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|Posted by shafiq ahmed on December 14, 2014 at 3:40 PM||comments (0)|
|Posted by shafiq ahmed on December 14, 2014 at 2:50 PM||comments (1)|
Applications are invited from outstanding Pakistani/AJK nationals for the award of PhD scholarships for University of New South Wales (UNSW), Australia. The scholarships will be awarded for academic session starting from February / March 2015.
The following documents are required to be submitted along with the prescribed application form:
1: Photocopy of confirmed admission letter for PhD Program at UNSW, Australia.
2: Attested photocopies of all educational testimonials by gazatted Govt. officer
3: Attested photocopy of CNIC
5: Attested photocopy of domicile
6: Statement of Purpose for pursuing higher studies (max. 500 words)
7: Research Proposal
8: Original online Deposit slip of Rs. 200/- (non-refundable) in favor of the Director General Finance, Higher Education Commission, H-9, Islamabad on account number 0112-00500119-01, HBL Aabpara Branch Islamabad as processing fee
a: Scholarships are tenable in all fields of study except Engineering, Agriculture and chemistry subjects
b: Candidates having admission in Criminology and related fields will be given preference.
c: Candidates having direct admission into PhD program will be considered. Admission in Master program will not be considered
d: Funding for a maximum period of 4 years will be provided for PhD program.
e: Awardees have to execute a bond with the HEC to serve in Pakistan for 5 years after completion of
f: study, preferably in an institution of Higher Education
g: Incomplete or applications received after due date will not be entertained
h: In-Service candidates should apply through proper channel
|Posted by shafiq ahmed on December 19, 2013 at 12:50 AM||comments (0)|
Soil organisms are responsible, to a varying degree depending on the system, for performing vital functions in the soil. Soil organisms make up the diversity of life in the soil (Figure A1.1). This soil biodiversity is an important but poorly understood component of terrestrial ecosystems. Soil biodiversity is comprised of the organisms that spend all or a portion of their life cycles within the soil or on its immediate surface (including surface litter and decaying logs) (Table A1.1) Soil organisms represent a large fraction of global terrestrial biodiversity. They carry out a range of processes important for soil health and fertility in soils of both natural ecosystems and agricultural systems. This annex provides brief descriptions of organisms that are commonly found in the soil and their main biological and ecological attributes. The community of organisms living all or part of their lives in the soil constitute the soil food web. The activities of soil organisms interact in a complex food web with some subsisting on living plants and animals (herbivores and predators), others on dead plant debris (detritivores), on fungi or on bacteria, and others living off but not consuming their hosts (parasites). Plants, mosses and some algae are autotrophs, they play the role of primary producers by using solar energy, water and carbon (C) from atmospheric carbon dioxide (CO2) to make organic compounds and living tissues. Other autotrophs obtain energy from the breakdown of soil minerals, through the oxidation of nitrogen (N), sulphur (S), iron (Fe) and C from carbonate minerals. Soil fauna and most fungi, bacteria and actinomycetes are heterotrophs, they rely on organic materials either directly (primary consumers) or through intermediaries (secondary or tertiary consumers) for C and energy needs. A food-web diagram shows a series of conversions (represented by arrows) of energy and nutrients as one organism eats another. The “structure” of a food web is the composition and relative numbers of organisms in each group within the soil. The living component of soil, the food web, is complex and has different compositions in different ecosystems. In a healthy soil, there are a large number of bacteria and bacterialfeeding organisms. Where the soil has received heavy treatments of pesticides, chemical fertilizers, soil fungicides or fumigants that kill these organisms, the beneficial soil organisms may die (impeding the performance of their activities), or the balance between the pathogens and beneficial organisms may be upset, allowing those called opportunists (disease-causing organisms) to become problems. FIGURE A1.1 The soil environment Source: S. Rose and E.T. Elliott TABLE A1.1 Categories and characteristics of soil organisms Category Characteristics Organisms Permanent Whole life cycle in the soil Mites, collembola, earthworms Temporal Part of life cycle in the soil Insect larvae Periodical Frequently enter into the soil Some insect larvae Transitory An inactive phase in the soil (e.g. eggs, pupae, hibernation) but the active period not in the soil Some insects Accidental Organisms fall down or they are drawn along Insect larvae The easiest and most widely used system for classifying soil organisms is by using body size and dividing them into three main groups: macrobiota, mesobiota and microbiota (Wallwork, 1970; Swift, Heal and Anderson, 1979). The ranges that determine each size group are not exact for all members of each group. MICRO-ORGANISMS These are the smallest organisms (<0.1 mm in diameter) and are extremely abundant and diverse. They include algae, bacteria, cyanobacteria, fungi, yeasts, myxomycetes and actinomycetes that are able to decompose almost any existing natural material. Micro-organisms transform organic matter into plant nutrients that are assimilated by plants. Two main groups are normally found in agricultural soils: bacteria and mycorrhizal fungi. Bacteria Bacteria are very small, one-celled organisms that can only be seen with a powerful light (1 000×) or electron microscope. They constitute the highest biomass of soil organisms. They are adjacent and more abundant near roots, one of their food resources. There are many types of bacteria but the focus here is on those that are important for agriculture, e.g. Rhizobium and actinomycetes. Bacteria are important in agricultural soils because they contribute to the carbon cycle by fixation (photosynthesis) and decomposition. Some bacteria are important decomposers and others such as actinomycetes are particularly effective at breaking down tough substances such as cellulose (which makes up the cell walls of plants) and chitin (which makes up the cell walls of fungi). Land management has an influence on the structure of bacterial communities as it affects nutrient levels and hence can shift the dominance of decomposers from bacterial to fungal. One group of bacteria is particularly important in nitrogen cycling. Free-living bacteria fix atmospheric N, adding it to the soil nitrogen pool; this is called biological nitrogen fixation and it is a natural process highly beneficial in agriculture. Other Nfixing bacteria form associations (in the form of nodules) with the roots of leguminous plants (Box A1.1). The nodule is the place where the atmospheric N is fixed by bacteria and converted into ammonium that can be readily assimilated by the plant. The process is rather complicated but, in general, the bacteria multiply near the root and then adhere to it. Next, small hairs on the root surface curl around the bacteria and they enter the root. Alternatively, the bacteria may enter directly through points on the root surface. Once inside the root, the bacteria multiply within thin threads. Signals stimulate cell multiplication of both the plant cells and the bacteria. This repeated division results in a mass of root cells containing many bacterial cells. Some of these bacteria then change into a form that is able to convert gaseous N into ammonium nitrogen (they can “fix” N). These bacteria are then called bacteroids and present different properties from those of free cells. Most plants need very specific kinds of rhizobia to form nodules. A specific Rhizobium species will form a nodule on a specific plant root, and not on others. The shapes that the nodules form are controlled by the plant and nodules can vary considerably in size and shape. BOX A1.1 Rhizobium and the nodulation process The nodulation process is a series of events in which rhizobia interact with the roots of legume plants to form a specialized structure called a root nodule. Different types of nodules on leguminous roots: (1) soybean; (2) alfalfa; (3) pea; and (4) white clover (Soltner, 1978). Source: FAO (2000) Actinomycetes are a broad group of bacteria that form thread-like filaments in the soil. The distinctive scent of freshly exposed, moist soil is attributed to these organisms, especially to the nutrients they release as a result of their metabolic processes. Actinomycetes form associations with some non-leguminous plants and fix N, which is then available to both the host and other plants in the near vicinity. Bacteria produce (exude) a sticky substance in the form of polysaccharides (a type of sugar) that helps bind soil particles into small aggregates, conferring structural stability to soils. Thus, bacteria are important as they help improve soil aggregate stability, water infiltration, and water holding capacity. However, in general their effect is less marked than that originated by large invertebrates such as earthworms. Fungi These organisms are responsible for the important process of decomposition in terrestrial ecosystems as they degrade and assimilate cellulose, the component of plant cell walls. Fungi are constituted by microscopic cells that usually grow as long threads or strands called hyphae of only a few micrometres in diameter but with the ability to span a length from a few cells to many metres. Soil fungi can be grouped into three general functional groups based on how they source their energy: *. Decomposers - saprophytic fungi - convert dead organic material into fungal biomass, CO2, and small molecules, such as organic acids. These fungi generally use complex substrates, such as the cellulose and lignin, in wood. They are essential for decomposing the carbon ring structures in some pollutants. Like bacteria, fungi are important for immobilizing
|Posted by shafiq ahmed on December 19, 2013 at 12:45 AM||comments (0)|
Experiment Is First to Simulate Warming of Arctic Permafrost Dec. 5, 2013— Although vegetation growth in the Arctic is boosted by global warming, it's not enough to offset the carbon released by the thawing of the permafrost beneath the surface, University of Florida researchers have found in the first experiment in the Arctic environment to simulate thawing of permafrost in a warming world. Share This: Twice as much carbon is frozen in Arctic permafrost as exists in the atmosphere today, and what happens to it as it thaws -- releasing greenhouse gases that fuel climate change -- is a key question, said professor Ted Schuur, who heads the Permafrost Carbon Network and the Ecosystem Dynamics Research Laboratory in the UF department of biology. Schuur, postdoctoral researcher Susan Natali and their team report the results of the three-year study in the journalEcology, released this week online. "The plants like it when they're warmer, so their growth is increasing, and if you just watch the tundra in the summertime and you look at the balance between what the plants are doing and what the soil is doing, the plants actually offset everything that happens in the soil. They're growing faster, getting bigger and taking carbon out of the air," Schuur said. "From the perspective of climate change, that's a good thing, tundra vegetation is making up for any carbon you're losing from the soil." The hitch? The Arctic's short summers do not make up for the long winters. Researchers are interested in the permafrost of the polar regions because these soils -- permanently frozen at great depths and for tens of thousands of years -- are vulnerable to global warming. "We continued to measure emissions in the winter, and what happens is the plants are shutting down, they're dormant, but the microbes continue to eat the soil, and it turns out that they release enough carbon during the winter to offset everything the plants gained in the summer, and possibly even more," Schuur said. As the experiment continues into the next three-year cycle, Schuur said he is looking for a point at which the plants hit a growth limit and stop absorbing more carbon, while the thawing permafrost continues to release carbon. Scientists estimate that 20 to 90 percent of the organic carbon pool in permafrost can be decomposed by microbes, converting it to greenhouse gases that warm the atmosphere. The warmer atmosphere causes additional thawing, creating a cycle that gets warmer and warmer. For the study, the research team built snow fences to create snowdrifts in the winter to warm the soil of the Alaskan tundra beneath. "This will be interesting for Floridians, but if you catch a whole bunch of snow in a giant pile, that actually keeps the tundra warmer than it would be," Schuur said. "It's like a giant blanket that insulates the tundra soils from the cold air." The extra snow, however, would cause an artificially late spring, and the research team needed to measure typical spring warming. "So we go up to Alaska and shovel all these drifts of snow away in April," Schuur said. "Alaskans think it's crazy." One of the successes of the experiment, Schuur said, was finding a way to model carbon release from permafrost in the environment on a year-round basis. Previous studies had used miniature greenhouses in summer months, but creating a warming situation in the winter was more challenging. "We wanted to warm the tundra and cause the permafrost to recede. This is the first experiment to isolate that effect in the field, so the first thing we show is that we're able to simulate what will happen in a future world when the permafrost degrades," Schuur said. Laboratory experiments, too, remain vitally important, Schuur said. A recent study in Nature Climate Change in which Schuur participated, examined 12 years of permafrost samples, an unusually long time frame for such studies. The research showed that the water content of the samples -- whether the soils drained or remained waterlogged -- had a large effect on how much carbon the soils released, with well-drained soils releasing more carbon. And in a recent report in Global Change Biology, Schuur and postdoctoral researcher Christina Schadel synthesized the data from sites across the Arctic Circle, as part of the Permafrost Carbon Network, started at UF by Schuur with a National Science Foundation grant. That study showed that the ratio of carbon to nitrogen in permafrost soils helps determine how much carbon the soil releases upon thawing. The ratio could be a useful tool in ecosystem modeling because the ratio could be measured in any soil sample. The studies confirm that a significant amount of carbon is released from thawing permafrost and highlight that there are factors beyond simply temperature that affect carbon release, Schuur said.