Soil microbial biomass and population in response to seasonal variation and age in Gmelina arborea plantations in south-western Nigeria     

Jonathan C. Onyekwelu 《林业研究》2012,23(2):253-260

We investigated the Effects of plantation development, seasons, and soil depth on soil microbial indices in Gmelina arborea plantations in south-western Nigeria. Soil samples were obtained from the soil depths of 0-15 and 15-30 cm from plantations of six different ages during the rainy season, dry seasons, and their transitions. We used plate count and fumigation-extraction methods to determine microbe population and microbial biomass carbon (MB-C) and nitrogen (MB-N), respectively. Plantation age did not affect microbial indices, implying a non-significant effect of plantation development on microbial communities. It could also imply that soil microbial indices had already stabilized in the sampled plantations. Seasonal variation and soil depth had significant effects on microbial indices. At 0-15 cm soil depth, mean MB-C increased from 50.74 μg g-1 during the peak of the dry season (i.e. March) to 99.58 μg g-1 during the peak of the rainy season (i.e. September), while it increased from 36.22 μg g-1 to 75.31 μg g-1 at 15-30 cm soil depth between the same seasonal periods. Bacteria populations and MB-N showed similar increasing trends. Correlations between MB-C, MB-N, microbe populations, and rainfall were positive and linear. Significantly higher microbial activities took place in the plantations during the rainy season, increased with soil wetness, and decreased at greater soil depth.  相似文献   

A novel technique for non-damaging measurement of sound speed in seedlings     

Grant Emms  Bernadette Nanayakkara  Jonathan Harrington 《European Journal of Forest Research》2012,131(5):1449-1459

A cross-correlation time-of-flight method for measuring the sound speed in a seedling in a non-destructive and non-damaging way is described. The method uses two miniature accelerometers coupled to the bark of a growing seedling stem to record the acoustic signals and a small striker to generate an acoustic pulse. The two acoustic signals are then time-windowed and cross-correlated in order to calculate the speed of the acoustic pulse. The method measures the sound speed of the seedling stem as a whole and does not selectively measure the fastest path. The method was tested on 1- and 2-year-old Pinus radiata clones. A comparison of the results of the method with a destructive acoustic resonance test showed that the sound speed results are unbiased. Repeatability tests give a standard deviation of the sound speed of less than 2%. The method shows good promise as a rapid and cost-effective tool for early screening of wood quality in clonal trials.  相似文献   

Effects of phenylbutazone on gene expression of cyclooxygenase-1 and -2 in the oral, glandular gastric, and bladder mucosae of healthy horses     

Nieto JE  Aleman M  Anderson JD  Fiack C  Snyder JR 《American journal of veterinary research》2012,73(1):98-104

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Family-centred veterinary medicine: learning from human paediatric care     

Williams D  Jewell J 《The Veterinary record》2012,170(3):79-80

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Humanitarian crises, livelihoods and veterinary interventions     

Okell C  Rushton J  Verheyen K 《The Veterinary record》2012,170(8):211

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Integrating local breeding pond, landcover, and climate factors in predicting amphibian distributions     

Daryl R. Trumbo  Amber A. Burgett  Robert L. Hopkins  Elizabeth G. Biro  Jonathan M. Chase  Jason H. Knouft 《Landscape Ecology》2012,27(8):1183-1196

Species distributions are influenced by many processes operating over varying spatial scales. The development of species distribution models (SDMs), also known as ecological niche models, has afforded the opportunity to predict the distributions of diverse taxa across broad geographic areas and identify variables that are potentially important in regulating these distributions. However, the integration of site-specific habitat data with broad scale climate and landcover data has received limited attention in an SDM framework. We investigate whether SDMs developed with breeding pond, landcover, and climate variables can accurately predict the distributions of nine pond-breeding amphibians in eastern Missouri, USA. Additionally we investigate the relative influences of each environmental variable on the distribution predictions for each study species, and whether the most influential variables are shared among multiple taxa. Boosted regression tree (BRT) SDMs were developed for each species with 38 abiotic and biotic environmental variables, including data from the breeding ponds, surrounding landcover, and climate. To test the models, field surveys were performed in 2007 and 2008 at 103 ponds for nine amphibian species. BRT models developed with breeding pond, landcover, and climate data accurately predicted the occurrences of six of nine species across the study area. Furthermore, the presence of each species was best predicted by a unique combination of environmental variables. Results also suggest that landcover and climate factors may be more influential for species near the edge of their geographic ranges, while local breeding pond factors may be more important for species nearer to the center of their ranges.  相似文献   

Influence of year and genetic factors on chilling injury susceptibility in peach (<Emphasis Type="Italic">Prunus persica</Emphasis> (L.) Batsch)     

Pedro J. Martínez-García  Cameron P. Peace  Dan E. Parfitt  Ebenezer A. Ogundiwin  Jonathan Fresnedo-Ramírez  Abhaya M. Dandekar  Thomas M. Gradziel  Carlos H. Crisosto 《Euphytica》2012,185(2):267-280

Chilling injury (CI) is a major physiological problem limiting consumption and export of peach and nectarine (Prunus persica (L.) Batsch). To clarify the genetic basis for chilling injury, inheritance of the major CI symptoms mealiness, flesh browning, flesh bleeding, and flesh leatheriness were examined over three years in two related peach progenies. In addition, genetic relationships among traits and the year-to-year variation in trait performance in these progenies were tracked. Both populations also segregated for Freestone-Melting flesh (F-M) and yellow flesh. There were significant differences in CI symptoms among years. The major gene endoPG, which controls the F-M locus, provides resistance to mealiness in non-melting flesh fruit. Only fruit with melting flesh can develop mealiness if the tree possesses other genetic susceptibility factors and/or experiences inducing conditions. The F-M locus also greatly influences susceptibility to flesh bleeding, although the physiological mechanism for this disorder is unclear and may be controlled by a different gene closely linked to endoPG. Unlike mealiness, flesh bleeding occurred primarily in non-melting flesh fruit, particularly when the fruit is white-fleshed. Flesh browning incidence was greater in mealy fruit and was not associated with flesh bleeding. Breeding for CI resistance is thus a viable long-term strategy to reduce losses in the fresh and processed peach and nectarine industries. This study is an important first step to understanding genetic control of CI symptoms in peach.  相似文献   

Soil Metagenome of Tropical White Sand Heath Forests in Borneo:What Functional Traits Are Associated with an Extreme Environment Within the Tropical Rainforest?     

Dorsaf KERFAHI  Binu M. TRIPATHI  Johan W. Ferry SLIK  Rahayu S. SUKRI  Salwana JAAFAR  Ke DONG  Matthew Chidozie OGWU  Hyo-Ki KIM  Jonathan M. ADAMS 《土壤圈》2019,29(1):12-23

White sand heath forests (WS) or kerangas, an unusual variant of tropical forests in Borneo, characterized by open scrubby vegetation, low productivity, and distinctive plant species composition and soil microbial community, are regarded as a stressful low-pH and/or nutrient environment. We investigated whether the functional soil metagenome also shows a predicted set of indicators of stressful conditions in WS. Based on stress-tolerant strategies exhibited by larger organisms, we hypothesized that genes for stress tolerance, dormancy, sporulation, and nutrient processing are more abundant in the soil microbiota of WS. We also hypothesized that there is less evidence of biotic interaction in white sand soils, with lower connectivity and fewer genes related to organismic interactions. In Brunei, we sampled soils from a WS and a normal primary dipterocarp forest, together with an inland heath, an intermediate forest type. Soil DNA was extracted, and shotgun sequencing was performed using Illumina HiSeq platform, with classification by the Metagenomics Rapid Annotation using Subsystem Technology (MG-RAST). The results, on one hand, supported our hypothesis (on greater abundance of dormancy, virulence, and sporulation-related genes). However, some aspects of our results showed no significant difference (specifically in stress tolerance, antibiotic resistance, viruses, and clustered regularly interspaced short palindrome repeats (CRISPRs)). It appears that in certain respects, the extreme white sand environment produces the predicted strategy of less biotic interaction, but exhibits high soil microbiota connectivity and functional diversity.  相似文献   

The Alliance for Freshwater Life: A global call to unite efforts for freshwater biodiversity science and conservation          下载免费PDF全文

William Darwall  Vanessa Bremerich  Aaike De Wever  Anthony I. Dell  Jörg Freyhof  Mark O. Gessner  Hans‐Peter Grossart  Ian Harrison  Ken Irvine  Sonja C. Jähnig  Jonathan M. Jeschke  Jessica J. Lee  Cai Lu  Aleksandra M. Lewandowska  Michael T. Monaghan  Jens C. Nejstgaard  Harmony Patricio  Astrid Schmidt‐Kloiber  Simon N. Stuart  Michele Thieme  Klement Tockner  Eren Turak  Olaf Weyl 《水产资源保护:海洋与淡水生态系统》2018,28(4):1015-1022

Self-assembled hexa-peri-hexabenzocoronene graphitic nanotube     

Hill JP  Jin W  Kosaka A  Fukushima T  Ichihara H  Shimomura T  Ito K  Hashizume T  Ishii N  Aida T 《Science (New York, N.Y.)》2004,304(5676):1481-1483

An amphiphilic hexa-peri-hexabenzocoronene self-assembles to form a pi-electronic, discrete nanotubular object. The object is characterized by an aspect ratio greater than 1000 and has a uniform, 14-nanometer-wide, open-ended hollow space, which is an order of magnitude larger than those of carbon nanotubes. The wall is 3 nanometers thick and consists of helical arrays of the pi-stacked graphene molecule, whose exterior and interior surfaces are covered by hydrophilic triethylene glycol chains. The graphitic nanotube is redox active, and a single piece of the nanotube across 180-nanometer-gap electrodes shows, upon oxidation, an electrical resistance of 2.5 megohms at 285 kelvin [corrected]. This family of molecularly engineered graphite with a one-dimensional tubular shape and a chemically accessible surface constitutes an important step toward molecular electronics.  相似文献