Soil microbial community response to nitrogen enrichment in two scrub oak forests     

Jennifer Adams Krumins  John Dighton  Dennis Gray  Rima B. Franklin  Peter J. Morin  Michael S. Roberts 《Forest Ecology and Management》2009,258(7):1383-1390

Microbial communities play a pivotal role in soil nutrient cycling, which is affected by nitrogen loading on soil fungi and particularly mycorrhizal fungi. In this experiment, we evaluated the effects of allochthonous nitrogen addition on soil bacteria and fungi in two geographically distinct but structurally similar scrub oak forests, one in Florida (FL) and one in New Jersey (NJ). We applied allochthonous nitrogen as aqueous NH₄NO₃ in three concentrations (0 kg ha⁻¹ yr⁻¹ (deionized water control), 35 kg ha⁻¹ yr⁻¹ and 70 kg ha⁻¹ yr⁻¹) via monthly treatments over the course of 1 yr. We applied treatments to replicated 1 m² plots, each at the base of a reference scrub oak tree (Quercus myrtifolia in FL and Q. ilicifolia in NJ). We measured microbial community response by monitoring: bacterial and fungal biomass using substrate induced respiration, and several indicators of community composition, including colony and ectomycorrhizal morphotyping and molecular profiling using terminal restriction fragment length polymorphism (TRFLP). Bacterial colony type richness responded differently to nitrogen treatment in the different sites, but ectomycorrhizal morphotype richness was not affected by nitrogen or location. Both experimental sites were dominated by fungi, and FL consistently supported more bacterial and fungal biomass than NJ. Bacterial biomass responded to nitrogen addition, but only in FL. Fungal biomass did not respond significantly to nitrogen addition at either experimental site. The composition of the bacterial community differed between nitrogen treatments and experimental sites, while the composition of the fungal community did not. Our results imply that bacterial communities may be more sensitive than fungi to intense pulses of nitrogen in sandy soils.  相似文献   

Climate change effects on historical range and variability of two large landscapes in western Montana,USA     

Robert E. Keane  Lisa M. HolsingerRussell A. Parsons  Kathy Gray 《Forest Ecology and Management》2008

Quantifying the historical range and variability of landscape composition and structure using simulation modeling is becoming an important means of assessing current landscape condition and prioritizing landscapes for ecosystem restoration. However, most simulated time series are generated using static climate conditions which fail to account for the predicted major changes in future climate. This paper presents a simulation study that generates reference landscape compositions for all combinations of three climate scenarios (warm-wet, hot-dry, and current) and three fire regime scenarios (half historical, historical, and double historical fire frequencies) to determine if future climate change has an effect on landscape dynamics. We applied the spatially explicit, state-and-transition, landscape fire succession model LANDSUM to two large landscapes in west-central Montana, USA. LANDSUM was parameterized and initialized using spatial data generated from the LANDFIRE prototype project. Biophysical settings, critical spatial inputs to LANDSUM, were empirically modeled across the landscape using environmental gradients created from historical and modeled future climate daily weather data summaries. Successional pathways and disturbance probabilities were assigned to these biophysical settings based on existing field data and extensive literature reviews. To assess the impact of changes in climate and fire regime, we compared simulated area burned and landscape composition over time among the different simulation scenario combinations using response variables of Sorenson's index (a global measure of similarity) and area occupied by the dominant vegetation class (simple indicator of change in landscape composition). Results show that simulated time series using future predicted climate scenarios are significantly different from the simulated historical time series and any changes in the fire regime tend to create more dissimilar and more variable simulated time series. Our study results indicate that historical time series should be used in conjunction with simulated future time series as references for managing landscapes.  相似文献   

Femoral head ostectomy for the treatment of acetabular fracture and coxofemoral joint luxation in a Potbelly pig          下载免费PDF全文

Joe S. Smith  Munashe Chigerwe  Carly Kanipe  Sarah Gray 《Veterinary surgery : VS》2017,46(2):316-321

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Quantifying the sources of epistemic uncertainty in model predictions of insect disturbances in an uncertain climate     

David R. Gray 《Annals of Forest Science》2017,74(3):48

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SPORE series winner. Immunology for clinicians: a "Trojan Horse" approach     

Gray CM  Loubser S  Kriel C  Mercer M  Brookes H 《Science (New York, N.Y.)》2010,329(5999):1613-1614

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Nitrogen fertilization and aspects of fruit yield in a Missouri black walnut alley cropping practice     

Dean Gray  H. E. Gene Garrett 《Agroforestry Systems》1998,44(2-3):333-344

Increasing nut production through cultural practices is important to landowners for maximizing economic gain from agroforestry plantings. This project studied the effects of applying low rates of nitrogen (N) fertilizer during either the spring or late summer, on pistillate flowers formed, fruits retained, and fruit quality (percentage kernel) in black walnut (Juglans nigra L.) grown under alley cropping management. Treatments consisted of two forms of nitrogen fertilizers (NH₄NO₃ and NaNO₃) applied in mid-April, or mid-August of 1995 and 1996, and a nonfertilized control group. Pistillate flowers counted in May, 1996, showed that fertilized trees, regardless of timing or form of N applied, produced from 2.3 to 3.4 times the number of pistillate flowers as unfertilized control trees. Through the season, the fertilized trees had greater fruit retention, and ended with 2.9 to 4.8 times more walnuts (on a whole tree basis) than nonfertilized control trees. In addition, all fertilizer treatments resulted in increased nut yields from 1995 to 1996, while unfertilized control tree yields decreased approximately 70%. Summer application of fertilizer showed the greatest benefit to kernel weight. Average kernel weights of nuts from the summer-fertilized trees increased from 1995 to 1996, while kernel weight averages from spring-fertilized and nonfertilized trees remained unchanged or decreased. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

Evaluation of observer‐ and industry‐based catch data in a recreational charter fishery          下载免费PDF全文

C. A. Gray  S. J. Kennelly 《Fisheries Management and Ecology》2017,24(2):126-138

There is international recognition for greater inclusion of recreational fisheries catch data in species, fisheries and ecosystem assessments. Recreational charter fisheries provide important social services and contribute to total species catches. This study compares and validates industry logbook catch and effort data (1,357 trips) against observer data (154 trips) across six ports in a recreational charter fishery in eastern Australia. The mean numbers of clients and fishing effort (hours) per trip varied inconsistently between data sources and among ports. Logbooks did not adequately report released catches, and the mean number of species retained per trip was consistently underestimated in logbooks compared to observer data. For both data sources, catch rates of total individuals and key species displayed similar trends across different units of effort; catch per hour, client, client/hour and trip. The mean catch rates of total individuals and most key species, except those retained for bait, were similar across data sources, as were estimates of total fleet harvests. The length compositions of retained catches of some key species displayed truncation of larger organisms in the observer data whereas other species did not. Despite the shortcomings of the logbook data, future fishery and species monitoring strategies could include industry and observer data sources.  相似文献   

Accessibility of Starch Granules to Fatty Acyl Amides     

Jonathan A. Gray  James N. BeMiller 《Cereal Chemistry》2001,78(3):236-242

Microscopic techniques were used to determine accessible regions in various starches under different swelling conditions. Fatty acyl chlorides of increasing chain length (C₆–C₁₆) were reacted with 2‐aminopyridine to produce the corresponding fatty acyl amides. Starch granules (common corn, waxy maize, potato) were treated with the series of fluorescent amides under a variety of conditions: anhydrous (hot pyridine), aqueous (no heat), and aqueous alkali (49°C, with and without swelling‐inhibiting salts). Isolated granules were then viewed by confocal laser scanning microscopy to determine reagent analog penetration. All populations of granules were heterogeneous with respect to fatty acyl amide penetration, but general patterns could be discerned. Observations also indicated that the area surrounding the hilum was more easily penetrated than was the rest of the granule matrix. No substantial differences in penetration of the fluorescent fatty acyl amides as the chain length increased (C₆–C₁₆ was observed in hot pyridine‐swollen common corn starch granules. Common corn and potato starch granules swollen in room temperature water showed cutoffs for granular exclusion at C₁₄ and C₁₂, respectively. Common corn, waxy maize, and potato starch granules treated under industrial etherification conditions (heat, pH ≈ 11, swelling‐inhibiting salts) were less accessible to C₆, C₈, and C₁₀ fluorescent amides when sodium citrate was present than when sodium sulfate was used, and less accessible in either case than in water alone or in hot anhydrous pyridine. However, appreciable differences between inhibition by sodium sulfate and sodium citrate were not observed in every case.  相似文献   

Maintenance of Contraction of Embryonic Chick Hearts in Vitro     

Gray JC  Powell EW 《Science (New York, N.Y.)》1952,116(3009):232-233

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The Language of Science     

Gray P  Buzzati-Traverso AA 《Science (New York, N.Y.)》1952,115(2986):319

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