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  • Polymer and Materials Science  (2)
  • 15N  (1)
  • amenity plantings  (1)
  • 1
    ISSN: 1572-9680
    Keywords: silvopastoral ; shelterbelts ; woodlots ; amenity plantings ; erosion control ; conservation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Agroforestry in Australia and New Zealand is dominated by silvopastoralism. Farmers may employ combinations of shelterbelts, shade trees, widely spaced trees over pasture, or more densely planted woodlots. In addition to wood production and shelter, erosion control, amenity and landscape planting, and conservation of natural forest are often important. Many farm forestry people show considerable innovation. In temperate wetter areas of Australia, eucalyptus and, to a lesser extent,Pinus radiata (radiata pine) dominate agroforestry tree plantings for wood, shade, shelter, and salinisation and erosion prevention. The One Billion Tree Program, initiated by the Australian Federal Government, provides limited funding for tree planting. Joint farmer ventures with the State or local industry are also common. Most State governments also provide advice, and planting is tax deductible. Local landcare groups, formed to encourage sustainable agriculture, often promote tree planting, particularly where soil degradation is a problem. Melbourne University and other Techncial Institutes offer training in agroforestry. In New Zealand, a third of the farms require trees for soil conservation. This, together with the growing recognition of the financial benefits of planting trees, has resulted in small landowners doing most of the current planting of 80,000 to 100,000 ha yr−1. Most farmers plant radiata pine, but eucalyptus and other hardwoods, including willows and poplars, are also widely used. There are almost no government incentives for tree planting in New Zealand. The Farm Forestry Association is the major extension organization. Lincoln University has an important teaching and research commitment, and the New Zealand Forest Research Institute Limited has developed very useful management models.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-9680
    Keywords: nitrogen fixation ; 15N ; %Ndfa ; ryegrass+clover pasture ; silvopastoral system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Quantitative field measurements of biological nitrogen fixation (BNF) and biomass production by four different understorey pastures in a Pinus radiata-pasture agroforestry system were determined over a period of one year. The trees were two years old at the beginning of this study and the understorey pastures were being cut and removed for silage. The BNF was determined using the 15N dilution technique. Pastures of ryegrass+clover, cocksfoot+clover, phalaris+clover and lucerne were used. Substantial amounts of BNF were found (71 to 230 kg N ha−1 year−1) with lucerne showing the highest N fixation. However, lucerne derived only 71 to 72% of its N from the atmosphere (%Ndfa) during the spring/summer period compared to 83–97% with clovers, thus the net N demand from the soil was substantially higher with lucerne. This caused increased N stress to the trees. Clover in ryegrass+clover pasture fixed more N than the other grass+clover pastures. Although pasture position in relation to trees did not affect annual pasture total DMY and %Ndfa, pastures north of tree row grew better than those in other positions. Trees significantly affected the BNF of legumes and the botanical composition of pastures with highest BNF and legume production occurring in pastures midway between two rows of trees. These results suggest that it would be advantageous to evaluate different legumes and grasses for tolerance of shade and moisture stress in future studies. As the trees studied were only 1.5 to 3 m in height, their effects on BNF, seasonal pasture biomass production and botanical composition are expected to increase with tree dominance in the ecosystem with time. Amounts of N fixed were related to the productivity (i.e. dry matter and N yield) and seasonal persistence of the legumes. The productivity was high in spring and summer and low in autumn and winter.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 29 (1991), S. 1271-1285 
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Predictions of the rheological properties of concentrated isotropic solutions of stiff polymers are made that improve on those obtained with the approximate Doi theory. Predictions of the shear-rate and concentration dependence of the viscosity η and the first and second normal stress differences N1 and N2 that avoid the closure approximations of Doi are obtained by using a Galerkin numerical solution for the orientation distribution function. The predictions for η and N1, though they neglect the effects of polydispersity in molecular weight, are shown to be in quantative agreement with recent measurements on solutions of poly-γ-benzyl-L-glutamate (PBLG). The polydispersities of a series of commercial PBLG and PBDG samples are measured by gel permeation chromatography, and found to be broad. An attempt is made to account for the effects of polydispersity on the linear viscoelastic storage and loss moduli for PBLG solutions by using the Marrucci-Grizzuti extension of the Doi theory. The attempt fails. The most probable explanation for the failure is that the rotary diffusive motions of the shorter molecules in the mixture are drastically slowed by the matrix of surrounding longer molecules.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 57 (1995), S. 151-173 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Homogeneous and nonhomogeneous reactive extrusion of polypropylene is modeled using random chain scission statistics coupled with the double reptation mixing rule. In this manner, the evolution of both the molecular weight distribution and the linear viscoelastic material properties is quantitatively predicted for the reactive extrusion-pelletization process. Dispersion in the level of random chain scission has little impact on the MFI for a given average level of chain scission; however, dispersion does generate a marked increase in the recoverable compliance (melt elasticity) relative to the ideal homogeneous random chain scission case. Methods to quantitatively determine the degree of cracking dispersion in processing equipment are identified. Quality control issues such as blending materials of known linear viscoelastic properties to obtain a desired property set is considered in the context of known empirical relations consistent with the double reptation model. Simple mixing rules for the melt flow index and the steady-state recoverable compliance involving only single component MFI and Je information are derived. © 1995 John Wiley & Sons, Inc.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
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