@article {KNZ001775, title = {Dissolved organic carbon concentration and flux in a grassland stream: spatial and temporal patterns and processes from long-term data}, journal = {Biogeochemistry}, volume = {125}, year = {2015}, pages = {393 - 408}, abstract = {

Dissolved organic carbon (DOC) in streams is a critical component of the global carbon cycle, but little is known about long-term patterns in DOC concentration and export in grassland streams. Here we present the results of a 15-year dataset collected from multiple sites in the Kings Creek watershed on Konza Prairie, KS, USA. DOC concentrations ranged from 0.15 to 15.97 mg L\−1, with a mean of 1.19 mg L\−1 (standard deviation 1.01 mg L\−1). Sites differed in their DOC concentrations as a function of the year of study and the season. Generally, headwaters had greater DOC concentrations, and DOC decreased downstream. The lowest concentrations were found in a groundwater spring in the watershed. Concentrations showed no trend over the study and were not correlated with discharge. However, annual export (mean: 0.29 kg ha\−1 year\−1; range: 0.00\–9.09 kg ha\−1 year\−1) was highly correlated with annual runoff, and annual runoff explained over 80 \% of the variation in export. Export from Kings Creek was 30 times lower than the literature-reported mean for grasslands and 137 times less than export averaged across all biomes. Neither fire nor bison, two forces that maintain prairies, were statistically related to DOC concentrations. Main drivers of DOC concentrations are likely leaching from terrestrial organic material in soils and the accumulations in dry streambeds during drought periods as well as instream autotrophic production. Downstream declines in DOC concentrations suggest instream processing. Grassland streams probably have modest effects on the global carbon budget due to instream processing and low precipitation. Changes in precipitation may have large effects on carbon export from grassland streams.

}, keywords = {LTER-KNZ, carbon cycle, Carbon export, long-term study, prairie streams}, doi = {10.1007/s10533-015-0134-z}, url = {https://link.springer.com/article/10.1007\%2Fs10533-015-0134-z}, author = {R{\"u}egg, J. and Eichmiller, J.J. and Mladenov, N. and W. K. Dodds} } @article {KNZ001522, title = {Woody vegetation removal stimulates riparian and benthic denitrification in tallgrass prairie}, journal = {Ecosystems}, volume = {16}, year = {2013}, pages = {547 -560}, abstract = {

Expansion of woody vegetation into areas that were historically grass-dominated is a significant contemporary threat to grasslands, including native tallgrass prairie ecosystems of the Midwestern United States. In tallgrass prairie, much of this woody expansion is concentrated in riparian zones with potential impacts on biogeochemical processes there. Although the effects of woody riparian vegetation on denitrification in both riparian soils and streams have been well studied in naturally wooded ecosystems, less is known about the impacts of woody vegetation encroachment in ecosystems that were historically dominated by herbaceous vegetation. Here, we analyze the effect of afforestation and subsequent woody plant removal on riparian and benthic denitrification. Denitrification rates in riparian soil and selected benthic compartments were measured seasonally in naturally grass-dominated riparian zones, woody encroached riparian zones, and riparian zones with woody vegetation removed in two separate watersheds. Riparian soil denitrification was highly seasonal, with the greatest rates in early spring. Benthic denitrification also exhibited high temporal variability, but no seasonality. Soil denitrification rates were greatest in riparian zones where woody vegetation was removed. Additionally, concentrations of nitrate, carbon, and soil moisture (indicative of potential anoxia) were greatest in wood removal soils. Differences in the presence and abundance of benthic compartments reflected riparian vegetation, and may have indirectly affected denitrification in streams. Riparian soil denitrification increased with soil water content and NO3 \−. Management of tallgrass prairies that includes removal of woody vegetation encroaching on riparian areas may alter biogeochemical cycling by increasing nitrogen removed via denitrification while the restored riparian zones return to a natural grass-dominated state.

}, keywords = {LTER-KNZ, denitrification, nitrogen removal, prairie streams, riparian vegetation, tallgrass prairie, woody encroachment}, doi = {10.1007/s10021-012-9630-3}, url = {https://link.springer.com/article/10.1007\%2Fs10021-012-9630-3}, author = {Reisinger, A.J. and John M. Blair and C. W. Rice and W. K. Dodds} } @article {KNZ001434, title = {Direct and indirect effects of central stoneroller (Campostoma anomalum) on mesocosm recovery following a flood: can macroconsumers affect denitrification?}, journal = {Journal of the North American Benthological Society}, volume = {30}, year = {2011}, pages = {840 -852}, abstract = {

Anthropogenic N loadings and perturbations of macroconsumer communities impair ecological and economic services provided by streams. Organisms are adapted to natural disturbances, such as flooding and desiccation, but how anthropogenic and natural disturbances interact is poorly understood. We used large outdoor mesocosms to study the effect of Campostoma anomalum, a common prairie headwater-stream minnow, and NH4+ additions (to simulate fish excretion) on the recovery of ecosystem structure and function following a flood, highlighting the potential for Campostoma (and other macroconsumers) to affect denitrification. Campostoma and NH4+ treatments differentially affected particulate organic matter size and filamentous algal structure. Ecosystem structure responded differently to mesocosm treatment over time, a result suggesting that grazers or NH4+-N availability may be especially important during early recovery periods. The presence of Campostoma did not influence denitrification, but NH4+ additions altered the response of denitrifiers to nutrient and energy amendments, and denitrification rates decreased following the recovery of mesocosms. Temporal changes in denitrification probably were caused by increasing hyporheic dissolved O2 concentrations, which led to potentially fewer anoxic microsites for production of denitrification enzymes. Our study shows that grazers affect the recovery of ecosystem structure, but denitrification in the context of these prairie-stream mesocosms appears to be unaffected by Campostoma.

}, keywords = {LTER-KNZ, Campostoma, denitrification, Ecosystem function, Flood, grazer, mesocosm, prairie streams, recovery}, doi = {10.1899/10-169.1}, url = {https://www.journals.uchicago.edu/doi/10.1899/10-169.1}, author = {Reisinger, A.J. and Presuma, D.L. and K. B. Gido and W. K. Dodds} } @mastersthesis {KNZ001331, title = {Factors affecting denitrification in headwater prairie streams}, volume = {MS Thesis}, year = {2010}, school = {Kansas State University}, type = {M.S. Thesis}, address = {Manhattan, KS}, abstract = {

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.

}, keywords = {LTER-KNZ, Biodiversity, denitrification, Ecosystem recovery, nitrogen, prairie streams, woody encroachment}, url = {http://hdl.handle.net/2097/4273}, author = {Reisinger, A.J.} } @article {KNZ001108, title = {Effects of the herbivorous minnow, southern redbelly dace (Phoxinus erythrogaster) on stream ecosystem structure and function}, journal = {Oecologia}, volume = {151}, year = {2007}, pages = {69 -81}, abstract = {We used field and mesocosm experiments to measure effects of southern redbelly dace (Phoxinus erythrogaster), a grazing minnow, on stream ecosystem structure and function. Ecosystem structure was quantified as algal filament length, algal biomass, size distribution of particulate organic matter (POM), algal assemblage structure, and invertebrate assemblage structure, whereas ecosystem function was based on gross and net primary productivity. Our experiments showed that moderate densities of Phoxinus temporarily reduced mean algal filament length and mean size of POM relative to fishless controls. However, there was no detectable effect on algal biomass or ecosystem primary productivity. Several factors could explain the lack of effect of Phoxinus on primary productivity including increased algal production efficiency in grazed treatments or increased grazing by other organisms in fishless treatments. The inability of Phoxinus to reduce algal biomass and system productivity contrasts with experimental results based on other grazing minnows, such as the central stoneroller (Campostoma anomalum), and questions the generality of grazer effects in stream ecosystems. However, environmental venue and the spatial and temporal scale of ecosystem measurements can greatly influence the outcome of these experiments.}, keywords = {LTER-KNZ, grazers, prairie streams, Stream metabolism}, doi = {10.1007/s00442-006-0569-y}, author = {Bertrand, K.N. and K. B. Gido} } @article {KNZ00897, title = {Resistance and resilience of macroinvertebrate assemblages to drying and flood in a tallgrass prairie stream system}, journal = {Hydrobiologia}, volume = {597}, year = {2004}, pages = {99 -112}, abstract = {Intermittent streams are common worldwide, and the ability of invertebrates to recover from floods and drought is a key feature of communities from these highly disturbed ecosystems. The macroinvertebrate assemblages of Kings Creek in northeastern Kansas were sampled regularly from four intermittent and two perennial sites over 2 years (1995{\textendash}1996) to investigate the response and recovery to seasonal drying and floods. A ≈9mo drying period reduced taxa richness and density to 14\% and 3\% of pre-drying assemblages, respectively, in 1995{\textendash}1996, whereas a 2mo drying period reduced richness by half and density to 4\% of pre-drying assemblages in 1996. Floods at intermittent sites reduced densities and richness by 95\% and ≈50\%, respectively. A >50 y-flood reduced macroinvertebrate richness by 97\% and density by >99\% at a downstream perennial site. Resistance and resilience of total macroinvertebrate density was typically greater to floods than to drying, whereas resilience of taxa richness did not differ between disturbance types. The time required for recovery to pre-flood conditions (richness and density) was half as long (27 vs. 76 day) for intermittent sites compared to perennial sites. Colonization of intermittent sites was a function of distance from upstream refugia. Floods were a more important disturbance on assemblages in a downstream reach as compared to upstream reaches. In contrast, upstream reaches were more likely to dry. Recovery following flood and drought was dominated by colonization as opposed to tolerance, thus resilience is more important than resistance in regulating macroinvertebrate communities in these streams, and relative position in the landscape affects disturbance type, intensity, and ability of communities to recover from disturbance.}, keywords = {LTER-KNZ, disturbance, drying, floods, intermittent streams, macroinvertebrates, prairie streams}, url = {http://link.springer.com/article/10.1023/B:HYDR.0000043188.53497.9b}, author = {Fritz, K.M. and W. K. Dodds} }