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31.
为研究杉木在中国的分布特征及其对气候变化的响应模式,本研究基于现有分布记录,应用最大熵(MaxEnt)模型和地理信息系统方法,结合气候、地形等环境要素,预测杉木在当前和未来气候变化下的潜在适生区。结果表明: 影响杉木分布的最主要因素是年平均降水量,在当前气候下,杉木适生区合计面积328万km2,占全国陆地总面积的34.5%,低、中和高适生区分别占18.3%、29.7%与52.0%。在未来气候情景下,杉木生长的适宜性在我国总体上呈上升趋势,适生区面积随气候变化增大,且明显向北扩张,南方湿润亚热带地区形成集中连片高适生区。模型经受试者工作特征曲线检验,训练集平均受试者工作特征曲线下面积为0.91,可信度高。 相似文献
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FREDERIQUE LE ROUX GEMA LORENZO PIERRE PEYRET CORINNE AUDEMARD ANTONIO FIGUERAS CHRISTIAN VIVARÈS MANOLO GOUY FRANCK BERTHE 《The Journal of eukaryotic microbiology》2001,48(4):449-454
Marteilia refringens is one of the most significant pathogens of bivalve molluscs. Previous sequencing of the small subunit ribosomal RNA gene of M. refringens isolates derived from the infected mussels (Mytilus edulis and Mytilus galloprovinciallis) and the oyster (Ostrea edulis) in Europe did not reveal genetic polymorphisms despite indications from epizootiological data that distinct types may exist. We investigated the existence of polymorphisms in the internal transcribed spacer region of the ribosomal RNA genes. The sequences of this region proved to be clearly dimorphic among Marteilia from five sampling sites. The distribution of the two genetic types, named "O" and "M", appeared to be linked to the host species, oysters and mussels, respectively. We therefore support the recognition of two species of Marteilia in Europe and propose that the "O" type corresponds to M. refringens and the "M" type to M. maurini. 相似文献
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A chamber for the simulation of radiation freezing of plants 总被引:1,自引:0,他引:1
Frost injury to plants can occur following episodic radiation frosts. In the UK this is particularly important to spring sown crops such as potatoes. Most laboratory based frost studies simulate freezing using either conductive or convective freezing chambers. Such frost tests do not simulate overnight freezing events adequately. A freezing chamber based on radiative cooling is described which mimics overnight radiative freezing. The chamber is rectangular in design (1 m × lm × 2 m high) with a radiative cooling plate at the top of the chamber cooled to -40°C to -45°C using HFC coolants, which acts as a cold black body. The sides of the chamber are also cooled to variable temperatures down to -5°C in order to prevent the chamber walls radiating to the plant material during testing. Using thermocouples to measure air temperature and plant temperature the chamber has been characterised to simulate the radiative cooling conditions found in the UK during autumn and spring. Exotherm detection upon plant freezing is simplified by virtue of the reduction in temperature fluctuation normally experienced at the plant surface during natural freezing. Radiation frosts and subsequent frost damage to potatoes have been recorded in the temperature range -4°C to –5°C. The equipment is recommended for studies of frost damage to plants normally caused by episodic radiation frost events. 相似文献
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The Barn Owl Tyto alba was the most common owl killed on motorways in northeastern France. The possible causes of this mortality and the age, sex and body condition of the road-killed birds in 1991–1994 have been investigated. The number of birds killed on roads was highest in the period from early autumn to late winter, i.e. during the non-breeding period, and showed a pattern similar to that of the temporal difference between sunset, which varies with day length, and peak of traffic, the occurrence of which is constant throughout the year. An autumnal mortality peak, concomitant with the post-fledging dispersal, was mainly of immature birds, especially females. A second mortality peak in late winter was composed mainly of mature birds, with an equal proportion of males and females. From autumn to winter, there was no significant change in body mass in the different age and sex categories of birds killed on roads, except for mature males which had a significantly lower body mass in winter. From early autumn to late winter, the mean body mass of immature owls killed on motorways did not differ significantly from that of captive immatures fed ad libitum. This suggests that the immature birds were in good body condition. In contrast, the body mass of road-killed mature females was significantly lower than that of captive mature females over the same time periods. In mature males in late winter, a drop in body mass in both road-killed and captive birds suggests an endogenous seasonal phenomenon. Except for mature females, Barn Owls killed on roads in 1991–1994 were in good body condition. This does not support the idea that only birds in poor body condition were killed. We conclude that the mortality of Barn Owls on motorways in autumn and winter was probably related to the concomitance between the peak of traffic and the onset of hunting activity and the large number and dispersal of immature individuals during the same period. 相似文献
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Selected strains of ectomycorrhizal fungi, such as the basidiomycete Laccaria bicolor , are currently being used as inoculants in nurseries to improve growth of forest trees after outplanting. Information is needed on the survival of these introduced strains in forests and their impact on indigenous biodiversity. Dissemination and persistence of an American strain, L. bicolor S238N, were studied 10 years after outplanting in a Douglas fir plantation located at Saint-Brisson (Morvan, France). About 430 Laccaria spp. sporophores were collected over 3 years. Inheritance of nuclear ribosomal DNA, as well as RAPD markers, was characterized in L. bicolor S238N, using a haploid progeny set of 91 monokaryons. More than 50 markers were identified (19 heterozygous and 33 homozygous or cytoplasmic markers), which unambiguously confirmed that the introduced strain was still present in the inoculated plots. Neither selfing ( P < 0.0008) nor introgression with indigenous strains was detected although in vitro interfertility between the American strain and indigenous L. bicolor was identified. No ingress of the introduced genet into adjacent uninoculated plots colonized by various local Laccaria genets was detected. It is proposed that the spatial distributions identified have developed through mycelial propagation of the introduced strain and intraspecific competition with native genets. Although longer-term data is still lacking, the stability of the inoculant strain and the limited disturbance to indigenous populations described support large-scale nursery production of this host-fungal combination. 相似文献
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J Daugherty TM Evans T Skillom LE Watson NP Money 《Fungal genetics and biology : FG & B》1998,24(3):354-363
Classical studies on spore release within the Saprolegniaceae (Oomycetes) led to the proposition that different mechanisms of sporangial emptying represent steps in an evolutionary transition series. We have reevaluated this idea in a phylogenetic framework using internal transcribed spacer sequences of four genera. These data were compared with the response to osmotic stress exhibited by each taxon. Saprolegnia emerges as the most basal genus, sister to Achlya, Thraustotheca, and Dictyuchus. Achlya and Thraustotheca are most closely related, while Dictyuchus appears to have evolved along a separate evolutionary lineage. The resulting phylogenetic framework is consistent with the idea that the mechanism of sporangial emptying exhibited by Saprolegnia represents the plesiomorphic condition from which the other mechanisms were derived independently. These alternative mechanisms of spore release may have resulted from a small number of mutations that inhibited axonemal development and altered the temporal and spatial expression of lytic enzymes that degrade the sporangial wall. Copyright 1998 Academic Press. 相似文献