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Articles 1 - 13 of 13
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Long-Term Effects Of Tebuthiuron On Bromus Tectorum, Dana M. Blumenthal, Urszula Norton, Justin D. Derner, Jean D. Reeder
Long-Term Effects Of Tebuthiuron On Bromus Tectorum, Dana M. Blumenthal, Urszula Norton, Justin D. Derner, Jean D. Reeder
Western North American Naturalist
Use of herbicides to thin dense stands of Artemisia spp. (sagebrush) can free up resources for herbaceous plants and increase forage production, but may also facilitate weed invasion. We revisited a sagebrush thinning experiment in a north central Wyoming big sagebrush–grassland 11 years after application of tebuthiuron (N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N-N′-dimethylurea) to determine the long-term responses of shrubs, available soil resources, perennial grasses, and Bromus tectorum L. (downy brome). Tebuthiuron reduced shrub cover by more than half, from 31% in untreated plots to 15% in treated plots (P = 0.002), and increased downy brome cover approximately 4-fold, from 0.9% in untreated plots …
Plant Composition And Erosion Potential Of A Grazed Wetland In The Salmon River Subbasin, Idaho, Kristine N. Hopfensperger, Joan Q. Wu, Richard A. Gill
Plant Composition And Erosion Potential Of A Grazed Wetland In The Salmon River Subbasin, Idaho, Kristine N. Hopfensperger, Joan Q. Wu, Richard A. Gill
Western North American Naturalist
Wetlands are dynamic habitats with many unique, important functions including filtering sediments and providing diverse habitats for fish and wildlife. Wetlands in the western United States are particularly important because they offer habitat for a number of protected runs of endangered fish species. Historically, livestock grazing has altered wetland and riparian area form and function by facilitating exotic species invasions, altering spatial heterogeneity of vegetation, and increasing erosion. In this study we examined vegetation structure and erosion potential in a wetland meadow exposed to unregulated grazing along Deer Creek in the Salmon River subbasin, Idaho. We characterized the vegetation composition …
New Directions And Challenges In Spatial Dynamic Modelling Of Ecosystem Functions In Heterogeneous Landscapes As Basis For A Better Sustainable Landscape Management, Karl-Otto Wenkel, Ralf Wieland, Wilfried Mirschel
New Directions And Challenges In Spatial Dynamic Modelling Of Ecosystem Functions In Heterogeneous Landscapes As Basis For A Better Sustainable Landscape Management, Karl-Otto Wenkel, Ralf Wieland, Wilfried Mirschel
International Congress on Environmental Modelling and Software
The aim of this paper is to discuss scientific challenges and new possibilities for a better modelling of consequences of land use changes in heterogeneous landscapes on ecosystem functions in space and time. The landscape or regional scale means an area of about 100 km2 up to some 1000 km2. Main problems on this scale are high complexity, structural diversity, ecological heterogeneity and uncertainty in data, in understanding of the process dynamic and by uncertainty in models.
Dealing With Uncertainty And Sensitivity Issues In Process-Based Models Of Carbon And Nitrogen Cycles In Northern Forest Ecosystems, G. R. Larocque, J. S. Bhatti, A. M. Gordon, N. Luckai, Jinxun Liu, Shuguang Liu, P. A. Arp, C. -F Zhang, Alexander Komarov, Pavel Grabarnik, M. Wattenbach, C. Peng, Jianfeng Sun, Thomas White
Dealing With Uncertainty And Sensitivity Issues In Process-Based Models Of Carbon And Nitrogen Cycles In Northern Forest Ecosystems, G. R. Larocque, J. S. Bhatti, A. M. Gordon, N. Luckai, Jinxun Liu, Shuguang Liu, P. A. Arp, C. -F Zhang, Alexander Komarov, Pavel Grabarnik, M. Wattenbach, C. Peng, Jianfeng Sun, Thomas White
International Congress on Environmental Modelling and Software
Many process-based models on carbon (C) and nitrogen (N) cycles have been developed for northern forest ecosystems. These models are widely used to evaluate the long-term decisions in forest management dealing with effects like particulate pollution, productivity and climate change. Regarding climate change, one of the key questions that have sensitive political implications is whether northern forests will sequester atmospheric C or not. Whilst many process-based models have been tested for accuracy by evaluating or validating against observed data, few have dealt with the complexity of the incorporated procedures to estimate uncertainties associated with model predictions or the sensitivity of …
Dealing With Uncertainty And Sensitivity Issues In Process-Based Models Of Carbon And Nitrogen Cycles In Northern Forest Ecosystems, G. R. Larocque, J. S. Bhatti, A. M. Gordon, N. Luckai, Jinxun Liu, Shuguang Liu, P. A. Arp, C. -F Zhang, Alexander Komarov, Pavel Grabarnik, M. Wattenbach, C. Peng, Jianfeng Sun, Thomas White
Dealing With Uncertainty And Sensitivity Issues In Process-Based Models Of Carbon And Nitrogen Cycles In Northern Forest Ecosystems, G. R. Larocque, J. S. Bhatti, A. M. Gordon, N. Luckai, Jinxun Liu, Shuguang Liu, P. A. Arp, C. -F Zhang, Alexander Komarov, Pavel Grabarnik, M. Wattenbach, C. Peng, Jianfeng Sun, Thomas White
International Congress on Environmental Modelling and Software
Many process-based models on carbon (C) and nitrogen (N) cycles have been developed for northern forest ecosystems. These models are widely used to evaluate the long-term decisions in forest management dealing with effects like particulate pollution, productivity and climate change. Regarding climate change, one of the key questions that have sensitive political implications is whether northern forests will sequester atmospheric C or not. Whilst many process-based models have been tested for accuracy by evaluating or validating against observed data, few have dealt with the complexity of the incorporated procedures to estimate uncertainties associated with model predictions or the sensitivity of …
New Directions And Challenges In Spatial Dynamic Modelling Of Ecosystem Functions In Heterogeneous Landscapes As Basis For A Better Sustainable Landscape Management, Karl-Otto Wenkel, Ralf Wieland, Wilfried Mirschel
New Directions And Challenges In Spatial Dynamic Modelling Of Ecosystem Functions In Heterogeneous Landscapes As Basis For A Better Sustainable Landscape Management, Karl-Otto Wenkel, Ralf Wieland, Wilfried Mirschel
International Congress on Environmental Modelling and Software
The aim of this paper is to discuss scientific challenges and new possibilities for a better modelling of consequences of land use changes in heterogeneous landscapes on ecosystem functions in space and time. The landscape or regional scale means an area of about 100 km2 up to some 1000 km2. Main problems on this scale are high complexity, structural diversity, ecological heterogeneity and uncertainty in data, in understanding of the process dynamic and by uncertainty in models.
The Effect Of Livestock Grazing On The Rainbow Grasshopper: Population Differences And Ecological Correlates, Sandra J. Debano
The Effect Of Livestock Grazing On The Rainbow Grasshopper: Population Differences And Ecological Correlates, Sandra J. Debano
Western North American Naturalist
This study examined the effect of livestock grazing on a common herbivore in semiarid grasslands of the Southwest: the rainbow grasshopper, Dactylotum variegatum. Population attributes and key environmental variables were compared between sites on active cattle ranches and sites on a 3160-ha ungrazed sanctuary. Although density of D. variegatum nymphs did not differ significantly between grazed and ungrazed sites, adult density was significantly lower on grazed sites, and sex ratios differed between grazed and ungrazed sites over time. Grazed sites had higher percentages of bare ground and fewer Baccharis pteronioides, a common shrub. However, only bare ground was …
Tamarix Aphylla: A Newly Invasive Tree In Southern Nevada, Lawrence R. Walker, Pamela L. Barnes, Elizabeth A. Powell
Tamarix Aphylla: A Newly Invasive Tree In Southern Nevada, Lawrence R. Walker, Pamela L. Barnes, Elizabeth A. Powell
Western North American Naturalist
In the southwestern United States, the nonnative athel pine (Tamarix aphylla) was presumed to be sterile and therefore not as likely to spread as its widely distributed, nonnative congener, T. ramosissima. However, at Lake Mead National Recreation Area (LMNRA) in southern Nevada, populations of T. aphylla have recently spread beyond their limited pre-1990 distribution and now form extensive monospecific stands. Over a 3-year period, we quantified seed production and germination from 60 T. aphylla trees at LMNRA. The annual mean seed production period was 50.6 days, and the mean potential germination (under laboratory conditions) was 22%, indicating …
Characteristics Of Swift Fox Dens In Northwest Texas, Brady K. Mcgee, Kerry L. Nicholson, Warren B. Ballard, Matthew J. Butler
Characteristics Of Swift Fox Dens In Northwest Texas, Brady K. Mcgee, Kerry L. Nicholson, Warren B. Ballard, Matthew J. Butler
Western North American Naturalist
The swift fox (Vulpes velox) was classified in 1995 as a candidate for listing under the Endangered Species Act. Since then, several studies have addressed survey methods for monitoring swift fox populations. The purpose of this paper is to assist field researchers in documenting the presence of swift foxes by identification of recently active den sites. We propose that swift foxes have unique external den characteristics that can be distinguished during aerial surveys. We collected data from 30 swift fox den complexes on both continuous rangeland and landscapes fragmented by cropland in northwest Texas. There were no differences …
Dietary Overlap In Giant Salamanders (Dicamptodon): Applying Null Models To Resource Partitioning, Craig A. Steele, Colin Brammer
Dietary Overlap In Giant Salamanders (Dicamptodon): Applying Null Models To Resource Partitioning, Craig A. Steele, Colin Brammer
Western North American Naturalist
We examined stomach contents of preserved specimens of larval Pacific giant salamander (Dicamptodon tenebrosus) and Cope's giant salamander (D. copei) collected from sympatric and allopatric stream populations. The dietary components of these specimens were used to calculate dietary overlap between the 2 species and to determine if changes in overlap existed between sympatric and allopatric populations. To statistically test overlap values, a randomization algorithm was used to construct a simulated data matrix (i.e., null model) in order to compare observed values of dietary overlap to a distribution of overlap values from the null model. Significant levels …
Long-Term Fire History In Great Basin Sagebrush Reconstructed From Macroscopic Charcoal In Spring Sediments, Newark Valley, Nevada, Scott Mensing, Stephanie Livingston, Pat Barker
Long-Term Fire History In Great Basin Sagebrush Reconstructed From Macroscopic Charcoal In Spring Sediments, Newark Valley, Nevada, Scott Mensing, Stephanie Livingston, Pat Barker
Western North American Naturalist
We use macroscopic charcoal analysis to reconstruct fire history in sagebrush (Artemisia tridentata var. wyomingensis and A. tridentata var. tridentata), in Newark Valley, Nevada. We analyzed charcoal at continuous 1-cm intervals (~7–127 years), and pollen at 2- to 10-cm intervals (~70–263 years) in a core spanning the last 5500 cal yr BP (calendar years before present). A charcoal peak in the historic period was associated with a >1400-ha fire dated to 1986 that burned in the watershed. We reconstructed the prehistoric fire history by inferring fires from similar charcoal peaks that were significantly greater than the background charcoal …
Aspects Of Sacramento Pikeminnow Biology In Nearshore Habitats Of The Sacramento–San Joaquin Delta, California, Matthew L. Nobriga, Frederick Feyrer, Randall D. Baxter
Aspects Of Sacramento Pikeminnow Biology In Nearshore Habitats Of The Sacramento–San Joaquin Delta, California, Matthew L. Nobriga, Frederick Feyrer, Randall D. Baxter
Western North American Naturalist
We documented distribution, relative abundance, diet composition, and body condition of Sacramento pikeminnow Ptychocheilus grandis during 2001 and 2003 at 5 sites in the Sacramento–San Joaquin Delta, California. Sacramento pikeminnow densities in nearshore habitats were higher in 2003 than 2001. In both years, spatial distribution of beach seine densities was similar. There were no significant differences in density among sampling sites except for the southernmost site where the catch was near zero. Based on rotary screw-trap data from a 6th site, we found relative abundance of Sacramento pikeminnow entering the Delta via an artificial floodplain was positively correlated with flow. …
Estimating Spatial Curve Number For Hydrologic Response Analysis Of A Small Watershed
Estimating Spatial Curve Number For Hydrologic Response Analysis Of A Small Watershed
Journal of Spatial Hydrology
An approach to estimate the curve number (CN) at each pixel unit of a satellite imagery, which is a key parameter in the widely used Soil Conservation Service Curve Number (SCS- CN) hydrologic model, is proposed. Instead of mapping land use and its temporal dynamics from satellite imageries, this approach linearly unmixes the multi-spectral radiances into three fractional layers which primarily control the degree of saturation within a watershed occurring due to a 25 cm-depth storm event, i.e., physically interpreted as the CN. The fraction layers used are water, sand and pure vegetation. In order to obtain a relationship between …