeled whole stream ecosystem metabolism and tested whether abiotic drivers influenced variations in rates of gross primary productivity (GPP), ecosystem respiration (ER), and net ecosystem productivity (NEP). Results from this work suggest that rates of GPP were significantly different between tie-driven and non-driven streams and were partially explained by variations in light related to canopy structure. However, variations in ER and NEP were not significantly different between tie-driven and non-driven sites. Taken as a whole, this work shows that ecosystems bear the imprint of historic disturbances but individual ecosystem components recover at differing rates. Additionally, integrating stream hydro-geomorphic and ecological dynamics is an effective approach to understanding the impact of channel disturbances in shaping ecosystem function at a variety of spatial and temporal scales.
Author: Alyssa J. Riley
Author: Alyssa J. Riley
Author: Jodi M. Vandermyde
Author: Alexander Joseph Reisinger
Author: Kenneth W. Cummins
Author: Robert B. Jacobson
Author: Christopher Todd Kaase
Author: Dean Frederick Messer
Author: M. Alice Walters
Author: Claire Marie Ruffing
Author: Martin Palt