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101.
Hanson PJ Samuelson LJ Wullschleger SD Tabberer TA Edwards GS 《Tree physiology》1994,14(12):1351-1366
Extrapolation of the effects of ozone on seedlings to large trees and forest stands is a common objective of current assessment activities, but few studies have examined whether seedlings are useful surrogates for understanding how mature trees respond to ozone. This two-year study utilized a replicated open-top chamber facility to test the effects of subambient, ambient and twice ambient ozone concentrations on light-saturated net photosynthesis (P(max)) and leaf conductance (g(l)) of leaves from mature trees and genetically related seedlings of northern red oak (Quercus rubra L.). Gas exchange measurements were collected four times during the 1992 and 1993 growing seasons. Both P(max) and g(l) of all foliage followed normal seasonal patterns of ontogeny, but mature tree foliage had greater P(max) and g(l) than seedling foliage at physiological maturity. At the end of the growing season, P(max) and g(l) of the mature tree foliage exposed to ambient ( approximately 80-100 ppm-h) and twice ambient ( approximately 150-190 ppm-h) exposures of ozone were reduced 25 and 50%, respectively, compared with the values for foliage in the subambient ozone treatment ( approximately 35 ppm-h). In seedling leaves, P(max) and g(l) were less affected by ozone exposure than in mature leaves. Extrapolations of the results of seedling exposure studies to foliar responses of mature forests without considering differences in foliar anatomy and stomatal response between juvenile and mature foliage may introduce large errors into projections of the response of mature trees to ozone. 相似文献
102.
Singsaas EL Laporte MM Shi JZ Monson RK Bowling DR Johnson K Lerdau M Jasentuliytana A Sharkey TD 《Tree physiology》1999,19(14):917-924
Because the rate of isoprene (2-methyl-1,3-butadiene) emission from plants is highly temperature-dependent, we investigated natural fluctuations in leaf temperature and effects of rapid temperature change on isoprene emission of red oak (Quercus rubra L.) leaves at the top of the canopy at Harvard Forest. Throughout the day, leaves often reached temperatures as much as 15 degrees C above air temperature. The highest temperatures were reached for only a few seconds at a time. We compared isoprene emission rates measured when leaf temperature was changed rapidly with those measured when temperature was changed slowly. In all cases, isoprene emission rate increased with increasing leaf temperature up to about 32 degrees C and then decreased with higher temperatures. The temperature at which isoprene emission rates began to decrease depended on how quickly measurements were made. Isoprene emission rates peaked at 32.5 degrees C when measured hourly, whereas rates peaked at 39 degrees C when measurements were made every four minutes. This behavior reflected the rapid increase in isoprene emission rate that occurred immediately after an increase in leaf temperature, and the subsequent decrease in isoprene emission rate when leaf temperature was held steady for longer than 20 minutes. We concluded that the observed temperature response of isoprene emission rate is a function of measurement protocol. Omitting this parameter from isoprene emission models will not affect simulated isoprene emission rates at mild temperatures, but can increase isoprene emission rates at high temperatures. 相似文献
103.
Eric L. Hyman 《Agroforestry Systems》1983,1(3):225-243
Following the model of a credit program for pulpwood production and agroforestry by smallholders in another region of the Philippines, the World Bank financed a similar scheme to produce fuelwood for the small-scale tobacco-curing industry in the Ilocos region. This project proved to be unsuccessful due to local cultural attitudes toward borrowing money, inadequate forestry extension services, and the dispersed characteristics of the fuelwood market. 相似文献
104.
Cynthia G. Locasio B. G. Lockaby Jon P. Caulfield M. Boyd Edwards M. Keith Causey 《New Forests》1990,4(4):261-269
Diversity of understory vegetation was compared among four intensities of site preparation and an adjacent 50-year-old pine-hardwood forest. The study site was a six-year-old loblolly pine (Pines taeda) plantation in the lower Piedmont of Georgia. Species richness and Shannon diversity indices were used to evaluate vine and woody (trees and shrubs) species diversity. Biomass distribution was compared among four plant categories: vines, forbs, grasses, and woody. Moderate intensity treatments (chainsaw and shear and chop) consistently ranked highest overall in diversity, with the mature pine-hardwood forest ranking lowest. Distribution of the four plant categories was not significantly affected by intensity of site preparation.Alabama Agricultural Experiment Station Series No. 9-892325P. 相似文献
105.
The potential for traditional and local ecological knowledge to contribute to biodiversity conservation has been widely recognized, but the actual application of this knowledge to biodiversity conservation is not easy. This paper synthesizes literature about traditional and local ecological knowledge and forest management in the Pacific Northwest to evaluate what is needed to accomplish this goal. We address three topics: (1) views and values people have relating to biodiversity; (2) the resource use and management practices of local forest users, and their effects on biodiversity; (3) models for integrating traditional and local ecological knowledge into biodiversity conservation on public and private lands. We focus on the ecological knowledge of forest users belonging to three groups who inhabit the region: American Indians, family forest owners, and commercial nontimber forest product harvesters. 相似文献
106.
Nontimber forest product harvesting in the Pacific Northwest is neither a new activity nor a disappearing relic of the pre-industrial era. Though the emphasis may have shifted from subsistence to commercial and recreational pursuits, harvesting and harvesters of wild species are still widespread throughout the region. Hundreds of businesses and thousands of harvesters earn part or all of their income from the harvests. Every year thousands of pounds and hundreds of nontimber forest products valued in the hundreds of millions of dollars are harvested from regional public and private forests. This harvesting of a large diversity of species represents a considerable subset of the overall terrestrial biodiversity in Pacific Northwest forests. Despite widespread extraction, little investment in research, planning, or basic inventorying and monitoring has been done on nontimber forest products. Without better information, land managers will be increasingly unable to make informed decisions on how to manage nontimber forest product biodiversity sustainably as demand for products increases. 相似文献
107.
108.
Objectives
To report our experience with thoracoscopic lung lobectomy in dogs with primary lung tumors and compare the long‐term outcome between dogs with primary lung tumors treated with lobectomy via thoracoscopy or thoracotomy.Study Design
Retrospective case series; case–control study.Animals
Thirteen dogs with primary lung tumors treated with thoracoscopic lung lobectomy; case‐matched cohort of 9 dogs with primary lung tumors treated with lobectomy via thoracotomy.Methods
Medical records from dogs that underwent thoracoscopic lung lobectomy at a single institution were reviewed. Only cases with primary lung tumors were included. Surgical complications and conversion rate were reported. Cases without conversion and with clean margins on histologic examination were matched on prognostic criteria to cases with primary lung tumors treated with lobectomy via thoracotomy. Survival was compared between thoracoscopy and thoracotomy.Results
Thirteen dogs with primary lung tumors that measured 2.2–7 cm underwent thoracoscopic lung lobectomy. Nine dogs were diagnosed with carcinoma and 4 with histiocytic sarcoma. There were 3 conversions to open thoracotomy because of poor visualization. There were no differences in short‐term outcome between dogs that had their procedures completed via thoracoscopy and those that were converted to thoracotomy. Nine dogs with clean margins were matched with 9 dogs treated via thoracotomy. Mean (standard deviation) followup was 367 (327) days for dogs undergoing thoracoscopy and 603 (612) days for dogs undergoing thoracotomy. The 2‐year survival rate was 44% for thoracoscopy and 56% for thoracotomy (P = .942).Conclusion
Selected primary lung tumors in dogs can be safely resected with thoracoscopy and not affect long‐term outcome.109.
110.
Factors affecting urine reagent strip blood results in dogs and nonhuman primates and interpretation of urinalysis in preclinical toxicology studies: a Multi‐Institution Contract Research Organization and BioPharmaceutical Company Perspective 下载免费PDF全文