Elizabeth Bach - Above- and belowground response to dominant grass removal on tallgrass prairie (Mentors: Gail Wilson and Charles Rice).
Big Bluestem (Andropogon gerardii) and Indian Grass (Sorghastrum nutans) are the dominant warm season grasses on the tallgrass prairie and affect both above ground plant communities and the belowground microbial community structure.  This study follows the long-term changes in the above- and belowground communities and soil characteristics resulting from the removal of A. gerardii and S. nutans from plots in two watersheds of the Konza Prairie Biological Research Station.  In the initial years after grass removal, treated plots showed large differences in plant species composition, mycorrhizal root colonization, and nematode community structure.  Removal plots had significantly less mycorrhizal colonization, fewer herbivorous nematodes, and more plant species richness.  An intensive study ten years after the removal investigated above- and belowground parameters including plant species composition, total soil C and N, soil microbial biomass C and N, phospholipid fatty acid (PLFA) content, neutral lipid fatty acid (NLFA) content, soil aggregation, the nematode community, and arbuscular mycorrhizal fungi root colonization.  Average above ground cover of A. gerardii was still different between treatments, but average cover of S. nutans appeared to have recovered.  After ten years, Tall Dropseed (Sporobolus asper) had increased in the removal plots.   All belowground variables showed that the removal plots had recovered.  The study did reveal distinct differences in the belowground communities of the two watersheds studied, despite identical burn regimes and similar elevation.

Aaron Berdanier - How pressing is increased nitrogen?  Rethinking plant responses and the pulse paradigm (Mentor: John Blair).
Human activity in the last century has greatly increased the amount and mobility of biologically-available nitrogen (N) in the biosphere. In terrestrial ecosystems, increased N deposition can significantly alter ecosystem processes, such as productivity, C storage and nutrient cycling, and is a threat to plant diversity and long-term soil fertility.  Much of our understanding of the effects of elevated N deposition comes from field fertilization experiments, which are consequently important for predicting future ecosystem responses to N enrichment.  Most of these nutrient addition experiments are conducted with discrete, “pulsed” nutrient applications (i.e., once per year).  However, actual increases in nutrient inputs (e.g., elevated atmospheric N deposition), occur in a more continuous, or “pressed”, manner.  Fertilization experiments utilizing a pulse approach may not be appropriate for predicting the effects of more continuous inputs.  This experiment was designed to compare the differential effects of equal amounts of N, added either in a single pulse or as a series of smaller amendments across the growing season, on soil N availability and plant responses in native tallgrass prairie. We applied inorganic N (NH₄-NO₃) in solution to 60 experimental plots in irrigated and non-irrigated upland tallgrass prairie; 20 pulsed with a one-time application of 10 g N m^-2 early in the growing season, 20 pressed with 10 additions of 1 g N m^-2 added at 10-day intervals throughout the growing season, and 20 non-fertilized control plots.  Extractable soil N was measured four times during the growing season to assess patterns of soil N availability. At 10 day intervals, leaf samples of Andropogon gerardii were collected from each plot and analyzed for C and N concentrations.  Ceptometer readings were taken above and below the canopy at mid-day on six dates during the growing season to assess canopy light interception as a non-destructive index of canopy growth.  We found strong interactions between irrigation and N treatments across dates for both available soil N and canopy development.  In general, there was significantly greater soil N availability in the pulsed treatment, relative to the pressed treatment or control. Canopy development was positively affected by both N treatments in the irrigated plots only, but the response to the pulse treatment was significantly greater than to the press. There was also significant separation in N treatments for leaf tissue quality as the growing season progressed.  These results suggest that pulsed and pressed N inputs have different effects on soils and plants, and that this should be considered when designing experiments to assess the impact of chronic N enrichment.

Clayton Bowers - The growth cycle of the Common Nighthawk (Chordeiles minor): an unusual mode of development (Mentor: Brett Sandercock).
Unlike many of the bird species around the world, quantitative estimates of growth and development have not been published for nightjars (F. Caprimulgidae).  Nightjars are difficult to study because they have cryptic plumage, crepuscular activity, and an overall secretive way of life. This field study is one of the first investigations of the development in the young of any nightjar. Growth rates of nighthawks are of interest for at least two reasons. First, nighthawks have semiprecocial young, a mode of development also found only in unrelated species of marine birds such as terns, gulls, murres, jaegers, and albatrosses.  Second, nighthawks lay their eggs directly on the ground with no nest substrate. I hypothesized that the predation on exposed eggs and young should select for rapid growth. Nests were located on the Konza Prairie in Northeastern Kansas during the summer months of 2006 by observation of aerial adults, and by walking through areas that looked to be potential nesting areas.  I located a sample of 31 nighthawk nests. When nests were located and chicks hatched, five growth characters (head, wing, tail, tarsus, mass) were recorded every two days.  To compare growth data with the asymptotic body size of adults (A), I captured adult nighthawks at night on gravel roads using a spotlight and dip net (n = 2 females, 6 males). A logistic growth curve was fit to the data, and non-linear regression was used to model the intrinsic growth rate (K) and the inflection point (I).  Head (K = 0.14, I = -0.28) and tarsus (K = 0.26, I = -0.62) were quick to reach A, but wing (K = 0.16, I = 16.1) and tail (K = 0.19, I = 20.8) were slower in growth. Degree of asynchrony and brood number were also tested in attempt to find some difference in growth. It was found that the degree of asynchrony was marginally significant for wing and mass in that the first hatched chick of a two chick brood grew somewhat faster (P = 0.07, P = 0.06, respectively). No significance was found for growth between one and two chick broods.

Eric Kightley - Potential effects of the introduced bullhead minnow (Pimephales vigilax) on the native bluntnose minnow (Pimephales notatus) (Mentors: Darren Thornbrugh and Keith Gido).
The bullhead minnow, Pimephales vigilax, was introduced into the Kansas River drainage in 1976 where it now occurs with the native bluntnose minnow, Pimephales notatus. Because they are congeners, we hypothesized P. vigilax would negatively interact with P. notatus. Four possible impacts of P. vigilax on P. notatus were tested: 1) spatial overlap, 2) spawning habitat competition between males, 3) diet overlap, and 4) hybridization. Three tributary creeks were sampled at five locations within 10 km from the Kansas River mainstem to identify spatial overlap. Mesocosms with spawning habitat structures were constructed to observe competition between males. Gut contents from fish caught during field surveys were analyzed to identify diet overlap. Morphometric measurements were taken to identify hybrids. Abundance of P. notatus increases away from the Kansas river, whereas P. vigilax abundance was moderate at all sites Pimephales notatus was dominant over P. vigilax in seven of 10 competition trials for spawning habitat. No significant diet overlap was found, as P. notatus guts were composed mainly of detritus, and P. vigilax mainly invertebrates. Morphometric analysis suggested distinct species with no hybridization. Future research could help elucidate the consequences of increased energy expenditure due to spawning site competition in males, examine the fertility, reproductive, and survival rates of both species. Field studies that remove P. vigilax from spawning sites in a stream to see if P. notatus eventually replaces these fish would help verify the impact of P. vigilax on P. notatus.

Viviana Loaiza - Is phosphorus a limiting nutrient for nymphs of Melanoplus bivittatus (Orthroptera:Acrididae)? (Mentor: Tony Joern).
Food can be highly variable in both availability and nutritional quality, especially for herbivores. Moreover, nutritional needs change depending upon physiological and biochemical requirements resulting from stress or developmental needs. Major nutrients for grasshoppers include N-based proteins/ free amino acids, and C-based carbohydrates/ sugars, as a source of energy, and from which lipids can be derived. While the effects of dietary nitrogen and carbohydrates on grasshoppers are well studied, the importance of phosphorus (P), a third major elemental category, remains unaddressed. Grasshopper performance studies using controlled diets and field-based estimates of herbivory on plants fertilized with nitrogen and phosphorus fertilizer were undertaken In the feeding study, fifth instar nymphs were fed artificial diets consisting of three different ratios of protein and carbohydrate, each crossed with three levels of phosphorus until final molt to the adult stage. In the field, leaf damage on the grass Andropogon gerardi and the forb Solidago missouriensis were estimated; grasshopper densities were measured in P- and N-fertilization plots. The interaction of P with the protein:carbohydrate diet treatment significantly affected the amount of diet consumed but not the amount of frass produced, suggesting a difference in diet assimilation. Growth rate (mass-increase/day) over the developmental stage increased with greater P consumption, possibly due to elevated metabolic rates or ARN transcription. High levels of P in the diet significantly delayed development. In the field, the interaction between phosphorus and nitrogen fertilization was significant with respect to foliar damage from insect herbivores (mostly grasshoppers). A higher grasshopper density (individuals/m2) was observed in all plots fertilized with nitrogen, and no effect of P-fertilization was detected. At the individual level, phosphorus can be limiting as expected. But, when scaling to the population level, other variables (i.e. food palatability) may change the behavior observed so that P-limitation is not readily observed.

Kelsey Reider - A lizard on the rocks: collared lizards and Konza geography (Mentor: Eva Horne).
In the Flint Hills of Kansas, collared lizards (Crotaphytus collaris) appear to depend heavily on the presence of rock outcrops for habitat. At Konza Prairie Biological Station (KPBS), alternating mudstone and limestone layers form slopes and resistant benches, respectively. In various locations around KPBS the resistant benches allow 11 limestone layers to outcrop where the less resistant mudstones have been eroded. Each layer outcrops in characteristic ways, some of which may provide better habitat for collared lizards. I identified which limestone outcrops had lizards and characterized the outcrops to identify habitat differences between them.  Of the 11 limestone layers, lizards or fecal pellets were found on four layers: Cottonwood, Eiss, Funston, and Florence.  The presence of lizards was significantly correlated with rock height (P = 0.013), the availability of refuge spaces (P < 0.001), and percent rock cover (P = 0.002). The presence of refuge spaces appeared to be the most important factor in lizard habitat selection.  The four limestone layers where lizards were found had higher mean refuge spaces than layers without lizards. I also evaluated toe painting as a mark-recapture method, and compared lizard size and parasite loads between two limestone layers. I estimated the population of collared lizards on a 350-meter transect of the Cottonwood limestone to be approximately 11 individuals.  I compared lizard snout-vent length and total chigger load between animals captured on the Cottonwood limestone (n = 9) and those from the Funston limestone (n = 5). Neither parameter was significant, though Cottonwood lizards tended to have larger (2x) chigger loads than the Funston lizards. This study could provide direction for a population census of collared lizards on KPBS.

Loren Reinhardt - Spatial heterogeneity of ammonium uptake in prairie streams (Mentor: Walter Dodds).
Nitrogen uptake has always been thought of as a complex process, but generally researchers sample on a coarse scale in order to increase replication. What information are we sacrificing for replication? There could be smaller scale patterns important to stream nutrient dynamics that have not been seen. In this study, we focused on differences between pool and riffle nitrogen uptake. Today, channelization of streams is causing them and to loose their riffle, pool structure. Knowing how riffles and pools function independently of one another will be key to predicting future changes of stream nutrient retention. We tested these differences by injecting ammonium chloride and sodium bromide (nonconservative and conservative tracers, respectively) into three prairie streams on the Konza LTER during the summer of 2006. On each sampling date we injected at three concentrations, allowing for accurate quantification of spiraling metrics at background rates. We also sampled algae and coarse benthic organic matter (CBOM) standing stocks. We found that in each stream ammonium uptake was greater in riffles (U=0.979- 1.9 μg/m²/s) than in pools (0.0430-1.37 μg/m²/s) with runs tending to fall in the middle (0.428- 1.50 μg/m²/s). Chlorophyll per unit area was the best predictor of uptake (more chlorophyll increases U), whereas CBOM was not a good predictor. As expected, chlorophyll per unit area decreased with increased depth, higher stream velocity and CBOM increased with increased depth, lower stream velocity. It appears that channelizing streams would increase nitrogen retention, but there are other factors such as increased turbidity due to less debris damns that would change this result.

Derek Schook – Microgeographic song variation and the formation of dialects in the Dickcissel (Spiza americana) (Mentor: Tim Parker).
Many songbirds have been shown to demonstrate distinct song dialects in different areas within a population. Most studies, including a 2005 study on Dickcissels in the Flint Hills, have identified dialects by sampling separate sites within a population. In contrast, my study aimed to investigate Dickcissel dialects by viewing song sharing on a continuous scale to explore dialect sizes and the transitional zones that occur between dialects. After recording the songs of 32 banded Dickcissels throughout the breeding season, I conducted a repeatability analysis of six quantitative components in their songs. A high positive correlation (r = 0.70–0.96) revealed that songs do not change over the season. This result validated my comparison of songs recorded at different times throughout the summer. A qualitative analysis of the songs of 578 birds recorded on the Konza Prairie revealed that song syllables do show clustering, which sometimes can be viewed at multiple scales. The additional sampling of 107 birds along three road transects showed inconsistent trends in song component turnover. Sampling at both Konza and on the road transects revealed that Dickcissel song sharing and variation demonstrates complex patterns not clearly revealed by our current analytical methods. Additional analysis, including methods relating to quantitative song measurements and geostatistics, will be explored with these data in the near future.

Emilie Throop – The effects of nest, local and landscape scale habitat features on snake depredation of grassland birds (Mentors: Page Klug and Kimberly With).
In a grassland ecosystem, snakes may play an important role in the nesting success of songbirds. The objectives of this study were to determine if grassland birds and snakes share much of the same preferred habitat, and if nesting success can be modeled through relationships between nest sites and preferred snake habitat features. I radio-tracked Yellow-bellied Racers (Coluber constrictor) and recorded location information such as treatment type and immediate habitat cover. I also monitored nests of the Dickcissel (Spiza americana), Grasshopper Sparrow (Ammodramus savannarum), Lark Sparrow (Chondestes grammacus), Field Sparrow (Spizella pusilla), and Eastern Meadowlark (Sturnella magna). Nest successes and failures that may have been due to snake predation were recorded, and habitat variables at the nest site, local scale, and the landscape scale were measured.  Principal components analysis was run for habitat features such as litter depth, Robel pole readings, distance to shrubs, forest, rock outcrops, treatment edges, and draws for Dickcissels alone and then all species combined. MARK analysis for Dickcissels revealed that shrubby habitat features positively influence nest success. This may be due to the occurrence of both Dickcissels and snakes in shrubby areas, as well as snake foraging strategy. As shrubby habitat increases, there is less chance an incidental predator, such as a snake, might find a nest. MARK analysis for all species combined revealed that an overall heterogeneous habitat positively influences nest success. Because several of the birds monitored have different nesting strategies, the increased nest success due to heterogeneous habitat may be more influenced by nest site preferences than snake predation. These habitat features describe a complex relationship between grassland songbirds and the snake predator community with regards to nest, local and landscape scale characteristics.

Last updated: August 2006