Location matters: evaluating Greater Prairie-Chicken (Tympanuchus cupido) boom chorus propagation

Anthropogenic disturbances can affect species of conservation concern by influencing their behavior. Of special concern is the possibility that noise from anthropogenic structures in grassland habitats, such as wind turbines and roads, may affect the propagation of the low-frequency boom chorus of lekking male Greater Prairie-Chickens (Tympanuchus cupido). We used sound pressure levels from acoustic recordings taken at 10 leks in the Nebraska Sandhills, USA during 2013 and 2014 in a SPreAD-GIS sound propagation model to make spatial projections of the boom chorus under a variety of conditions including landscape composition, conspecific attendance, and weather. We then used sets of linear mixed models in a model selection process to determine how background noise, female and male lek attendance, time of day, relative humidity, air temperature, and wind speed affected the area of chorus propagation. The predicted area of propagation decreased with increasing background noise (β = -0.09, SE = 0.04) and increased with greater female lek attendance (β = 0.09, SE = 0.03), higher levels of relatively humidity (β = 0.07, SE = 0.03), and higher air temperatures (β = 0.05, SE = 0.03). Our analyses provide new insight on how acoustic, social, and meteorological factors influence an important reproductive behavior in an imperiled prairie grouse

Temporal variability in large grazer space use in an experimental landscape

Land use, climate change, and their interaction each have great potential to affect grazing systems. With anticipated more frequent and extensive future drought, a more complete understanding of the mechanisms that determine large grazer landscape-level distribution under varying climatic conditions is integral to ecosystem management. Using an experimental setting with contrasting fire treatments, we describe the inter-annual variability of the effect of landscape topography and disturbance from prescribed spring fire on large grazer space use in years of variable resource availability. Using GPS telemetry, we investigated space use of plains bison (Bison bison bison) as they moved among watersheds managed with variable experimental burn treatments (1-, 2-, 4-, and 20-year burn intervals) during a seven-year period spanning years of average-to-above average forage production and severe drought. At the landscape scale, bison more strongly favored high-elevation and recently burned watersheds with watersheds burned for the first time in 2 or 4 yr consistently showing higher use relative to annually burned watersheds. In particular, watersheds burned for the first time in 4 yr were avoided to lesser extent than other more frequently burned watersheds during the dormant season. This management type also maintained coupling between bison space use and post-fire regrowth across post-drought growing season months, whereas watersheds with more frequent fire-return intervals attracted bison in only the first month post-fire. Hence, fire frequency played a role in maintaining the coupling of grazer and post-fire regrowth, the fire–grazer interaction, in response to drought-induced reduction in fuel loads. Moreover, bison avoided upland habitat in poor forage production years, when forage regrowth is less likely to occur in upland than in lowland habitats. Such quantified responses of bison to landscape features can aid future conservation management efforts and planning to sustain fire–grazer interactions and resulting spatial heterogeneity in grassland ecosystems

Temporal variability in large grazer space use in an experimental landscape

Land use, climate change, and their interaction each have great potential to affect grazing systems. With anticipated more frequent and extensive future drought, a more complete understanding of the mechanisms that determine large grazer landscape-level distribution under varying climatic conditions is integral to ecosystem management. Using an experimental setting with contrasting fire treatments, we describe the inter-annual variability of the effect of landscape topography and disturbance from prescribed spring fire on large grazer space use in years of variable resource availability. Using GPS telemetry, we investigated space use of plains bison (Bison bison bison) as they moved among watersheds managed with variable experimental burn treatments (1-, 2-, 4-, and 20-year burn intervals) during a seven-year period spanning years of average-to-above average forage production and severe drought. At the landscape scale, bison more strongly favored high-elevation and recently burned watersheds with watersheds burned for the first time in 2 or 4 yr consistently showing higher use relative to annually burned watersheds. In particular, watersheds burned for the first time in 4 yr were avoided to lesser extent than other more frequently burned watersheds during the dormant season. This management type also maintained coupling between bison space use and post-fire regrowth across post-drought growing season months, whereas watersheds with more frequent fire-return intervals attracted bison in only the first month post-fire. Hence, fire frequency played a role in maintaining the coupling of grazer and post-fire regrowth, the fire–grazer interaction, in response to drought-induced reduction in fuel loads. Moreover, bison avoided upland habitat in poor forage production years, when forage regrowth is less likely to occur in upland than in lowland habitats. Such quantified responses of bison to landscape features can aid future conservation management efforts and planning to sustain fire–grazer interactions and resulting spatial heterogeneity in grassland ecosystems

Hyperspectral Analysis of Leaf Pigments and Nutritional Elements in Tallgrass Prairie Vegetation

Understanding the spatial distribution of forage quality is important to address critical research questions in grassland science. Due to its efficiency and accuracy, there has been a widespread interest in mapping the canopy vegetation characteristics using remote sensing methods. In this study, foliar chlorophylls, carotenoids, and nutritional elements across multiple tallgrass prairie functional groups were quantified at the leaf level using hyperspectral analysis in the region of 470–800 nm, which was expected to be a precursor to further remote sensing of canopy vegetation quality. A method of spectral standardization was developed using a form of the normalized difference, which proved feasible to reduce the interference from background effects in the leaf reflectance measurements. Chlorophylls and carotenoids were retrieved through inverting the physical model PROSPECT 5. The foliar nutritional elements were modeled empirically. Partial least squares regression was used to build the linkages between the high-dimensional spectral predictor variables and the foliar biochemical contents. Results showed that the retrieval of leaf biochemistry through hyperspectral analysis can be accurate and robust across different tallgrass prairie functional groups. In addition, correlations were found between the leaf pigments and nutritional elements. Results provided insight into the use of pigment-related vegetation indices as the proxy of plant nutrition quality

Regulation of hepatic cytochrome P450 expression in mice with intestinal or systemic infections of citrobacter rodentium.

We reported previously that infection of C3H/HeOuJ (HeOu) mice with the murine intestinal pathogen Citrobacter rodentium caused a selective modulation of hepatic cytochrome P450 (P450) gene expression in the liver that was independent of the Toll-like receptor 4. However, HeOu mice are much more sensitive to the pathogenic effects of C. rodentium infection, and the P450 down-regulation was associated with significant morbidity in the animals. Here, we report that oral infection of C57BL/6 mice with C. rodentium, which produced only mild clinical signs and symptoms, produced very similar effects on hepatic P450 expression in this strain. As in HeOu mice, CYP4A mRNAs and proteins were among the most sensitive to down-regulation, whereas CYP4F18 was induced. CYP2D9 mRNA was also induced 8- to 9-fold in the C57BL/6 mice. The time course of P450 regulation followed that of colonic inflammation and bacterial colonization, peaking at 7 to 10 days after infection and returning to normal at 15 to 24 days as the infection resolved. These changes also correlated with the time course of significant elevations in the serum of the proinflammatory cytokines interleukin (IL)-6 and tumor necrosis factor-alpha, as well as of interferon-gamma and IL-2, with serum levels of IL-6 being markedly higher than those of the other cytokines. Intraperitoneal administration of C. rodentium produced a rapid down-regulation of P450 enzymes that was quantitatively and qualitatively different from that of oral infection, although CYP2D9 was induced in both models, suggesting that the effects of oral infection on the liver are not due to bacterial translocation

Complex variation in habitat selection strategies among individuals driven by extrinsic factors

Understanding behavioral strategies employed by animals to maximize fitness in the face of environmental heterogeneity, variability, and uncertainty is a central aim of animal ecology. Flexibility in behavior may be key to how animals respond to climate and environmental change. Using a mechanistic modeling framework for simultaneously quantifying the effects of habitat preference and intrinsic movement on space use at the landscape scale, we investigate how movement and habitat selection vary among individuals and years in response to forage quality–quantity tradeoffs, environmental conditions, and variable annual climate. We evaluated the association of dynamic, biotic forage resources and static, abiotic landscape features with large grazer movement decisions in an experimental landscape, where forage resources vary in response to prescribed burning, grazing by a native herbivore, the plains bison (Bison bison bison), and a continental climate. Our goal was to determine how biotic and abiotic factors mediate bison movement decisions in a nutritionally heterogeneous grassland. We integrated spatially explicit relocations of GPS-collared bison and extensive vegetation surveys to relate movement paths to grassland attributes over a time period spanning a regionwide drought and average weather conditions. Movement decisions were affected by foliar crude content and low stature forage biomass across years with substantial interannual variation in the magnitude of selection for forage quality and quantity. These differences were associated with interannual differences in climate and growing conditions from the previous year. Our results provide experimental evidence for understanding how the forage quality–quantity tradeoff and fine-scale topography drives fine-scale movement decisions under varying environmental conditions

Location matters: evaluating Greater Prairie-Chicken (Tympanuchus cupido) boom chorus propagation

Anthropogenic disturbances can affect species of conservation concern by influencing their behavior. Of special concern is the possibility that noise from anthropogenic structures in grassland habitats, such as wind turbines and roads, may affect the propagation of the low-frequency boom chorus of lekking male Greater Prairie-Chickens (Tympanuchus cupido). We used sound pressure levels from acoustic recordings taken at 10 leks in the Nebraska Sandhills, USA during 2013 and 2014 in a SPreAD-GIS sound propagation model to make spatial projections of the boom chorus under a variety of conditions including landscape composition, conspecific attendance, and weather. We then used sets of linear mixed models in a model selection process to determine how background noise, female and male lek attendance, time of day, relative humidity, air temperature, and wind speed affected the area of chorus propagation. The predicted area of propagation decreased with increasing background noise (β = -0.09, SE = 0.04) and increased with greater female lek attendance (β = 0.09, SE = 0.03), higher levels of relatively humidity (β = 0.07, SE = 0.03), and higher air temperatures (β = 0.05, SE = 0.03). Our analyses provide new insight on how acoustic, social, and meteorological factors influence an important reproductive behavior in an imperiled prairie grouse

Moderate Grazer Density Stabilizes Forage Availability More Than Patch Burning in Low-Stature Grassland

Spatially patchy fire creates landscape-level diversity that in turn stabilizes several rangeland ecosystem services, including forage production and habitat availability. To enhance biodiversity and livestock production, efforts are underway to restore fire regimes in rangelands throughout the Great Plains. However, invasive species such as tall fescue Schedonorus arundinaceus syn. Festuca arundinacea, initially introduced for forage production, hamper prescribed fire use. Grazer density, or stocking rate, modulates the effect of patchy fire regimes on ecological patterns in invaded, seminatural rangeland pastures. We compare three diversity–stability responses—temporal variability in aboveground plant biomass, portfolio effects among plant functional groups, and beta diversity in plant functional group composition—in pastures managed with two different fire regimes through three periods of heavy, light, and moderate stocking rate in southern Iowa, USA. Pastures were either burned in patches, with one-third of the pasture burned each year, or completely burned every third year. The period of moderate grazer density had the least temporal variability in aboveground plant biomass, regardless of fire regime. We also found statistical evidence for a portfolio effect under moderate stocking, where diversification of plant communities through varying cover of functional groups can stabilize communities by reducing year-to-year variability. Beta diversity among plant functional groups was greatest during the moderate grazer density period as well. The short stature of tall fescue prevented the patch-burning regime to create contrast in vegetation structure among patches, and there was no difference in any diversity–stability mechanism response across the two different patterns of burning. Although longitudinal, these data suggest that temporal variability in aboveground plant biomass declines with diversity–stability mechanisms that underlie ecosystem function. Our results also support a decades-old principle of range management: moderate grazing intensity enhances diversity and stability, which has been shown to buffer forage shortfalls during drought

Present and future thermal environments available to Sharp-tailed Grouse in an intact grassland

<div><p>Better understanding animal ecology in terms of thermal habitat use has become a focus of ecological studies, in large part due to the predicted temperature increases associated with global climate change. To further our knowledge on how ground-nesting endotherms respond to thermal landscapes, we examined the thermal ecology of Sharp-tailed Grouse (<i>Tympanuchus phasianellus</i>) during the nesting period. We measured site-specific iButton temperatures (T_iB) and vegetation characteristics at nest sites, nearby random sites, and landscape sites to assess thermal patterns at scales relevant to nesting birds. We asked if microhabitat vegetation characteristics at nest sites matched the characteristics that directed macrohabitat nest-site selection. Grouse selected sites sheltered by dense vegetation for nesting that moderated T_iB on average up to 2.7°C more than available landscape sites. Successful nests were positioned in a way that reduced exposure to thermal extremes by as much as 4°C relative to failed nests with an overall mean daytime difference (±SE) of 0.4 ±0.03°C. We found that macrohabitat nest-site selection was guided by dense vegetation cover and minimal bare ground as also seen at the microhabitat scale. Global climate projections for 2080 suggest that T_iB at nest sites may approach temperatures currently avoided on the landscape, emphasizing a need for future conservation plans that acknowledge fine-scale thermal space in climate change scenarios. These data show that features of grassland landscapes can buffer organisms from unfavorable microclimatic conditions and highlight how thermal heterogeneity at the individual-level can drive decisions guiding nest site selection.</p></div