Influence of phylogeny on fungal community assembly and ecosystem functioning     

Maherali H  Klironomos JN 《Science (New York, N.Y.)》2007,316(5832):1746-1748

Ecology seeks to explain species coexistence and its functional consequences, but experimental tests of mechanisms that simultaneously account for both processes are difficult. We used an experimental mycorrhizal plant system to test whether functional similarity among closely related species (phylogenetic conservatism) can drive community assembly and ecosystem functioning. Communities were constructed with the same number of fungal species, but after 1 year of growth, realized species richness was highest where the starting species were more distantly related to each other. Communities with high realized species richness also stimulated plant productivity more than those with low realized species richness. Our findings suggest that phylogenetic trait conservatism can promote coexistence because of reduced competition between distinct evolutionary lineages and enhance ecosystem function because of functional complementarity among those same lineages.  相似文献   

Development of on-line measurement system of bulk density based on on-line measured draught, depth and soil moisture content     

Abdul Mounem Mouazen  Herman Ramon 《Soil & Tillage Research》2006,86(2):218-229

On-line measurement of soil compaction is needed for site specific tillage management. The soil bulk density (ρ) indicating soil compaction was measured on-line by means of a developed compaction sensor system that comprised several sensors for on-line measurement of the draught (D) of a soil cutting tool (subsoiler), the soil cutting depth (d) and the soil moisture content (w). The subsoiler D was measured with a single shear beam load cell, whereas d was measured with a wheel gauge that consisted of a swinging arm metal wheel and a linear variable differential transducer (LVDT). The soil w was measured with a near infrared fibre-type spectrophotometer sensor. These on-line three measured parameters were used to calculate ρ, by utilising a hybrid numerical–statistical mathematical model developed in a previous study. Punctual kriging was performed using the variogram estimation and spatial prediction with error (VESPER) 1.6 software to develop the field maps of ρ, soil w, subsoiler d and D, based on 10 m × 10 m grid. To verify the on-line measured ρ map, this map was compared with the map measured by the conventional core sampling method.

The spherical semivariogram models, providing the best fit for all properties was used for kriging of different maps. Maps developed showed that no clear correlation could be detected between different parameters measured and subsoiler D. However, the D value was smaller at shallow penetration d, whereas large D coincided with large ρ values at few positions in the field. Maps of ρ measured with the core sampling and on-line methods were similar, with correlation coefficient (r) and the standard error values of 0.75 and 0.054 Mg m⁻³, respectively. On-line measured ρ exhibited larger errors at very dry zones. The normal distribution of the ρ error between the two different measurement methods showed that about 72% of the errors were less than 0.05 Mg m⁻³ in absolute values. However, the overall mean error of on-line measured ρ was of a small value of 2.3%, which ensures the method accuracy for on-line measurement of ρ. Measurement under very dry conditions should be minimised, because it can lead to a relatively large error, and hence, compacted zones at dry zones cannot be detected correctly.  相似文献   

澳大利亚一个林地环境下的切沟发展过程和侵蚀趋势研究   总被引：2，自引：0，他引：2  

MajidSoufi 《中国水土保持》2002,(7):26-27

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Earthworm casts form stable aggregates in physically degraded soils   总被引：1，自引：0，他引：1  

Abdul?R.?A.?Marashi  John?ScullionEmail author 《Biology and Fertility of Soils》2003,37(6):375-380

Topsoils affected by surface mining suffer severe physical degradation and lose most of their earthworm populations. After mining, replaced soils are planted to grassland and managed to improve soil structure. Earthworm inoculation into selected restored areas produced populations similar to those of undisturbed soils within 3 years. Soil properties in inoculated areas were compared with those of controls to evaluate the contribution of casts to bulk soil aggregation, and soil organic matter and root content responses to earthworm activity. Crumb porosity and coarse particle content were measured in water-stable macro-aggregates and earthworm casts to establish whether aggregates were formed by earthworms. Over a 5- to 6-year period, inoculation increased stable aggregation (>2 μm, >60 μm and >3 mm), even at 0- to 5-cm depth where it reduced soil organic matter content. Productivity and root content were also increased by inoculation; roots and organic matter were re-distributed to greater depth. Crumb porosity decreased with casts > aggregates (inoculated plots) > aggregates (control plots). Coarse particle content increased with casts < aggregates (inoculated plots) < aggregates (control plots). Coarse particle and porosity data were consistent with much of the newly aggregated soil being processed and formed by earthworms as casts. Whilst levels of soil organic matter were often closely associated with percentage stable aggregation, root content showed weaker associations. Aggregation percentage was most closely associated with abundance of Aporrectodea longa, although at particular depths significant correlations were also obtained for Aporrectodea caliginosa and Lumbricus terrestris. Results suggest that earthworms, rather than plant roots, initiate aggregation in severely degraded grassland soils.  相似文献   

Development and Characterization of Novel Polymorphic Microsatellite Markers for Tapinoma indicum (Hymenoptera: Formicidae)     

Li Yang Lim  Abdul Hafiz Ab Majid 《Journal of insect science (Online)》2021,21(4)

Tapinoma indicum (Forel) (Hymenoptera: Formicidae) is a nuisance pest in Asia countries. However, studies on T. indicum are limited, especially in the field of molecular biology, to investigate the species characteristic at the molecular level. This paper aims to provide valuable genetic markers as tools with which to study the T. indicum population. In this study, a total of 143,998 microsatellite markers were developed based on the 2.61 × 10⁶ microsatellites isolated from T. indicum genomic DNA sequences. Fifty selected microsatellite markers were amplified with varying numbers of alleles ranging from 0 to 19. Seven out of fifty microsatellite markers were characterized for polymorphism with the Hardy–Weinberg equilibrium (HWE) and linkage disequilibrium (LD) analysis. All seven microsatellite markers demonstrated a high polymorphic information content (PIC) value ranging from 0.87 to 0.93, with a mean value of 0.90. There is no evidence of scoring errors caused by stutter peaks, no large allele dropout, and no linkage disequilibrium among the seven loci; although loci Ti-Tr04, Ti-Tr09, Ti-Te04, Ti-Te13, and Ti-Pe5 showed signs of null alleles and deviation from the HWE due to excessive homozygosity. In conclusion, a significant amount of microsatellite markers was developed from the data set of next-generation sequencing, and seven of microsatellite markers were validated as informative genetic markers that can be utilized to study the T. indicum population.  相似文献   

A greenhouse method for screening lettuce for resistance to Sclerotinia sclerotiorum     

Abdul Madjid  Shigemi Honma  Melvyn L. Lacy 《Scientia Horticulturae》1983,18(3):201-206

Agar blocks colonized by Sclerotinia sclerotiorum, causal agent of lettuce drop, were used as inoculum in screening for resistance to this pathogen in the greenhouse.Since the degree of resistance to the pathogen among cultivars varied with the time observed after inoculation, resistance was assessed by the number of days for 50% of the plants of each cultivar to die, as well as the number of plants that died. The cultivars ‘PI (Plant Introduction) 250427’, ‘Taiwan’, ‘PI 251790’, ‘PI 255568’, ‘MSU 73-44’ and ‘Bibb’ were found to have a higher level of resistance to S. sclerotiorum than the cultivar ‘Grand Rapids’ at 12 or 15 days following inoculation.  相似文献   

Hemolytic effect of solvents. 1. Dimethylacetamide     

H J Hapke  H Majid 《DTW. Deutsche tier?rztliche Wochenschrift》1983,90(5):161-163

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Age specific prevalence and intensity of Schistosoma bovis infection in Sudanese Desert sheep in the White Nile Province     

A A Majid  M F Hussein  M G Taylor 《Research in veterinary science》1983,35(1):120-121

A survey of ovine schistosomiasis was carried out in a Schistosoma bovis enzootic area in the central Sudan. Three hundred Desert sheep, representing different age groups, were screened for infection, using Pitchford's faecal egg counting technique. No infection was detected in animals under one year old, but from the age of 18 months onward, the prevalence increased progressively from around 20 per cent to 60 per cent in six-year-old sheep, and this was accompanied by an increase in infection intensity, as determined by faecal egg counts. These findings, which suggest that these sheep did not develop an effective resistance to schistosomiasis, contrasted with those previously recorded in cattle from the same locality, studied in the same year.  相似文献   

Variation in free jumping technique within and among horses with little experience in show jumping     

Santamaría S  Bobbert ME  Back W  Barneveld A  van Weeren PR 《American journal of veterinary research》2004,65(7):938-944

OBJECTIVE: To quantify variation in the jumping technique within and among young horses with little jumping experience, establish relationships between kinetic and kinematic variables, and identify a limited set of variables characteristic for detecting differences in jumping performance among horses. ANIMALS: Fifteen 4-year-old Dutch Warmblood horses. PROCEDURE: The horses were raised under standardized conditions and trained in accordance with a fixed protocol for a short period. Subsequently, horses were analyzed kinematically during free jumping over a fence with a height of 1.05 m. RESULTS: Within-horse variation in all variables that quantified jumping technique was smaller than variation among horses. However, some horses had less variation than others. Height of the center of gravity (CG) at the apex of the jump ranged from 1.80 to 2.01 m among horses; this variation could be explained by the variation in vertical velocity of the CG at takeoff (r, 0.78). Horses that had higher vertical velocity at takeoff left the ground and landed again farther from the fence, had shorter push-off phases for the forelimbs and hind limbs, and generated greater vertical acceleration of the CG primarily during the hind limb push-off. However, all horses cleared the fence successfully, independent of jumping technique. CONCLUSIONS AND CLINICAL RELEVANCE: Each horse had its own jumping technique. Differences among techniques were characterized by variations in the vertical velocity of the CG at takeoff. It must be determined whether jumping performance later in life can be predicted from observing free jumps of young horses.  相似文献   

Comparative analysis of viral RNA and apoptotic cells in bursae following infection with infectious bursal disease virus     

Kong LL  Omar AR  Hair-Bejo M  Aini I  Seow HF 《Comparative immunology, microbiology and infectious diseases》2004,27(6):433-443

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