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Ecology

Effects of nutrient patches and root systems on the clonal plasticity of a rhizomatous grass

Effects of nutrient patches and root systems on the clonal plasticity of a rhizomatous grass Elisabeth Huber-Sannwald INTRODUCTION Horizontal expansion and exploratory growth of rhizomes expose individual clones to spatial variation in their habitats (Snaydon 1962). Environmental variation in a plant community consists of both the heterogeneous distribution of abiotic resources such as water, nutrients, […]

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Ecology

The stable nitrogens isotope ratio as a marker of food-web interactions and fish migration

The stable nitrogens isotope ratio as a marker of food-web interactions and fish migration Sture Hansson INTRODUCTION For several years, we have studied trophic interactions in a coastal area of the northern Baltic proper, and based on gut analyses we can describe the foodweb structure of dominant ecological groups [ILLUSTRATION FOR FIGURE 1 OMITTED]. Our […]

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Ecology

Power analysis for detecting trends in the presence of concomitant variables

Power analysis for detecting trends in the presence of concomitant variables David M. Nickerson INTRODUCTION Wildlife management often requires the detection of trends in abundance over time, after adjusting survey counts for concomitant variables that are known to affect observability (e.g., rainfall, temperature, etc.). Here, as in Gerrodette (1987, 1991) and Link and Hatfield (1990), […]

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Ecology

Consequence for plantain chemistry and growth when herbivores are attacked by predators

Consequence for plantain chemistry and growth when herbivores are attacked by predators Nancy E. Stamp INTRODUCTION Whether, and if so how, the presence of natural enemies alters the impact of insect herbivores on their host plants remains a central issue in understanding tritrophic-level interactions in natural and managed ecosystems (Price et al. 1980). More specifically, […]

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Ecology

Herbivore effects on plant species density at varying productivity levels

Herbivore effects on plant species density at varying productivity levels Laura Gough INTRODUCTION The relationship between biomass and species density (the number of species per unit area) is described as a hump-shaped curve, with a peak in species density at a low to intermediate level of biomass (Grime 1973). This pattern has been found by […]

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Ecology

Origin of a park-forest vegetation mosaic in the Wind River Range, Wyoming

Origin of a park-forest vegetation mosaic in the Wind River Range, Wyoming Elizabeth A. Lynch INTRODUCTION Throughout the Rocky Mountains, the vegetation of the montane and subalpine zones is composed of a mixture of conifer forests and treeless areas dominated by grasses and sagebrush (Artemisia spp.) called “parks.” While some parks are located in valley […]

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Ecology

Phenotypic plasticity in foraging behavior of sawfly larvae

Phenotypic plasticity in foraging behavior of sawfly larvae Antti Kause INTRODUCTION Phenotypic plasticity, an ability of a genotype to express different phenotypes in response to different environments, may be adaptive or purely environmentally constrained. Despite some debate in the literature (Via 1993), plasticity studies have proven to be an efficient approach for understanding the causes […]

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Ecology

An 840-year record of fire and vegetation in a boreal white spruce forest

An 840-year record of fire and vegetation in a boreal white spruce forest C.P.S. Larsen INTRODUCTION Fire and climate are key processes that control boreal forest vegetation dynamics (Shugart et al. 1992). Fire frequency in the boreal forest has been studied using historical and dendrochronological records (Johnson 1992). Postfire vegetation dynamics have been studied using […]

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Ecology

Interannual variation in greater flamingo breeding success in relation to water levels

Interannual variation in greater flamingo breeding success in relation to water levels Frank Cezilly INTRODUCTION In most wetlands, fluctuations in water depth appear to influence breeding success of waterbirds (Ogden et al. 1980, Frederick and Collopy 1989, Bildstein et al. 1990, Hafner et al. 1994) by strongly affecting food availability. Reduced breeding, or even abstinence […]

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Ecology

Plant hybrid zones and insect host range expansion

Plant hybrid zones and insect host range expansion – Hybridization and Resistance to Parasites Diana Pilson INTRODUCTION Most herbivorous insects are specialized to some degree (Price 1980, Fox and Morrow 1981, Strong et al. 1984). Some species feed on hosts in just a few families or genera, while others are extreme specialists and feed on […]