Tallgrass Prairie Stream Research Articles

Upland Rootzone Soil Water Deficit Regulates Streamflow in a Catchment Dominated by North American Tallgrass Prairie

Intermittent tallgrass prairie streams depend on surface runoff and are highly susceptible to hydrological disturbances such as droughts. The objective of this study was to investigate the timing of intermittent streamflow pulses and upstream rootzone soil water deficit in a watershed dominated by tallgrass prairie. The study was conducted from July to December 2021 in the Kings Creek watershed located within the Konza Prairie Biological station, Kansas, USA. Hourly precipitation and soil moisture observations in the 0–10, 10–30, and 30–50 cm depth were obtained from a hydrological network consisting of 16 monitoring stations across the Kings Creek watershed. Rootzone soil water storage (S) was computed at hourly time steps as the sum of the soil water storage of each soil layer. A drained upper limit (DUL) was estimated as the soil moisture remaining 24 h after the soil had been thoroughly wetted during large (~100 mm) rainfall events. A lower limit (LL) was estimated as the lowest rootzone soil water storage during the study period. Hourly soil water deficit (D) was computed as D = (DUL − S)/(DUL − LL). The study period had 19 precipitation events totaling 436 mm, and only 14 out of the 19 precipitation events exceeded a common canopy and litter interception threshold of 4 mm for tallgrass prairies in this region. Only two precipitation events resulted in measurable streamflow, and the inception of these two streamflow events was associated with a negative weighted soil water deficit (i.e., S > DUL). This pilot study revealed that upland rootzone soil water deficit plays a major role controlling the timing of streamflow in the Kings Creek watershed and possibly in other catchment areas with intermittent prairie streams.

Responses and resilience of tallgrass prairie streams to patch‐burn grazing

Abstract Patch‐burn grazing (PBG) can promote terrestrial heterogeneity and biodiversity, but can temporarily increase stream nutrients and ecosystem metabolism, and alter macroinvertebrate assemblages. The impacts of grazing on stream channel morphology and post‐PBG recovery patterns are unclear. We assessed the influence of grazing in PBG managed grassland streams in Missouri, USA, and subsequent recovery when grazing ceased for 2 years. We hypothesized that grazing would degrade water quality, stream biotic integrity and channel morphology, but that riparian fencing would mitigate these effects. We predicted that biological and chemical variables in unfenced streams would return to pre‐PBG levels within 2 years after grazing ceased, but channel morphology would not. Six small headwater streams (two in ungrazed control watersheds, two in PBG watersheds with 10 m fenced riparian zones and two in PBG unfenced) were sampled over 7 years; 2 years before PBG, 3 years during PBG and 2 years post‐PBG. We sampled macroinvertebrates and water chemistry monthly when water was present and surveyed channel morphology at least once each study period. During grazing, unfenced watersheds showed the greatest changes in channel width, depth and area. During the post‐PBG period, one of the two unfenced watersheds showed partial recovery of channel morphology. Although grazing increased concentrations of nutrients and chlorophyll‐a, concentrations returned to pre‐PBG conditions after grazing ceased, indicating recovery. Very fine organic sediments increased in the unfenced watersheds compared to the control during grazing but recovered afterwards. Contributions of Chironomidae to total invertebrate abundance increased in the unfenced watersheds during grazing, and then decreased during the post‐PBG period. Riparian fencing mostly mitigated effects of grazing on the streams. Unfenced streams were resilient to effects of grazing in a PBG managed grassland, with most metrics recovering within 2 years after grazing ceased, except for channel morphology. Synthesis and applications. Grazing in a patch‐burn grazed managed grassland coupled with riparian fencing could be an effective conservation tool for land managers of prairies, with relatively modest influences on stream water quality and biotic integrity. Persistent changes in stream channel morphology and effects of longer periods of grazing deserve further research.

Fish Communities in Pools and Riffles of Fox Creek, Tallgrass Prairie National Preserve, Chase County, Kansas

We sampled fishes in Fox Creek at Tallgrass Prairie National Preserve, Chase Co., Kansas in June 2012 to record fish species present and to compare richness, abundance, and evenness between pools and riffles. We collected 31 fish species from 94 pools and 14 riffles. The most common species in riffles were Orangethroat Darter (Etheostoma spectabile), Redfin Shiner (Lythrurus umbratilis), and Central Stoneroller (Compostoma anomalum), and the most common species in pools were Redfin Shiner, Central Stoneroller, and Orangespotted Sunfish (Lepomis humilis). Species richness and abundance were higher in pools than riffles, however evenness was not statistically significantly different. Since this study was conducted in the middle of a severe drought, these results could provide important data on how fish communities are assembled during periods of low-flow in tallgrass prairie streams.

The first to arrive and the last to leave: colonisation and extinction dynamics of common and rare fishes in intermittent prairie streams

Summary The objectives of our research were to examine commonness–rarity patterns in fish communities in networks of intermittent streams. We quantified species abundance distributions and the importance of nestedness and turnover to community dissimilarity and then related commonness to colonisation, extinction and physiological tolerance. Patterns and relationships were evaluated spatially among sites and temporally within sites during non‐drought and drought periods in tallgrass prairie streams of eastern Kansas, U.S.A. Supra‐seasonal drought during 2011–2013 resulted in complete or partial drying of some sites and provided an opportunity to evaluate whether commonness was predictive of rather than predicted by colonisation and extinction. Abundance was used to predict re‐colonisation in desiccated reaches and persistence in drying pools. Few species were common, while most were rare regardless of drought, and nestedness drove community dissimilarity across sites. Common species had higher colonisation and lower extinction than rarer species, but physiological tolerance was unrelated to commonness. Abundant species were generally the first to re‐colonise desiccated reaches, but pre‐drought abundance did not predict persistence in partially desiccated reaches. Although common species were the first to colonise and the last to go extinct, we were unable to determine whether commonness was predictive of rather than predicted by colonisation and extinction. Regardless, our study demonstrates linkages among commonness, colonisation and extinction.

Patch-Burn Grazing Effects on the Ecological Integrity of Tallgrass Prairie Streams.

Conversion to agriculture, habitat fragmentation, and the loss of native grazers have made tallgrass prairie one of the most endangered ecosystems. One management option for the remaining prairie parcels, patch-burn grazing (PBG), applies a controlled burn to a portion of the prairie to attract cattle, creating a mosaic of more- and less-grazed patches. Although beneficial to cattle and grassland birds, the potential impacts of PBG on streams have not been studied, and a holistic approach is needed to ensure against adverse effects. We used a Before-After-Control-Impact design to assess potential impacts of PBG with and without riparian protection on tallgrass prairie headwater streams. We sampled stream macroinvertebrates and benthic organic matter 2 yr before and 2 yr during PBG treatments on two grazed watersheds with riparian fencing (fenced), two unfenced grazed watersheds (unfenced), and two ungrazed (control) watersheds. Very fine benthic organic matter increased significantly (51%) in unfenced streams compared with controls ( < 0.007), and fine particulate organic matter (<1 mm and >250 µm) increased 3-fold in the unfenced streams compared with controls ( = 0.008). The contribution of fine inorganic sediments to total substrata increased 28% in unfenced streams during PBG, which was significantly different from controls ( = 0.03). Additionally, the abundance of Ephemeroptera, Plecoptera, and Trichoptera taxa decreased from 7635 to 687 individuals m in unfenced streams, which was significantly lower than in control streams ( = 0.008). Our results indicate that PBG adversely influences prairie streams through sediment inputs and reductions in sensitive invertebrate taxa, but riparian fencing can alleviate these impacts.

Effects of experimental forest removal on macroinvertebrate production and functional structure in tallgrass prairie streams

Encroachment by woody vegetation is a major threat to tallgrass prairie streams, and converts them from open- to closed-canopy systems. This change presumably shifts the relative importance of basal resources from autochthonous to allochthonous and may alter functional feeding group composition and production of consumers. Riparian trees were removed from 2 headwater stream reaches on the Konza Prairie Biological Station to examine effects of forest encroachment and removal. Removal reaches were compared to reaches with naturally open and closed canopies before and after manipulation. Benthic organic matter and macroinvertebrates were sampled monthly for 1 y before (year 1) and after (year 2) riparian forest removal. Total secondary production in removal reaches ranged from 8.9 to 10.2 g ash-free dry mass (AFDM) m−2 y−1 in year 1, and increased significantly to 13.4 to 14.5 g AFDM m−2 y−1 in year 2. Scraper production in removal reaches was 2.8 to 3.9 g AFDM m−2 y−1 in year 1, and increased significantly to 6.0 to 8.7 g AFDM m−2 y−1 in year 2. Shredders did not respond negatively to the removal, but scrapers dominated production (45–60% of total) in open and removal reaches after manipulation. Total production in naturally open reaches was 7.6 to 12.6 g AFDM m−2 y−1 in year 1 and decreased to 6.5 to 9.8 g AFDM m−2 y−1 in year 2. Riparian forest removal altered macroinvertebrate production and functional structure, but higher production in removal reaches than in open reaches after manipulation suggested that natural conditions were not restored 1 y after removal. However, ordinations indicated communities in open and removal reaches became more similar after manipulation. Forest encroachment alters prairie stream structure and function, and riparian forest removal may be an effective restoration and management practice for remaining prairie streams.

Fire and grazing influences on rates of riparian woody plant expansion along grassland streams.

Grasslands are threatened globally due to the expansion of woody plants. The few remaining headwater streams within tallgrass prairies are becoming more like typical forested streams due to rapid conversion of riparian zones from grassy to wooded. Forestation can alter stream hydrology and biogeochemistry. We estimated the rate of riparian woody plant expansion within a 30 m buffer zone surrounding the stream bed across whole watersheds at Konza Prairie Biological Station over 25 years from aerial photographs. Watersheds varied with respect to experimentally-controlled fire and bison grazing. Fire frequency, presence or absence of grazing bison, and the historical presence of woody vegetation prior to the study time period (a proxy for proximity of propagule sources) were used as independent variables to predict the rate of riparian woody plant expansion between 1985 and 2010. Water yield was estimated across these years for a subset of watersheds. Riparian woody encroachment rates increased as burning became less frequent than every two years. However, a higher fire frequency (1–2 years) did not reverse riparian woody encroachment regardless of whether woody vegetation was present or not before burning regimes were initiated. Although riparian woody vegetation cover increased over time, annual total precipitation and average annual temperature were variable. So, water yield over 4 watersheds under differing burn frequencies was quite variable and with no statistically significant detected temporal trends. Overall, burning regimes with a frequency of every 1–2 years will slow the conversion of tallgrass prairie stream ecosystems to forested ones, yet over long time periods, riparian woody plant encroachment may not be prevented by fire alone, regardless of fire frequency.

Blazing and grazing: influences of fire and bison on tallgrass prairie stream water quality

AbstractFire and grazers (such as Bison bison) were historically among the most important agents for maintaining and managing tallgrass prairie, but we know little about their influences on water-quality dynamics in streams. We analyzed 2 y of data on total suspended solids (TSS), total N (TN), and total P (TP) (3 samples per week per stream during flow) in 3 prairie streams with fire and bison grazing treatments at Konza Prairie Biological Station, Kansas (USA), to assess whether fire and bison increase the concentrations of these water-quality variables. We quantified the spatial and temporal locations of bison (∼0.21 animal units/ha) with Global Positioning System collars and documented bison trails, paw patches, wallows, and naturally exposed sediment patches within riparian buffers. Three weeks post-fire, TN and TP decreased (t-test, p < 0.001), but TSS did not change. Bison spent <6% of their time within 10 m of the streams, increased the amount of exposed sediment in the riparian areas, and avoided...

Habitat Associations of Stream Fishes in Protected Tallgrass Prairie Streams

Abstract Describing fish habitat associations and their relevance to conservation remains a central challenge in stream fish ecology. Unfortunately, there are limited opportunities to investigate these associations in unaltered systems and identify critical habitats used by native fishes. Investigation of fish habitat associations in tallgrass prairie is especially vital, owing to their widespread destruction. Our study aim was to identify habitat factors associated with the distribution and density of fishes in two protected tallgrass prairie stream watersheds in eastern Kansas: Kings Creek on the Konza Prairie Biological Station (KPBS) and Fox Creek on the Tallgrass Prairie National Preserve (TPNP). We sampled fishes and measured eight habitat variables at three sites on KPBS (2006–2011) and four sites on TPNP (2008–2011). Multiple regression suggested that species richness was positively associated with pool area (partial r = 0.70) and discharge (partial r = 0.50) in Fox Creek (df = 15, Adj. R2 ...

Ecosystem Characteristics of Remnant, Headwater Tallgrass Prairie Streams

North America has lost >95% of its native tallgrass prairie due to land conversion, making prairie streams one of the most endangered ecosystems. Research on the basic ecosystem characteristics of the remaining natural prairie streams will inform conservation and management. We examined the structure and function of headwater streams draining tallgrass prairie tracts at Osage Prairie in Missouri and the Konza Prairie Biological Station in Kansas and compared those values with literature values for streams draining agricultural watersheds in the region. We quantified physicochemical and biological characteristics for 2 yr. Streams at Osage and Konza were characterized by low nutrients and low suspended sediments (substantially lower than impacted sites in the region), slight heterotrophic status, and high temporal variability. Suspended sediments and nutrient concentrations were generally low in all prairie streams, but storms increased concentrations of both by 3- to 12-fold. Spring prescribed burns were followed by a slight increase in chlorophyll and decreased nutrients, potentially due to greater light availability. Benthic macroinvertebrate communities at Osage showed seasonal patterns that were probably linked to variable hydrology. We found nine amphibian species using the Osage streams as habitat or breeding sites, but little usage at Konza was probably due to dry conditions and low discharge. Our study indicates that two remnant tallgrass prairie streams along a longitudinal gradient are fairly similar in terms of physicochemical features and have good water quality relative to agricultural watersheds but can differ considerably in macroinvertebrate and amphibian abundance.

Patterns of macroinvertebrate production, trophic structure, and energy flow along a tallgrass prairie stream continuum

We estimated benthic organic matter standing stocks, macroinvertebrate production, food‐web structure, and stream metabolism along a longitudinal continuum of Kings Creek at Konza Prairie Biological Station in Kansas. Benthic macroinvertebrates were sampled for 1 yr from three stream reaches (grass, shrub, gallery forest). Total habitat‐weighted production ranged from 9.1 g to 31.9 g ash‐free dry weight m−2 yr−1 with the grass headwaters accounting for the highest production. Functional group contributions to production were similar along the continuum, with collector–gatherers (40–56% of total) and predators (23–38%) dominating all reaches. Detrital pathways appeared to account for most energy flow in all reaches, and all reaches were net heterotrophic on all dates when metabolism was measured, except for the grass headwater reach in spring. Predators were well‐represented and consumed 65–107% of total macroinvertebrate production, whereas scrapers (11–15%), shredders (2–4%), and filterers (&lt; 1%) consumed relatively small percentages of available resources. Dominance of predators suggested top‐down controls are important in this system. However, changes in energy flow through other groups reflected longitudinal variation in resource availability. This prairie stream continuum conforms to some predictions of conceptual stream continua models, but biotic interactions, which are often not considered, may override some predicted responses to changes in the physical template.

Life history and production of the riffle beetle, Stenelmis crenata (Say, 1824) (Coleoptera: Elmidae), in a tallgrass prairie stream

We examined life history dynamics and estimated production of the riffle beetle, Stenelmis crenata (Say, 1824), in a tallgrass prairie stream. Stenelmis crenata had a univoltine life cycle with larvae present year-round. Recruitment of first instars occurred from June–October, larval growth was synchronised through the winter, pupation occurred in late spring, and adults first appeared in late May. Adults were most abundant (24 individuals/m2) during summer and were present in samples through October. For larval biomass and production estimates, a body length–mass relationship (ash-free dry mass [AFDM] = 0.0079*TL2.7595) was constructed. Mean annual density and biomass of larvae were 235 individuals/m2 and 90.7 mg AFDM/m2, respectively. Annual larval production was 493 mg/m2/y, representing a total of ∼101 g AFDM for the stream reach examined. Production estimates for S. crenata in this stream were high compared to other estimates for elmids, and this species comprised an appreciable portion of total scraper (13.5%) production.

Resistance and Resilience of Macroinvertebrate Assemblages to Drying and Flood in a Tallgrass Prairie Stream System

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 (1995–1996) 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 1995–1996, 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.

Ecosystem significance of crayfishes and stonerollers in a prairie stream: functional differences between co-occurring omnivores

The ecosystem significance of crayfishes (Orconectes nais (Faxon) and O. neglectus (Faxon)) and central stoneroller minnows (Campostoma anomalum (Rafinesque)), was examined in a tallgrass prairie stream by estimating the trophic basis of production and consumption for each species. Annual ash-free dry mass production and production to biomass ratios of C. anomalum (260 mg m−2 y−1, 1.3) were lower than that of O. nais (719 mg m−2 y−1, 2.4) and O. neglectus (508 mg m−2 y−1, 2.1). Gut content analysis revealed no significant differences in the percentages of the various food items ingested by O. nais and O. neglectus, indicating they were functionally similar with respect to the types of organic matter processed in this system. We found a significant difference among seasons in the % of invertebrates in C. anomalum guts (p = 0.0001) and the % of algae in Orconectes spp. guts (p = 0.005), indicating the importance of measuring resource use throughout the growing season. Leaves contributed most to Orconectes spp. annual production (45%) followed by animal matter (30%), algae (19%), and amorphous detritus (6%). Algae contributed most to C. anomalum production (47%) followed by amorphous detritus (30%), animal matter (21%), and leaves (2%). Orconectes spp. consumed more leaf litter, filamentous green algae, and macroinvertebrates than C. anomalum, whereas C. anomalum consumed more diatoms. Crayfish and central stonerollers are both omnivores that function as important consumers and processors of algae and detritus in this tallgrass prairie stream, but each focuses on slightly different types of similar resources.

Recovery of Three Fish Species to Flood and Seasonal Drying in a Tallgrass Prairie Stream

The recovery of three fish species following a catastrophic flood (>50 y recurrence interval) and seasonal drying were studied in Kings Creek basin at the Konza Prairie Biological Station in northeastern Kansas. Fish collected from three tallgrass prairie headwater springs were marked and recaptured to determine if headwater springs were a source of fish recolonizing intermittent sections downstream and to estimate population sizes in the headwater springs. Three fish species (Campostoma anomalum, Phoxinus erythrogaster, and Etheostoma spectabile) were collected. Catch rates and population estimates of fish nine days post-flood were approximately half of the values obtained during subsequent sampling periods. Recolonization of an intermittent section was primarily by age-0 fish that seemingly were displaced downstream by flood events. The distribution of fish within the upper subbasins of the South Branch of Kings Creek was limited to perennial spring-fed reaches. The short duration of continuous flow and regular drying in these tributaries might limit the dispersal of individuals between populations in this landscape.

Macroinvertebrate Production and Trophic Structure in a Tallgrass Prairie Headwater Stream

Research on North American prairie stream communities has lagged behind other regions. We examined the ecosystem significance of the macroinvertebrate community of riffle/run habitats in Kings Creek, a 2^nd-order tallgrass prairie stream at Konza Prairie Biological Station (Kansas, USA), by estimating secondary production, benthic organic matter standing stocks, and resource consumption and egestion by functional groups. Annual mean standing stock macroinvertebrate biomass was 2.3 g ash-free dry mass (AFDM)/m², annual production was 19.7 g AFDM m^-2 y^-1, and the annual community production/biomass (P/B) ratio was 8.6. Macroinvertebrate production was higher than published estimates for forested streams of similar size, but much lower than that of a Sonoran desert stream. Distribution of production among functional groups was 30% for collector-gatherers, 9% for collector-filterers, 20% for scrapers, 23% for shredders, and 18% for predators, resembling estimates from some forested streams with the exception of higher scraper production. Although detritivorous groups were productive in this prairie stream, they appeared food limited. Consumption estimates indicated shredders and collector-gatherers annually ingested ∼80% and ∼240% of coarse particulate organic matter (CPOM) and fine particulate organic matter (FPOM) standing stocks, respectively. Thus, re-ingestion and/or diet shifts may be common, particularly among collector-gatherers, and the FPOM pool must turn over rapidly. Invertebrate predators also consumed a sizeable portion (∼52%) of prey, whereas scrapers (∼21%) and filterers (<1%) consumed relatively small portions of their respective resources, suggesting top-down influences on these groups. This study indicates that, during a period of relatively stable flow in this prairie stream, macroinvertebrate production and functional structure were roughly intermediate between North American forested and desert systems. Our results underscore the value of secondary production estimates for examining invertebrate communities in an ecosystem context.

A comparison of the trophic ecology of the crayfishes (Orconectes nais (Faxon) and Orconectes neglectus (Faxon)) and the central stoneroller minnow (Campostoma anomalum (Rafinesque)): omnivory in a tallgrass prairie stream

Omnivorous fish, such as the central stoneroller minnow (Campostoma anomalum(Rafinesque)), and crayfish often play important roles in the trophic dynamics of streams. The trophic role of these two omnivores has not been compared within a system even though they both consume algae, detritus and invertebrates and often co-occur in streams in the Midwestern United States. Natural abundance of 15N and 13C isotopes and a whole stream 15N-labeled ammonium chloride release were used to compare the trophic ecology of the central stoneroller minnow (Campostoma anomalum (Rafinesque)) and two species of crayfish (Orconectes neglectus (Faxon) and Orconectes nais (Faxon)) in a tallgrass prairie stream. The δ15N and δ13C values of Orconectes spp. were more similar to coarse benthic organic matter (CBOM) and filamentous green algae than to invertebrates, fine benthic organic matter (FBOM), and periphyton. Values for δ15N and δ13C in C. anomalum were more similar to grazer and collector invertebrates and filamentous green algae than to FBOM and periphyton. Results from a 15N tracer release also indicated a portion of algae and/or invertebrates were a component of nitrogen assimilated in Orconectes spp. and C. anomalum diets. Gut contents of C. anomalum were also analyzed. In contrast to stable isotope data, amorphous detritus was a significant component of C. anomalum guts, followed by diatoms and filamentous green algae. A significant percentage of invertebrate material was found in C. anomalum guts sampled in the spring. Experiments were conducted in artificial streams to determine if Orconectes spp. and C. anomalum could reduce epilithic algal biomass in small streams. Algal biomass on clay tile substrata was decreased relative to controls in artificial stream channels containing O. neglectus (3.4 fold, p=0.0002), C. anomalum (2.1 fold, p=0.0012), and both species combined (3.0 fold, p=0.0003). Results indicate that Orconectes spp. are functioning more as algal and detrital processors than as predators in Kings Creek. Isotope and gut content data show that C. anomalum includes invertebrates as well as algae and detritus in its diet. Both species have the potential to affect algal biomass and are important omnivores in the stream food web.

The Effects of Bison Crossings on the Macroinvertebrate Community in a Tallgrass Prairie Stream

Abstract The distribution and diversity of macroinvertebrates in relation to bison crossings was studied for four seasons in a headwater reach of a tallgrass prairie stream. Species richness was significantly higher above crossings only during the fall. Summer samples revealed significantly higher EPT (richness within only Ephemeroptera, Plecoptera and Trichoptera) index values above crossings than at crossings. On average, over 10% more fine sediment (<0.2 mm) occurred at the crossings than above or below crossings. Densities of two taxa (Hydropsyche spp. and Elmidae) were significantly higher above or below crossings, whereas three taxa (Bezzia/Palpomyia spp., Culicoides sp., and Naididae/Tubificidae) were significantly higher at crossings for at least one season. Overall, this study suggests that impact of bison on benthic communities of headwater streams was spatially limited. Although bison may have less impact upon stream communities than previous studies of cattle impacts have shown, differences in...

Response of Insectivorous Birds to Emerging Aquatic Insects in Riparian Habitats of a Tallgrass Prairie Stream

The relationship between emergence production of aquatic insects from Kings Creek, a taligrass prairie stream, and densities of insectivorous birds (flycatcher and gleaner guilds) was examined using concurrent measurements of insect emergence and bird densities at six sites on 31 dates during May to July from 1987 to 1990. Daily insect emergence averaged 10.6 g/100-reach in the gallery forest habitat and 2.5 g/reach in the prairie/shrub habitat. Principal taxa included Chironomidae (> 50% of emergence biomass), Ephemeroptera and Plecoptera. Common flycatchers were the eastern wood-pewee (Contopus virens) and great crested flycatcher (Myiarchus crinitus) in the gallery forest, and eastern kingbird (Tyrannus tyrannus) in the prairie/shrub habitat. Common gleaners were black- capped chickadee (Parus atricapillus) in the gallery forest and common yellowthroat (Geoth- lypis trichas) in the prairie/shrub. Flycatcher densities were highly correlated with total emergence in both habitats, but gleaner densities were correlated with emergence only in the gallery forest habitat. Both emergence and insectivore densities varied directly with the stream hydrograph, even over short, postflood recovery periods. Direct observations of feeding behavior showed that insectivores preyed upon a variety of aquatic and nonaquatic prey. Thus stream insects are an important food resource for insectivorous birds in riparian habitats of the tallgrass prairie, although insect emergence is likely insufficient to support observed insectivore densities.

Patterns and Controls of Nitrogen in Tallgrass Prairie Streams

A descriptive and experimental approach was used to study patterns of nitrogen concentrations in tallgrass prairie streams in Kansas. Nitrate concentrations varied depending on the year, season, time of day, stream flow conditions, source of water, and location where the sample was taken. Mean nitrate concentrations during the dormant season decreased from 1982 to 1984, corresponding to above—normal precipitation during this same period. Nitrate concentrations decreased from third—order (grass/shrub riparian vegetation) to fourth—order channels (gallery forests). Nitrate, organic N, and total N were higher in a third—order intermittent stream than in a third—order perennial stream. Water from seeps and tributaries had higher nitrate concentrations than stream water; however, streams and tributaries had higher organic N than seeps. Maximum nitrate concentrations during storm flows were directly related to the frequency of storm events. The activity of terrestrial vegetation influenced nitrate concentrations within streams, seeps, and tributaries; nitrate concentrations were always higher during periods of vegetation dormancy. Aquatic biota influenced both spatial patterns (downstream decrease in nitrate concentrations and increase in organic N) and diel patterns of nitrate concentration (night &gt; day). Uptake rates of nitrate by biota were greater during the day than during the night as determined by experimental addition of nitrate. Nitrogen (N) and/or phosphorus (P) limitations of algal growth were tested experimentally using nutrient—diffusing substrata (clay saucers filled with enriched agar) and enrichment of artificial channels. Addition of N and P in combination increased algal biomass (chlorophyll a and ash—free dry mass) over controls or single addition of N or P. Thus, algal biomass was N and P limited; however, individual taxa responded to specific N and/or P concentrations or atomic N:P ratio.