Niche relationships and diet overlaps were compared among elk (Cervus elaphus), bison (Bison bison), bighorn sheep (Ovis canadensis), mule deer (Odocoileus hemionus), and pronghorn antelope (Antilocapra americana) between 1967–1970 and 1986–1988, a period when total ungulate numbers nearly tripled on Yellowstone's northern range. Ungulate species ratios on Yellowstone's northern winter range during the latter period were 100 elk : 10 mule deer : 3 bison : 2 pronghorns : 1 bighorns. Elk numbers were positively correlated to bison, mule deer, and pronghorn numbers (r2 = 0.76, 0.97, and 0.48, respectively, P < 0.01). Few other changes in habitat use or habitat overlap occurred, and diets for only 2 of the 10 species pairs, elk-bighorn (Spearman's rank order coefficient (RHO) = 0.55, P < 0.05) and mule deer – pronghorn (RHO = 0.64, P < 0.05), were significantly associated with each other. Bison consumed more grass and fewer sedges, mule deer more fringed sage (Artemisia frigida) and more rabbit-brush (Chrysothamnus spp.), and bighorn sheep more grasses and fewer sedges, while pronghorns ate less saltsage (Atriplex nuttalli) but more big sagebrush (Artemisia tridentata) during 1986–1988 than during 1967–1970. Bison expanded their range and bison and bighorn sheep used a wider variety of habitats. We found little evidence of change in competitive interactions between ungulate species. A few diet and habitat overlaps increased, the opposite of the prediction from the competitive exclusion principle amongst species, suggesting that intraspecific competition was more important. Several explanations are proposed for the lack of changes in niche relationships during a period of near tripling in density of the ungulate guild.

Landscapes with structural heterogeneity or patchiness can support diverse and stable wildlife populations. Visual obstruction methods (i.e., Robel pole and Nudd's coverboard) are common and useful techniques for quantifying vegetation structure; however, both rely on ocular estimations, which can be highly variable between observers. Our objectives were to 1) compare measurement and observer variation for visual obstruction among the two standard methods and the digital image method we developed using a digital camera; and 2) compare the performance of the Robel pole and digital image to estimate standing crop. The mean variation across the five observers using the digital image method (6.8%) was significantly lower (P , 0.05) than both the Nudds' coverboard (32.1%) and the Robel pole (52.2). There were no significant differences among locations for the digital image method; however, there were for both the Robel pole and Nudds' cover board (P , 0.05). The digital image method provided a better estimate of standing crop (r 2 5 0.89) compared to the Robel pole (r 2 5 0.68), accounting for 21% more of the observed variation in biomass. Long-term research programs that utilize seasonal field technicians to quantify habitat structure with a visual obstruction method could benefit from implementing use of the digital image method we developed. The low measurement error observed with this technique relative to the more traditional methods compared in this study might limit yearto-year and within-year variability of habitat structure data collected by numerous technicians with a high annual turnover. Resumen Los paisajes con una hetrogeneidad estructural o con muchos parches pueden sostener poblaciones diversas y estables de fauna silvestre. Los métodos de obstrucción visual (por ejemplo, el poste de Robel y la tabla de cobertura de Nudd) son te´cnicas comunes y útiles para cuantificar la estructura de la vegetación; sin embargo, ambas dependen de estimaciones oculares, las cuales pueden ser altamente variables entre observadores. Nuestros objetivos fueron: 1) comparar las mediciones y la variación de los observadores en la obstrucción visual entre los dos me´todos estándar y el me´todo de imagen digital que desarrollamos usando una cámara digital; y 2) comparar el comportamiento de los me´todos el poste de Robe y de imagen digital para estimar la biomasa aérea. La variación media entre los cinco observadores usando el método de imagen digital (6.8%) fue significativamente menor (P , 0.05) que los me´todos de la tabla de cobertura de Nudd (32.1%) y el poste de Robel (52.2%). No hubo diferencias significativas entre localidades para el me´todo digital; sin embargo, si la hubo para los me´todos de la tabla de cobertura de Nudd y el poste de Robel (P , 0.05). El método de imagen digital proveyó una mejor estimación de la biomasa (r 2 5 0.89), comparado con el me´todo del poste de Robel (r 2 5 0.68), explicando 21% más de la variación observada en la biomasa. Los programas de investigación a largo plazo que utilizan técnic...

Hyperspectral 1-m-resolution remote sensing has the potential to reduce the time spent sampling and reduce spatial sampling errors found in traditional forage nutritive analysis over large areas. The objective of this study was to investigate if 1-m-resolution hyperspectral techniques are useful tools to provide reliable estimates of forage nitrogen (N), phosphorus (P) and neutral detergent fiber (NDF) in Yellowstone National Park. The vegetative communities investigated varied in the amount of canopy coverage and species diversity, and ranged from xeric, semiarid environments to mesic, wetland/riparian environments. A large number of simple ratio-type vegetation indices (SRTVI) and normalized difference-type vegetation indices (NDTVI) were developed with the hyperspectral dataset. These indices were regressed against N, P, and NDF values from ground collections. We found that 1) there were strong linear relationships between selected SRTVI and N (R 2 ¼ 0.7), P (R 2 ¼ 0.65), and NDF (R 2 ¼ 0.87) nutritive values on an area basis (g m À2); and 2) there were no strong linear relationships (R 2 , 0.3) between a variety of SRTVI and NDTVI and N, P, and NDF on a dry matter basis (g g À1 3 100). The lack of relationship is related to 1) the highly variable relationship between the dry matter biochemical signal and total plant biomass and water content and 2) the weakening of the biochemical signal from exposed soil in low-canopy situations, from nonphotosynthetic vegetation (bark, stems, and litter), and from different plant species. Resumen Los sensores remotos de tipo hiperespectral de 1 m 2 de resolució n tienen el potencial de reducir el tiempo de muestreo y los errores espaciales de muestreo encontrados en los aná lisis tradicionales de calidad del forraje en grandes a ´reas. El objetivo de este estudio fue investigar si las técnicas hiperespectrales de 1 m 2 de resolució n son herramientas u ´ tiles para proveer estimaciones confiables del nitró geno (N), fó sforo (P) y fibra neutro detergente (NDF) del forraje en el Parque Nacional de Yellowstone. Las comunidades vegetales estudiadas variaron en la cantidad de cobertura de copa y diversidad de especies y estuvieron en un rango de ambientes xéricos semiá ridos a ambientes mésico de humedales y ribereñ os. Con el juego de datos de los sensores hiperespectrales se desarrolló un gran nú mero de ı ´ndices del tipo de relació n simple (SRTVI) e ı ´ndices del tipo de Diferencia Normalizada de Vegetació n (NDTVI) que se sometieron a análisis de regresió n contra valores de N, P, y NDF obtenidos de de colecciones en el terreno. Encontramos que: 1) hay relaciones lineales fuertes entre SRTVI y N (R 2 ¼ 0.7), P (R 2 ¼ 0.65), y NDF (R 2 ¼ 0.87), (valores estimados en g m À2). 2) No hubo relaciones lineales fuertes (R 2 , 0.3) entre el N, P y NDF, en base a materia seca (g g À1 3 100), y una variedad de ı ´ndices de SRTVI y NDTVI. La falta de la relació n se esta relacionada con: 1) una relació n altamente variable entre la señ al bioquímica de la materia seca y la biomasa ...

Precision Prairie Reconstruction (PPR) is a site-specific application for enhancing native species richness (specifically, native forbs) in old fields dominated by a few non-native grass species. The method consists of establishing microcommunities of native grasses and forbs in an existing grass matrix. The microcommunities are created by broadcast seeding simulated small-scale disturbances (8.06 m2) installed over a percentage of the site. The PPR results were compared with two standard restoration techniques: herbicide/drill-seeding and rototill/broadcast seeding. A PPR design that disturbed only 25% of the area resulted in total species richness, native grass frequency, and native forb richness, stability, and density over the entire plot that were similar to what was found in the conventional rototill/broadcast method and produced better results than the herbicide/drill-seeding method. The PPR technique involved less cost and less overall disturbance than traditional herbicide application/drill-seeding or rototill/broadcast seeding methods. PPR offers an alternative approach for increasing native grass and forb diversity in old fields dominated by a few non-native grass species.

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