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Articles 1 - 7 of 7
Full-Text Articles in Life Sciences
Isotopic Discrimination In The Double-Crested Cormorant (Phalacrocorax Auritus), Elizabeth C. Craig, Brian S. Dorr, Katie C. Hanson-Dorr, Jed P. Sparks, Paul D. Curtis
Isotopic Discrimination In The Double-Crested Cormorant (Phalacrocorax Auritus), Elizabeth C. Craig, Brian S. Dorr, Katie C. Hanson-Dorr, Jed P. Sparks, Paul D. Curtis
Brian S Dorr
The diet-tissue discrimination factor is the amount by which a consumer’s tissue varies isotopically from its diet, and is therefore a key element in models that use stable isotopes to estimate diet composition. In this study we measured discrimination factors in blood (whole blood, red blood cells and plasma), liver, muscle and feathers of Double- crested Cormorants (Phalacrocorax auritus) for stable isotope ratios of carbon, nitrogen and sulfur. Cormorants exhibited discrimination factors that differed significantly among tissue types (for carbon and nitrogen), and differed substantially (in the context of the isotopic variation among relevant prey species) from those observed in …
Rooted In Hell: Simulating Phragmites Australis, Rachel Nydegger Rozum, Jacob Duncan, James Powell Ph.D.
Rooted In Hell: Simulating Phragmites Australis, Rachel Nydegger Rozum, Jacob Duncan, James Powell Ph.D.
Rachel Nydegger Rozum
Across the estuaries of the east coast and wetlands of the Great Lakes, the invasive grass Phragmites australis outcompetes other vegetation and destroys local ecosystems. Because its roots are tolerant to salinity that other plants find hellish, Phragmites invasions begin with vegetative spread of genetic clones in brackish marshlands.This plant can grow over three meters tall at densities of 50 stems/m2, provides poor wildlife habitat, and is very difficult to eradicate. A discrete life stage model on a yearly time step captures seed survivorship in a seed bank, sexual and asexual recruitment into a juvenile age class, and differential competition …
Influence Of Simulated Double-Crested Cormorant, Phalacrocorax Auritus, Predation On Multiple-Batch Production Of Channel Catfish, Ictalurus Punctatus, Brian S. Dorr, Carole R. Engle
Influence Of Simulated Double-Crested Cormorant, Phalacrocorax Auritus, Predation On Multiple-Batch Production Of Channel Catfish, Ictalurus Punctatus, Brian S. Dorr, Carole R. Engle
Brian S Dorr
The double-crested cormorant, Phalacrocorax auritus, is considered the primary depredating bird species on commercially produced channel catfish, Ictalurus punctatus, in the southeastern USA. We simulated different levels of cormorant predation on losses at harvest and economic effects on channel catfish production in a multiple-batch cropping system. We observed significant (P<0.05) declines in catfish production at increasing levels of cormorant predation in this study. This decline was mitigated by increased individual growth of catfish at higher predation rates (i.e., lower catfish densities). This mitigating effect produced a non-linear relationship with total kg of catfish harvested per pond resulting in a non-linear incremental increase in breakeven price related to predation. Costs of production ($/kg) increased with increasing predation levels up to very high levels of predation with a cumulative maximum increase in breakeven price of $0.143/kg. These results indicate that losses at harvest due to cormorant predation occur immediately but are mitigated in part by compensatory growth of individual catfish. Losses due to cormorant predation in multi-batch systems can be considerable, but there is not a 1:1 relationship between losses and kg of catfish harvested due to compensatory actors.
Influence Of Current Land Use And Edaphic Factors On Arbuscular Mycorrhizal (Am) Hyphal Abundance And Soil Organic Matter In And Near Serengeti National Park, Geofrey Soka, Mark Ritchie, Emilian Mayemba
Influence Of Current Land Use And Edaphic Factors On Arbuscular Mycorrhizal (Am) Hyphal Abundance And Soil Organic Matter In And Near Serengeti National Park, Geofrey Soka, Mark Ritchie, Emilian Mayemba
Geofrey Soka
Arbuscular mycorrhizal fungi (AMF) are important microbial symbionts for plants especially when soil phosphorus (P) and nitrogen (N) are limited. Little is known about the distribution of AM hyphae in natural systems of tropical soils across landscapes and their association with different land uses. We studied mycorrhizal hyphal abundance in a wildlife grazed system, a livestock grazed system and under cultivated soils in and near Serengeti National Park, Tanzania. Samples of the upper 15 cm of soil beneath locally dominant plant species were collected. Hyphae were preserved on permanent slides and the length of hyphae per cubic centimeter of soil …
Impacts Of Colonial Waterbirds On Vegetation And Potential Restoration Of Island Habitats, Christopher R. Ayers, Katie C. Hanson-Dorr, Sadie O'Dell, Charles D. Lovell, Michael L. Jones, Jason R. Suckow, Brian S. Dorr
Impacts Of Colonial Waterbirds On Vegetation And Potential Restoration Of Island Habitats, Christopher R. Ayers, Katie C. Hanson-Dorr, Sadie O'Dell, Charles D. Lovell, Michael L. Jones, Jason R. Suckow, Brian S. Dorr
Brian S Dorr
Colonial waterbirds have impacted forested island ecosystems throughout their breeding range, changing vegetation, and soil characteristics and bird communities.Our objectives were to (1) determine effects of three levels of colonial waterbird exclusion on overall vegetation diversity and growth, and survival of a candidate restoration species (black elderberry; Sambucus nigra canadensis); (2) investigate effects of different planting techniques on survival and growth of black elderberry; and (3) determine effects of waterbird colonization on soil chemistry. In 2012, we investigated effects of three levels of waterbird exclusion (none control plots [CON]; partial, which excluded waterbirds larger than gulls [PEX]; and full which …
Slotted Drainage Pipe For Sub-Irrigation, David A. Bainbridge
Slotted Drainage Pipe For Sub-Irrigation, David A. Bainbridge
David A Bainbridge
Subirrigation with drainage pipe was effective for planting a windbreak in the Mojave Desert. The pipe was refilled periodically with a water truck. Survival was very good.
Preliminary Home Range Study Of Juvenile Chinese Horseshoe Crabs, Tachypleus Tridentatus (Xiphosura), Using Passive Tracking Methods, Kit Yue Kwan, Pks Shin, Sg Cheung
Preliminary Home Range Study Of Juvenile Chinese Horseshoe Crabs, Tachypleus Tridentatus (Xiphosura), Using Passive Tracking Methods, Kit Yue Kwan, Pks Shin, Sg Cheung
KWAN Kit Yue, Billy
Three passive tracking methods, using colored plastic tag (CPT), passive integrated transponder (PIT) tag, and CPT plus PIT were compared to track the movements of juvenile Chinese horseshoe crabs, Tachypleus tridentatus, in summer 2013 on a mudflat in Hong Kong. The study site was re-visited within 2 months after the release of the tagged individuals on ten occasions during low tides. The cumulative recovery rates of the tagged juveniles ranged from 70 to 82 %, with the number of position fixes where each individual was recovered during the repeated field visits varying from one to seven. Based on the adaptive …