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1.
冬小麦不同株型品种和灌溉类型是影响产量遥感估测的重要因素, 对二者的实时监测可以提高产量的估测精度。结合遥感数据(MODIS 数据)与非遥感数据(GPS 数据和外业调查资料), 研究了不同株型品种冬小麦在水、旱地条件下归一化差值植被指数(NDVI)的动态变化特征, 分析了不同生育时期NDVI 与产量之间的关系。结果表明: 冬小麦不同株型品种间NDVI 随生育时期的变化具有明显一致性, 呈“小-大-小”变化趋势; 拔节期至孕穗期不同株型品种冬小麦NDVI 差异显著, 披散型品种高于紧凑型品种, 该时期为准确识别冬小麦株型的最佳时期。水、旱地同一种株型的冬小麦品种在整个生育时期NDVI 均值差异较显著, 均表现为水地冬小麦高于旱地冬小麦, 尤以抽穗初期最为明显。水旱地冬小麦不同生育时期NDVI 与产量相关性均以抽穗初期为最高, 但用抽穗初期和灌浆期NDVI 与产量的复合回归方程进行产量预测比用抽穗初期NDVI 与产量的回归方程效果好, 旱地冬小麦尤为明显。 相似文献
2.
A purified allophane clay fraction increased the respiration of Escherichia coli (ATCC 11303B) by buffering the suspension against decreases in pH. Allophane had no significant effect on respiration in the presence of 0.02 M phosphate buffer. When E. coli was exposed to pH values below 5.0 in the presence of allophane, allophane supernatant (which contains soluble Al), or soluble Al. toxicity was evident even after raising the pH to 7.0. 相似文献
3.
Sorptive interactions between Escherichia coli (ATCC 11303B) and a purified allophane clay fraction were studied quantitatively using electronic particle counting and electrophoresis. Adsorption was influenced by pH and ions present at the allophane surface. These effects could be rationalized by considering changes in the net surface charge of the components. Electronic particle counting studies at pH 5.5 and above gave adsorption isotherms that obeyed single-term Langmuir kinetics. At pH 4.5, a more complex two-step isotherm was obtained, which was attributed to aggregation of unadsorbed cells by Al solubilized from the allophane surface. 相似文献
4.
印度芥菜(Brassica juncea L.)重金属耐性机理研究进展 总被引：4，自引：0，他引：4
印度芥菜可富集/忍耐Cd、Zn 等多种重金属, 是研究植物修复技术的一种模式植物。高浓度的重金属离子会改变植物的基因表达、细胞形态、细胞结构, 最终使植物生长受抑, 甚至死亡。印度芥菜高效的抗氧化系统、损伤修复系统以及对重金属的螯合、区域化可部分解除重金属的毒性, 缓解重金属离子的毒害作用。利用基因工程技术在印度芥菜中导入重金属耐性及运输相关基因可大幅度提高其重金属富集能力, 在重金属污染修复方面具有广阔的应用前景。 相似文献
5.
Janet Mitchell 《Biological conservation》1976,9(1):25-28
Growth layers in the dentine of about 75 dugong, Dugong dugon (Müller), unworn permanent incisor teeth have been examined with a view to absolute age determination. Thirteen of these teeth come from complete skulls which had previously been allocated relative ages within three arbitrary life stage groups (Mitchell, 1973). The layer numbers found range from zero to , with a continuous scatter between the two extremes. It appears that the layers are either annual or biannual, and it is suggested that the dugong can attain an age of just under 60 or just under 30 years and reaches sexual maturity at about 10 or 5 years. A full account of this work is in preparation. 相似文献
6.
A survey was made in 1972, of the status of Rhododendron pronticum L. at Winterton, Norfolk, and aerial photographs were used to assess its spread in recent years. The ecological implications of the continuing presence of this invsive alien shrub on the dunes are discussed. Comparisons with the highly successfull dune shrub Hippophaë rhamnoides L. help put into perspective the present and likely future role of Rhododendron at Winterton. The implications of controls are discussed together with methods by which this may be achieved. 相似文献
7.
丛枝菌根真菌(Glomus caledonium)对铜污染土壤生物修复机理初探 总被引：12，自引：2，他引：12
利用盆栽试验,研究了丛枝菌根真菌(Glomus.caledonium)在不同程度铜污染土壤上对玉米苗期生长的影响。结果表明,即使在土壤施铜量达150mg/kg时,菌根真菌对玉米仍有近55%的侵染率;接种菌根真菌,能显著促进玉米根系的生长。菌根玉米的根系生物量和根系长度,平均较未接种处理分别提高108.4%和58.8%;接种处理的植株地上部生物量达到每盆(3株)10.58g,显著高于不施铜的非菌根玉米。这些结果表明,丛枝菌根真菌对铜污染具有较好的抗性;并且由于菌根的形成,使宿主植物明显地改善了对磷的吸收和运输,并能通过抑制土壤酸化、降低土壤可溶态铜的浓度等机制,增强宿主植物对铜污染的抗(耐)性。在150mg/kg施铜水平时,与非菌根玉米相比,菌根玉米地上部和根系铜浓度分别降低24.3%和24.1%,吸铜量分别提高了28.2%和60.0%,表明菌根植物对铜污染土壤具有一定的生物修复作用。 相似文献
8.
Love DalénAnders Götherström Magnus TannerfeldtAnders Angerbjörn 《Biological conservation》2002,105(2):171-178
The arctic fox population in Fennoscandia is on the verge of going extinct after not being able to recover from a severe bottleneck at the end of the 19th century. The Siberian arctic fox population, on the other hand, is large and unthreatened. In order to resolve questions regarding gene flow between, and genetic variation within the populations, a 294 bp long part of the mitochondrial hypervariable region 1 was sequenced. This was done for 17 Swedish, 15 Siberian and two farmed foxes. Twelve variable nucleotide sites were observed, which resulted in 10 different haplotypes. Three haplotypes were found in Sweden and seven haplotypes were found in Siberia. An analysis of molecular variance showed a weak, but significant, differentiation between the populations. No difference in haplotype diversity was found between the populations. A phylogenetic analysis revealed that the three Swedish haplotypes were not monophyletic compared to the Siberian haplotypes. These results indicate a certain amount of gene flow between the two populations, both before and after the bottleneck. Restocking the Fennoscandian population with arctic foxes from Siberia might therefore be a viable option. 相似文献
9.
The population and distribution of sclerotia of Rhizoctonia solani Kühn in two sugar beet field soils was determined at harvest by a sieving-flotation method. In rhizosphere soil (RS) and non-rhizosphere soil (NRS) from the most heavily infected roots of sugar beets, 1.43–2.5 and 0.83–1.0 sclerotia g?1 dry soil were detected, respectively. In the soil around healthy sugar beet, these values were 0.04–0.12 and 0.03–0.04 sclerotia g?1 dry soil. More sclerotia were always obtained from RS than from NRS. More than 80% of the sclerotia were in the upper 10 cm of soil and within 10 cm of diseased roots. Therefore, there is a non-uniform distribution of sclerotia of R. solani in soil.The sclerotial population in soil increased significantly with disease severity and a good correlation was obtained between the number of sclerotia and the disease severity on infected plants. Most of the sclerotia collected from the field soil ranged in size from 0.5 to 2.0 mm diameter.Viability of sclerotia increased as severity of crown rot increased and as the size of the sclerotia increased. Conversely, there was a progressive decrease in sclerotial germination with increasing depth in soil and increasing distance from the infected root. 相似文献
10.
11.
The relative importance of time since disturbance and habitat variables in creating diversity in old-growth forests will influence conservation strategies. However, the independent roles of these factors are not well understood, as they are rarely examined independently. This study examines the respective roles of habitat variables and time (stand age) in determining bryophyte diversity in Picea mariana (Mill. (BSP)) forests. Bryophytes are frequently used as indicators of old-growth forest, but their true dependence on forest continuity is unknown. Bryophytes were classified into taxonomic-habitat guilds: true mosses (forest), forest liverworts, bog liverworts and sphagna (bog). Diversity increased with age and peaked at approximately 275 years since fire, driven by liverworts. Multiplicative habitat modeling indicated that time and habitat played different roles for the different taxonomic-habitat guilds. True mosses and forest liverworts were primarily influenced by habitat variables, while sphagna and bog liverworts were influenced by time and habitat variables. The models for sphagna were particularly strong, indicating that many important factors were included, while forest liverwort models were particularly weak. This unexplained variability may represent site specific random factors, such as secondary disturbances that create habitat in a fully occupied space. Overall, high richness was created by small species dependent on habitat variables and chance factors for establishment. Therefore, time since disturbance was not the primary factor limiting richness in these forests. These results suggest that in boreal North America, where forest fragmentation is limited and recent, conservation strategies that emphasize habitat variables rather than forest continuity may be effective for some bryophytes. 相似文献
12.
B.J. Macauley 《Soil biology & biochemistry》1979,11(2):175-179
Fungal succession on untreated and fungicide- and insecticide-treated leaves of Eucalyptus pauciflora was compared. Natural succession on untreated leaves fits the general scheme for succession on deciduous tree leaves. Initial colonizers are species of Coelomycetes and Moniliales. When the numbers of Coelomycetes decrease in the late stages of decomposition, the frequency of Penicillium species and species of Zygomycetes increases. The succession is affected only marginally by DDT and dieldrin treatment while benomyl severely restricts the occurrence of most fungal species. The effect of benomyl persists even after exposure for 48 weeks in the field. 相似文献
13.
An attempt to reintroduce the white-tailed sea eagle to the west of Scotland was initiated by the Nature Conservancy Council in 1975, on the Isle of Rhum. Four eaglets were obtained from Norway that year; one of them died in captivity and the other three (all females) were released. Ten more were acquired in 1976 and a further four in 1977. Of these a total of 13 (8♀ and 5♂) had been released into the wild by May 1977. Two have since been recovered dead, but the others apparently adapted readily to a free-living existence. Eight more are to be released during 1978. The first nesting attempts can be expected once the young birds reach sexual maturity at 5 years of age (possibly in 1980 or 1981). 相似文献
14.
Clare M. O’Brien Mathew S. Crowther Christopher R. Dickman 《Biological conservation》2008,141(8):1962-1971
Many species that exist patchily across the landscape are declining due to incremental losses of their constituent sub-populations and increasing isolation of those that remain. For threatened species with such patchy metapopulation structure, it is particularly important to identify key habitat patches and understand what factors govern their occupancy so that their management can be targeted and effective. In this paper, we describe the spatial and temporal distribution of an endangered population of broad-toothed rats (Mastacomys fuscus) at Barrington Tops, New South Wales, and model its dynamics using metapopulation theory. The study population occurs patchily in swamps on the Barrington Plateau. Using faecal pellet searches, live-trapping and data from previous surveys, we identified 12 swamps where M. fuscus persists and 13 where there has been a history of colonisation and extinction. The species now appears to be entirely absent from seven of these latter swamps. Using logistic regression and model selection procedures, we found the strongest predictor of the presence of M. fuscus to be proximity to the nearest occupied swamp. Persistence declined strongly with swamp isolation, probably due to low success of individuals dispersing through the intervening habitat. These patterns support the interpretation that swamp patches at Barrington Tops contain a functioning but fragile metapopulation of M. fuscus. We predict continued loss of remaining sub-populations in peripheral swamps if current dynamics continue, and recommend research to identify the factors that are limiting dispersal and re-colonisation so that the species’ decline can be slowed and reversed. 相似文献
15.
Rhizobia isolated from fourteen different genera of legumes were tested for their N-fixing effectiveness with Psophocarpus tetragonolobus in standard Leonard jar trials. Isolates from all plants except Pithecellobium jiringa were able to form nodules with P. tetragonolobus although a wide range of effectiveness amongst the different rhizobia was demonstrated. Thus P. tetragonolobus may be considered promiscuous with respect to its rhizobial requirements. Based on this experiment, a group of rhizobia comprising three elite strains (RRIM 56 from P. tetragonolobus, UMKL 36 from Lablab purpureus and CB 756 from Macrotyloma africanum, a moderately effective strain (NGR 258 from P. tetragonolobus), and two strains of low effectivity (RRIM 968 from Centrosema pubescens and UMKL 12 from Phaselus angularis) were selected for further study. When these were used to inoculate P. tetragonolubus growing in soil taken from virgin jungle (less than 1.54 rhizobia g?1 soil); RRIM 56 and UMKL 36 again performed well, but NGR 258 outperformed CB 756. 相似文献
16.
John Kowarsky 《Biological conservation》1978,13(1):51-62
Surveys of nesting activity of green turtles (Chelonia mydas) were conducted in the Torres Strait region during the 1975–1976 nesting season. Very few of the numerous beaches examined showed any evidence of heavy use by nesting turtles. During that season there were widespread reports of lower than usual nesting activity by green turtles in north-eastern Australia. Biological information from nesting green turtles in the Torres Strait region was very similar to comparable data available for green turtles nesting at Heron Island, located further south. 相似文献
17.
Biochar amendments to soils have been suggested as a strategy to sequester carbon and therefore mitigate global climate change. The enrichment of soils with charred materials also increases their fertility. This fertilising effect of biochar may be caused by various mechanisms; an acceleration of nutrient cycling has been suggested as one such mechanism. The rate-limiting step in nutrient cycling is thought to be the extracellular enzymatic attack on biological macromolecules. In this study, therefore, the effects of chestnut wood char (specific surface area 2.0 m2 g−1) and of activated carbon (specific surface area approximately 900 m2 g−1) on an extracellular enzymatic reaction involved in the degradation of cellulose (i.e., hydrolysis of cellobiose by β-glucosidase from Aspergillus niger) were investigated. Cellobiose was not adsorbed by chestnut wood char, whereas activated carbon absorbed more than 97% of it. Both charred materials adsorbed more than 99% of β-glucosidase. For chestnut wood char, adsorption of the enzyme caused a decrease of approximately 30% in the reaction rate, whereas for activated carbon, the nearly complete absorption of both substrate and enzyme entirely inhibited the reaction. These results show that β-glucosidase from A. niger retains most of its activity when adsorbed to chestnut wood char and that the reaction it catalyses in nature is only slightly affected by this charred material. On the other hand, a material characterised by a high specific surface area and high porosity, such as activated carbon, can make even a highly soluble substrate unavailable for soil enzymes and therefore completely inhibit the reaction. Thus, charred materials may affect nutrient cycling mainly by regulating the availability of substrates: the degradation of highly soluble substrates may be accelerated by materials with low specific surface area, which maintain an active and protected enzyme pool, whereas materials with high specific surface and high porosity may slow down the degradation by making substrates unavailable. 相似文献
18.
The ability of four strains of Rhizobium trifolii to colonize host-root and soil was compared at 5-day intervals up to 70 days from sowing into a field soil. Strain differences in colonizing ability were demonstrated, with one strain (TA1) consistently inferior to the other three which comprised another introduced strain (UNZ29) and two locally isolated strains. 相似文献
19.
Antisera were prepared against six inoculant strains of rhizobia for Psophocarpus tetragonolobus, and used to react with 62 different strains in both agglutination and immunodiffusion systems. A wide array of reactions occurred, indicating the extent of heterogeneity amongst strains capable of nodulating the same host. In agglutination reactions, the heat-stable somatic antigens could be arranged in 25 serogroups. In gel diffusion, antigens which produced strong precipitin bands usually showed agglutination relationships, but the corollary was not true. The immunodiffusion technique easily distinguished homologous and cross-reacting reactions and could be reliably used in field experiments with P. tetragonolobus. 相似文献
20.
Enrique Alarcón-Gutiérrez Fabio Ziarelli Stéven Criquet 《Soil biology & biochemistry》2010,42(2):283-290
In a Mediterranean climate, water stress is one of the principal constraints on proper forest ecosystem functioning. Drought influences rates of organic matter degradation by affecting microbial growth and enzyme activities. The objectives of this study were: (i) to evaluate the effect of repeated drying-rewetting cycles on cellulase, alkaline phosphatase and fluorescein diacetate (FDA) hydrolase activities of three distinct Quercus ilex L. litter layers, and (ii) to investigate the effect of these cycles on γ-irradiated litters in order to distinguish the abiotic influence on the fluctuations observed. Results, for all three layers, showed high correlations between litter water content and enzyme activities. Under mesocosm conditions, and using non-sterilized litter samples, cellulase, alkaline phosphatase, and FDA activities significantly decreased or increased during drying or rewetting cycles respectively. Significant differences were also found when evaluating the effect of litter depth on enzyme activities, the intermediate depth (OLv layer) generally being the most active. For γ-sterilized samples, FDA activity still fluctuated with drying-rewetting cycles. Assays showed that pre-humidification of γ-irradiated litter increased FDA activity two-fold in the first 30 min. All these results have shown that, following drying-rewetting cycles, some of the fluctuations occur independently of microbial growth, suggesting abiotic interactions, such as desorption, in combination with both solvatation status and conformational changes of enzymes. 相似文献