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1 Univariate, multivariate, and geostatistical techniques were used to quantify the scale and degree of soil variability around individual perennial sagebrush (Artemisia tridentata ssp. vaseyana) and bluebunch wheatgrass (Pseudoroegneria spicata ssp. spicata) plants. This variability was then compared to that found across the larger sagebrush-steppe site. Samples were taken every metre in a 10-m $\times$ 12-m grid and every 12.5 cm in nine nested 0.5-m $\times$ 0.5-m grids containing at least one Artemisia shrub or Pseudoroegneria tussock (362 total samples). The 11 soil properties measured were organic matter, pH, water content, live root mass, microbial respiration, net N mineralization, nitrification potential,...
Desert plants can influence the pattern of resources in soil resulting in small-scale enriched zones. Although conceptually simple, the shape, size, and orientation of these "resource islands" are difficult to study in detail using conventional sampling regimes. To demonstrate and alternative approach, we sampled soil under and around individual Artemisia tridentata (sagebrush), a dominant shrub of cool desert environments, and analyzed the samples with univariate statistics and geostatistics. Univariate Halvorson, Jonathan J, Harvey Bolton Jr, Jeffrey L Smith, and Richard E Rossi. ?Geostatistical analysis of resource islands under Artemisia tridentata in the shrub-steppe.? Western North American Naturalist 54,...
By influencing nutrient mineralization in the soil, decomposers may affect the performance of plants and their associated herbivores. The strength of above–belowground linkages may therefore depend on the availability of nutrients in ecosystems. We investigated the dependency of decomposer- and leaf-herbivore-mediated changes in plant performance on soil nutrient availability in microcosm systems. In separate treatments, Poa annua was used as host plant for the herbivore and was grown in combination with different herb species: Plantago lanceolata, Trifolium repens, and Sanguisorba minor. At three different levels of nutrient availability, the impact of Collembola (Folsomia candida) and aphids (Rhopalosiphum padi),...
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Six large wildfires have burned in Mesa Verde National Park during the last 15 years, and extensive portions of burns were invaded by non-native plant species. The most threatening weed species include Carduus nutans, Cirsium arvense, and Bromus tectorum, and if untreated, they persist at least 13 years. We investigated patterns of weed distribution to identify plant communities most vulnerable to post-fire weed invasion and created a spatially explicit model to predict the most vulnerable sites. At the scale of the entire park, mature pi�on?juniper woodlands growing on two soil series were most vulnerable to post-fire weed invasion; mountain shrublands were the least vulnerable. At a finer scale, greater richness...
This paper discusses the important limitations in several areas of element interaction research and highlights the discrepancies between model formulations and observable ecosystem properties, including carbon dynamics in soils and element ratios and threshold effects. Some difficulties in sampling of individual species within microbial communities and in determining the flexibility of microbial stoichiometry are discussed. Also covered are the new approaches and recent advancements in element cycling research, e.g., resolving the chemical identity of element observations, element analysis for individuals and species, and scaling element interactions from sites to regions. Finally, some elements of a proposed experimental...
Soil nutrient availability influences plant invasions. Resin capsules were used to examine soil nutrient bioavailability along 2 sagebrush–grassland elevation transects in the east Tintic Range (Utah) and Shoshone Range (Nevada). In the fall of 2001, treatments were applied to 3 replicate plots at each site, which included prescribed burning, herbaceous vegetation removal, and controls. Cheatgrass (Bromus tectorum L.) was overseeded in small subplots within each treatment. Following treatments in each plot, resin capsules were installed at 15-cm depth in a shrub interspace and a B. tectorum–overseeded area. Nutrient availability was integrated during late fall to spring and spring to late fall for 2 years. Herbaceous...
Desert plants can influence the pattern of resources in soil resulting in small-scale enriched zones. Although conceptually simple, the shape, size, and orientation of these "resource islands" are difficult to study in detail using conventional sampling regimes. To demonstrate and alternative approach, we sampled soil under and around individual Artemisia tridentata (sagebrush), a dominant shrub of cool desert environments, and analyzed the samples with univariate statistics and geostatistics. Univariate statistics revealed that soil variables like total inorganic-N, soluble-C, and microbial biomass-C were distributed with highest mean values within about 25 cm of the plant axis and significantly lower mean values...
By influencing nutrient mineralization in the soil, decomposers may affect the performance of plants and their associated herbivores. The strength of above–belowground linkages may therefore depend on the availability of nutrients in ecosystems. We investigated the dependency of decomposer- and leaf-herbivore-mediated changes in plant performance on soil nutrient availability in microcosm systems. In separate treatments, Poa annua was used as host plant for the herbivore and was grown in combination with different herb species: Plantago lanceolata, Trifolium repens, and Sanguisorba minor. At three different levels of nutrient availability, the impact of Collembola (Folsomia candida) and aphids (Rhopalosiphum padi),...


    map background search result map search result map Geostatistical Patterns of Soil Heterogeneity Around Individual Perennial Plants Predicting and mitigating weed invasions to restore natural post-fire succession in Mesa Verde National Park, Colorado, USA Predicting and mitigating weed invasions to restore natural post-fire succession in Mesa Verde National Park, Colorado, USA Geostatistical Patterns of Soil Heterogeneity Around Individual Perennial Plants