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排序方式: 共有194条查询结果,搜索用时 15 毫秒
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Pekka E. Kauppi Aapo Rautiainen Kari T. Korhonen Aleksi Lehtonen Jari Liski Pekka Nöjd Sakari Tuominen Markus Haakana Tarmo Virtanen 《Forest Ecology and Management》2010,259(7):1239-1244
The growing stock more than doubled from 1.6 to 3.4 million m3 between 1912 and 2005 in forests on an area of 387 km2 in southern Finland. The stock expansion continued for 93 years noting interim results, which were available for 1959, 1982, 1994 and 1999. Forested area in the region hardly changed. Carbon sequestration was mainly a result of a long-term recovery from forest degradation, a legacy of land use in the 18th and 19th centuries. Tree demography responded to management change especially of mature stands: Average tree size and stocking density of stands increased. On average the expanding biomass stock sequestered 18 tons C annually per km2 (18 g C per m2). In comparison, the emissions of fossil carbon in the region were estimated at 12 tons C per km2 (12 g C per m2) on average. However, fossil CO2 emissions exceeded biomass sequestration in recent decades. The powerful and persistent expansion of the carbon stock was an unintended co-benefit of forestry, which was motivated by the intention to improve timber yield. On the more negative side the change in management introduced clear-cuts, and a loss of diverse elements of the pre-industrial biota. 相似文献
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Jeff R. Powell Rachel G. Campbell Kari E. Dunfield Robert H. Gulden Miranda M. Hart David J. Levy-Booth John N. Klironomos K. Peter Pauls Clarence J. Swanton Jack T. Trevors Pedro M. Antunes 《Applied soil ecology》2009,41(1):128-136
Most soybeans grown in North America are genetically modified (GM) to tolerate applications of the broad-spectrum herbicide glyphosate; as a result, glyphosate is now extensively used in soybean cropping systems. Soybean roots form both arbuscular mycorrhizal (AM) and rhizobial symbioses. In addition to individually improving host plant fitness, these symbioses also interact to influence the functioning of each symbiosis, thereby establishing a tripartite symbiosis. The objectives of this study were to (1) estimate the effects of glyphosate on the establishment and functioning of AM and rhizobial symbioses with GM soybean, and (2) to estimate the interdependence of the symbioses in determining the response of each symbiosis to glyphosate. These objectives were addressed in two experiments; the first investigated the importance of the timing of glyphosate application in determining the responses of the symbionts and the second varied the rate of glyphosate application. Glyphosate applied at recommended field rates had no effect on Glomus intraradices or Bradyrhizobium japonicum colonization of soybean roots, or on soybean foliar tissue [P]. N2-fixation was greater for glyphosate-treated soybean plants than for untreated-plants in both experiments, but only when glyphosate was applied at the first trifoliate soybean growth stage. These data deviate from previous studies estimating the effect of glyphosate on the rhizobial symbiosis, some of which observed negative effects on rhizobial colonization and/or N2-fixation. We did observe evidence of the response of one symbiont (stimulation of N2-fixation following glyphosate) being dependent on co-inoculation with the other; however, this interactive response appeared to be contextually dependent as it was not consistent between experiments. Future research needs to consider the role of environmental factors and other biota when evaluating rhizobial responses to herbicide applications. 相似文献
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Gretchen D. Statz DVM Kari E. Moore DVM DACVECC Robert J. Murtaugh DVM MS DACVIM DACVECC 《Journal of Veterinary Emergency and Critical Care》2007,17(1):77-85
Objective: To describe the surgical repair and pre‐ and postoperative management of a peritoneopericardial diaphragmatic hernia (PPDH) in a pregnant dog. Case summary: A pregnant dog was presented for vomiting, lethargy, and pale mucous membranes. Pulsus paradoxus was noted on physical examination. The dog was diagnosed with a PPDH via thoracic radiographs, abdominal ultrasound, and an echocardiogram. The hernia was surgically repaired and the dog received supportive medical care until the puppies were old enough to be delivered via cesarean section. The mother and all puppies survived. New or unique information provided: This is the first report that describes the surgical repair and postoperative management of a PPDH in a pregnant dog. 相似文献
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温室条件下,用NaCl和Na2SO4处理石头扁桃、桃扁桃和毛桃,处理浓度为0,75,150,300和350 mmol/L,处理10,20 d分别取叶、根和茎,测定各器官中离子吸收与分布变化规律。研究结果表明,盐胁迫下,3种砧木根、茎、叶中Na ,Cl-,SO42-含量及Na /K 比均随盐浓度的增加和处理时间的延长而增加,K 含量变化规律不稳定,但桃扁桃根、茎和叶片中K 略高于其他两个品种;石头扁桃根、茎、叶片中Na /K 比值高于其它两个品种,桃扁桃中Na /K 比值最低。桃扁桃根部Na ,Cl-和SO42-含量高于石头扁桃和毛桃,而叶片和茎中Na ,Cl-和SO42-含量却低于石头扁桃和毛桃。桃扁桃根部能够积累较多的Na ,阻止和减少了Na 向地上部的运输,从而减轻了Na2SO4对它的伤害,进而表明了桃扁桃耐盐能力较强。 相似文献
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Two digestibility trials and two growth trials were carried out to evaluate the influence of top‐sprayed phytase on apparent digestibility coefficients (ADCs) of protein and mineral and utilization in rainbow trout fed with soybean meal‐based diets. In Trial 1, a semi‐purified diet containing 50% soybean meal was supplemented with graded levels of phytase (0, 500, 1000, 2000 and 4000 U kg?1 diet), and fed to triplicate groups of fish. In Trial 2, commercial‐type extruded feeds containing 36% soybean meal with either 0 or 2000 U phytase kg?1 were fed to five replicate groups of fish. Phytase clearly decreased phytic acid content of feces from 35 to 5 mg and from 34 to 14 mg phytic acid per g faecal dry matter in Trials 1 and 2 respectively. Apparent digestibility coefficient of P improved from 23% to 83% in Trial 1 and from 35% to 54% in Trial 2 by phytase. Apparent protein increased by 1.2% and 3.2%‐units by phytase in Trials 1 and 2. Zinc digestibility was significantly increased in Trial 1, but not in Trial 2. Trials 3 and 4 were conducted to evaluate the influence of phytase on dietary P (Trial 3) and lysine (Trial 4) utilization. Three diets were prepared for each trial: P (Trial 3)‐ or lysine (Trial 4)‐deficient basal diets, basal diets with phytase supplementation (2000 U kg?1) and P (Trial 3)‐ or lysine (Trial 4)‐fortified diets. Rainbow trout (initial weight 20 g) were fed for 10 weeks using four and six replicates for Trials 3 and 4 respectively. Phytase increased P utilization in Trial 3 as demonstrated by an increase in vertebra ash from 24.1% to 45.4%, and by an increase in weight gain from 243% to 459% of the initial weight. Phytase did not increase lysine utilization, since neither protein retention nor weight gain were enhanced by phytase. Supplemental lysine increased protein retention and weight gain to 43.1% and 514%, respectively, and also decreased whole‐body lipid contents significantly from 120 to 123 g kg?1 in fish fed the basal diet and phytase‐supplemented diet to 106 g kg?1 in fish fed with lysine‐fortified diet. 相似文献
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Päivi Mäkiranta Kari Minkkinen Jyrki Hytönen Jukka Laine 《Soil biology & biochemistry》2008,40(7):1592-1600
Partitioning soil respiration (SR) into its components, heterotrophic and rhizospheric respiration, is an important step for understanding and modelling carbon (C) cycling in organic soils. However, no partitioning studies on afforested organic soil croplands exist. We separated soil respiration originating from the decomposition of peat (SRP), and aboveground litter (SRL) and root respiration (SRR) in six afforested organic soil croplands in Finland with varying tree species and stand ages using the trenching method. Across the sites temporal variation in SR was primarily related to changes in soil surface temperature (?5 cm), which explained 71–96% of variation in SR rates. Decomposition of peat and litter was not related to changes in water table level, whereas a minor increase in root respiration was observed with the increase in water table depth. Temperature sensitivity of SR varied between the different respiration components: SRP was less sensitive to changes in soil surface temperature than SRL or SRR. Factors explaining spatial variation in SR differed between different respiration components. Annual SRP correlated positively with peat ash content while that of SRL was found to correlate positively with the amount of litter on the forest floor, separately for each tree species. Root respiration correlated positively with the biomass of ground vegetation. From the total soil respiration peat decomposition comprised a major share of 42%; the proportion of autotrophic respiration being 41% and aboveground litter 17%. Afforestation lowered peat decomposition rates. Nevertheless the effect of agricultural history can be seen in peat properties for decades and due to high peat decomposition rates these soils still loose carbon to the atmosphere. 相似文献
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Maria Holmberg Anu Akujärvi Saku Anttila Lauri Arvola Irina Bergström Kristin Böttcher Xiaoming Feng Martin Forsius Inese Huttunen Markus Huttunen Yki Laine Heikki Lehtonen Jari Liski Laura Mononen Katri Rankinen Anna Repo Vanamo Piirainen Pekka Vanhala Petteri Vihervaara 《Landscape Ecology》2015,30(3):561-577
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Thorleifsson G Magnusson KP Sulem P Walters GB Gudbjartsson DF Stefansson H Jonsson T Jonasdottir A Jonasdottir A Stefansdottir G Masson G Hardarson GA Petursson H Arnarsson A Motallebipour M Wallerman O Wadelius C Gulcher JR Thorsteinsdottir U Kong A Jonasson F Stefansson K 《Science (New York, N.Y.)》2007,317(5843):1397-1400
Glaucoma is a leading cause of irreversible blindness. A genome-wide search yielded multiple single-nucleotide polymorphisms (SNPs) in the 15q24.1 region associated with glaucoma. Further investigation revealed that the association is confined to exfoliation glaucoma (XFG). Two nonsynonymous SNPs in exon 1 of the gene LOXL1 explain the association, and the data suggest that they confer risk of XFG mainly through exfoliation syndrome (XFS). About 25% of the general population is homozygous for the highest-risk haplotype, and their risk of suffering from XFG is more than 100 times that of individuals carrying only low-risk haplotypes. The population-attributable risk is more than 99%. The product of LOXL1 catalyzes the formation of elastin fibers found to be a major component of the lesions in XFG. 相似文献