Effects of spatial habitat heterogeneity on habitat selection and annual fecundity for a migratory forest songbird   总被引：1，自引：1，他引：0  

Kerri L. Cornell  Therese M. Donovan 《Landscape Ecology》2010,25(1):109-122

Understanding how spatial habitat patterns influence abundance and dynamics of animal populations is a primary goal in landscape ecology. We used an information-theoretic approach to investigate the association between habitat patterns at multiple spatial scales and demographic patterns for black-throated blue warblers (Dendroica caerulescens) at 20 study sites in west-central Vermont, USA from 2002 to 2005. Sites were characterized by: (1) territory-scale shrub density, (2) patch-scale shrub density occurring within 25 ha of territories, and (3) landscape-scale habitat patterns occurring within 5 km radius extents of territories. We considered multiple population parameters including abundance, age ratios, and annual fecundity. Territory-scale shrub density was most important for determining abundance and age ratios, but landscape-scale habitat structure strongly influenced reproductive output. Sites with higher territory-scale shrub density had higher abundance, and were more likely to be occupied by older, more experienced individuals compared to sites with lower shrub density. However, annual fecundity was higher on sites located in contiguously forested landscapes where shrub density was lower than the fragmented sites. Further, effects of habitat pattern at one spatial scale depended on habitat conditions at different scales. For example, abundance increased with increasing territory-scale shrub density, but this effect was much stronger in fragmented landscapes than in contiguously forested landscapes. These results suggest that habitat pattern at different spatial scales affect demographic parameters in different ways, and that effects of habitat patterns at one spatial scale depends on habitat conditions at other scales.  相似文献   

Area‐wide management of Aedes albopictus. Part 2: Gauging the efficacy of traditional integrated pest control measures against urban container mosquitoes     

Dina M Fonseca  Isik Unlu  Taryn Crepeau  Ary Farajollahi  Sean P Healy  Kristen Bartlett‐Healy  Daniel Strickman  Randy Gaugler  George Hamilton  Daniel Kline  Gary G Clark 《Pest management science》2013,69(12):1351-1361

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Optimization of hydrolytic and oxidative enzyme methods for ecosystem studies     

Donovan P. German  Michael N. Weintraub  Christian L. Lauber  Steven D. Allison 《Soil biology & biochemistry》2011,43(7):1387-1397

Microbial digestive enzymes in soil and litter have been studied for over a half century, yet the understanding of microbial enzymes as drivers of ecosystem processes remains hindered by methodological differences among researchers and laboratories. Modern techniques enable the comparison of enzyme activities from different sites and experiments, but most researchers do not optimize enzyme assay methods for their study sites, and thus may not properly assay potential enzyme activity. In this review, we characterize important procedural details of enzyme assays, and define the steps necessary to properly assay potential enzyme activities in environmental samples. We make the following recommendations to investigators measuring soil enzyme activities: 1) run enzyme assays at the environmental pH and temperature; 2) run proper standards, and if using fluorescent substrates with NaOH addition, use a standard time of 1 min between the addition of NaOH and reading in a fluorometer; 3) run enzyme assays under saturating substrate concentrations to ensure V_max is being measured; 4) confirm that product is produced linearly over the duration of the assay; 5) examine whether mixing during the reaction is necessary to properly measure enzyme activity; 6) find the balance between dilution of soil homogenate and assay variation; and 7) ensure that enzyme activity values are properly calculated. These steps should help develop a unified understanding of enzyme activities in ecosystem ecology.  相似文献   

Parent's responses to nutrient claims and sports celebrity endorsements on energy-dense and nutrient-poor foods: an experimental study     

Dixon H  Scully M  Wakefield M  Kelly B  Chapman K  Donovan R 《Public health nutrition》2011,14(6):1071-1079

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Dietary strategies to improve the iron and zinc nutriture of young women following a vegetarian diet     

Gibson  R. S.  Donovan  U. M.  Heath  A-L. M. 《Plant foods for human nutrition (Dordrecht, Netherlands)》1997,51(1):1-16

Dietary strategies to enhance the content and bioavailability of iron and zinc in vegetarian diets were compiled. Strategies included increasing promoters and decreasing antagonists of iron and zinc absorption, adopting food preparation and processing methods which hydrolyze the phytate content of cereals and legumes, and using iron cookware. These strategies were used to devise two vegetarian menus based on food consumption patterns derived from three day weighed food records of 78 Canadian lacto-ovo-vegetarian adolescents. The iron and zinc, as well as calcium, phosphorus, thiamin, riboflavin, niacin, vitamin A, protein and energy content of the devised menus were all higher than the actual intakes and the corresponding Canadian recommended nutrient intakes. Results show the overall nutrient adequacy of the recommended vegetarian menus and indicate that young lacto-vegetarian women can potentially meet their estimated dietary requirements for absorbed iron and zinc through modest modifications to the diet. Laboratory studies designed to measure the total amount of iron and zinc absorbed from these diets by young vegetarian women are needed to verify the efficacy of the devised menus.  相似文献   

An investigation into the grazing efficiency of perennial ryegrass varieties     

Tomas Tubritt  Luc Delaby  Trevor Gilliland  Michael O’Donovan 《Grass and Forage Science》2020,75(3):253-265

The objective of this study was to compare the grazing efficiency of 30 perennial ryegrass varieties, differing in ploidy and heading date. Plots were grazed by lactating dairy cows and managed under a rotational grazing system with 19 grazing events occurring over two years. Pre-grazing and post-grazing compressed sward heights were measured with a rising plate meter. A mixed model was used to predict the post-grazing sward height of each variety based on year, grazing event, block and pre-grazing sward height. Residual grazed height (RGH) was derived as the difference between the actual and predicted post-grazing sward height and was used as the measure of grazing efficiency. Negative RGH values indicated that the actual herbage removed was greater than that predicted and so indicated a superior grazing efficiency. Varieties differed in their level of grazing efficiency (p < .001), with RGH values ranging from −0.38 to +0.34 cm. Tetraploid varieties exhibited significantly greater grazing efficiency performance than diploids (p < .001), with average RGH values of −0.13 and +0.13 cm respectively. A significant difference in grazing efficiency was found among recommended perennial ryegrass varieties that are not being recorded by mechanically harvested simulated grazing protocols. A variety reappraisal that included grazing efficiency could identify varieties capable of improving on-farm livestock productivity from grass.  相似文献   

Boots on the ground: construction management of urbanizing irrigated farm land     

Donovan Neese  Ed Gerak  Walt Cooper 《Irrigation and Drainage Systems》2009,23(2-3):131-139

Since its inception, in 1885 the Buckeye Irrigation Canal has delivered irrigation water in the Buckeye Valley, southwest of Phoenix, Arizona. Throughout its tenure the owners of the canal have consulted design professionals for its engineering needs. Early engineering in 1885 established canal alignments, delivery points and channel capacity. Until recently, the Buckeye Valley was a rural area relying on agricultural revenues to drive the local economy. Now, due to the recent housing market boom new homes started springing up like corn in September driving the existing open-channel laterals below grade into a patch work redesigned pipeline system. Because of these changes, professional construction managers are an enormous benefit to the Buckeye Water Conservation and Drainage District (BWCDD), the owner of the canal.As a result of this urbanization, contractors working for home developers are installing irrigation pipelines and systems with the focus of completing the project as quickly and economically as possible. Irrigation providers, on the other hand, focus on meeting the agricultural needs of their clients with consistent and uninterrupted water delivery. The services of a professional construction manager help both entities achieve their respective goals, shield BWCDD from construction of sub-par systems and risk, maintain uninterrupted service to growers and providing the technical expertise to communicate with both BWCDD and contractors.Construction managers provide a number of services to rural irrigation districts under-going urbanization. They team with an irrigation district by:

• Understanding irrigation design concepts;
• Understanding agricultural demands;
• Providing a thorough knowledge of construction practices and standards;
• Creating long-term design functionality;
• Reducing stress on and increasing productivity of personnel;
• Coordinating construction activities with water deliveries;
• Verifying constructed facilities perform as designed, which reduces maintenance costs.

Construction managers represent an irrigation district in the field by:

• Reviewing development plans for adherence to current construction standards and practices and coordinates construction schedules with water delivery needs;
• Observing construction for proper installation;
• Clarifying installers understanding of plans and specifications;
• Coordinating interruptions in service;
• Tracking multiple construction projects;
• Explaining agricultural practices to contractor personnel;
• Providing a single point of contact for construction related correspondence.

These “boots on the ground” create a local presence with a focus on the specific needs unique to an irrigation district. They provide a liaison while minimizing the impact to its growers.This paper will discuss the strain of urbanization on an irrigation district and the benefits of an engineering consulting firm to manage construction projects. The benefits include expertise, technical resources, design capability, coordination and inspection. Construction managers can help protect an irrigation district from being overwhelmed by rapid urbanization.  相似文献   

Monocyte function in rhesus monkeys with simian acquired immune deficiency syndrome   总被引：1，自引：0，他引：1  

E K Legrand  R M Donovan  P A Marx  J E Moulton  A T Cheung  A E Lewis  M B Gardner 《Veterinary immunology and immunopathology》1985,10(2-3):131-146

Monocyte function in rhesus monkeys with simian acquired immune deficiency syndrome (SAIDS) was compared with that in age-matched normal juvenile rhesus monkeys. The functional tests were 1) chemotaxis, 2) phagocytosis of opsonized Candida albicans, 3) killing and/or growth inhibition of Candida albicans, 4) generation of respiratory burst, and 5) monocyte-derived macrophage response (morphology and/or respiratory burst) to stimulating agents such as lymphokines, gamma interferon, endotoxin, and phorbol myristate acetate. The monkeys tested had either clinical SAIDS (alive with lymphadenopathy, splenomegaly, and lymphopenia or neutropenia) or had terminal SAIDS (moribund due to the disease). Responses of monocytes from 14 monkeys with clinical SAIDS were indistinguishable from those of 9 normal juvenile rhesus monkeys, whereas monocytes from 3 monkeys with terminal SAIDS had enhanced phagocytosis and respiratory burst capacity. Chemotaxis, candidacidal/stasis activity, and response to stimulating agents were normal in these terminal cases. Plasma from the SAIDS monkeys was as capable of opsonizing yeasts and of being able to generate chemotactic factors by endotoxin as was control plasma. SAIDS retrovirus (SRV) was detected by co-cultivation of pure monocyte-derived macrophage cultures with Raji cells, an indicator cell line which forms syncytia in the presence of SRV. Four terminal SAIDS cases and one late-stage clinical SAIDS case were virus-positive when the number of macrophages in the cultures ranged from less than 50 to about 500. Terminal SAIDS monocyte-derived macrophages in culture as long as 17 days produced SRV. These data show that in monkeys with SAIDS the major effector functions of monocytes and macrophages involved in host defense are intact (even up until death). Additionally, some of the monocytes are productively infected, and these infected monocytes are viable and adherent in culture.  相似文献   

Quercus species differ in water and nutrient characteristics in a resource-limited fall-line sandhill habitat     

Donovan LA  West JB  McLeod KW 《Tree physiology》2000,20(14):929-936

We compared co-occurring mature Quercus laevis Walt. (turkey oak), Q. margaretta Ashe (sand post oak) and Q. incana Bartr. (bluejack oak) trees growing in resource-limited sandhill habitats of the southeastern United States for water and nutrient characteristics. The Quercus spp. differed in their distribution along soil water and nutrient gradients, and in their access to and use of water, even though the study year was wetter than average with no mid-season drought. Quercus laevis had the greatest access to soil water (least negative pre-dawn water potential, psi(pd)) and the most conservative water-use strategy based on its relatively low stomatal conductance (g(s)), high instantaneous water-use efficiency (WUE), least negative midday water potential (psy(md)) and high leaf specific hydraulic conductance (K(L)). Quercus margaretta had the least conservative water-use characteristics, exhibiting relatively high g(s), low instantaneous WUE, most negative psi(md), and low K(L). Quercus margaretta also had a low photosynthetic nitrogen-use efficiency (PNUE), but a high leaf phosphorus concentration. Quercus incana had the poorest access to soil water, but intermediate water-use characteristics and leaf nutrient characteristics more similar to those of Q. laevis. There were no species differences for photosynthesis (A), leaf nitrogen on an area basis, or seasonally integrated WUE (delta13C). Both A and g(s) were positively correlated for each species, but A and g(s) were generally not correlated with psi(pd), psi(md) or delta psi(pd-md). Although we found differences in resource use and resource status among these sandhill Quercus spp., the results are consistent with the interpretation that they are generally drought avoiders. Quercus laevis may have an advantage on xeric ridges because of its greater ability to access soil water and use it more conservatively compared with the other Quercus spp.  相似文献   

Stomatal sensitivity to vapor pressure deficit and its relationship to hydraulic conductance in Pinus palustris     

Addington RN  Mitchell RJ  Oren R  Donovan LA 《Tree physiology》2004,24(5):561-569

We studied the response of stomatal conductance at leaf (gS) and canopy (GS) scales to increasing vapor pressure deficit (D) in mature Pinus palustris Mill. (longleaf pine) growing in a sandhill habitat in the coastal plain of the southeastern USA. Specifically, we determined if variation in the stomatal response to D was related to variation in hydraulic conductance along the soil-to-leaf pathway (KL) over the course of a growing season. Reductions in KL were associated with a severe growing season drought that significantly reduced soil water content (theta) in the upper 90-cm soil profile. Although KL recovered partially following the drought, it never reached pre-drought values. Stomatal sensitivity to D was well correlated with maximum gS at low D at both leaf and canopy scales, and KL appeared to influence this response by controlling maximum gS. Our results are consistent with the hypothesis that stomatal response to D occurs to regulate minimum leaf water potential, and that the sensitivity of this response is related to changes in whole-plant hydraulics.  相似文献