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481.
In the frost‐prone, summer dominant rainfall zone of northern NSW and southern Queensland, sown tropical grass pastures commonly establish with plant densities >26 plants per m2, yet the optimum density for maximum herbage accumulation and hydrological performance is not known. A replicated, field study was established in northern NSW in November 2011, using five densities of Digitaria eriantha (digit grass): 0, 1, 4, 9 and 16 plants per m2 and a range of agronomic and hydrologic measures was assessed. The results showed that the largest differences between plant densities in herbage accumulation, root depth, soil water extraction and rainfall refill efficiency occurred during the first 2 years; after this time, digit grass pastures with densities of ≥4 plants per m2 responded similarly. Plant frequency increased with increasing plant density but the treatments did not converge. During the first two growing seasons, there was no effect of plant density on water use efficiency; however, by the third growing season, pastures with 4 plants per m2 were the most water efficient. Overall, the results indicated that 1 plant per m2 was too low to efficiently use resources, 16 plants per m2 utilized the resources quickly then tended to stall, while 4–9 plants per m2 was a good compromise between agronomic and hydrological response, achieving both herbage accumulation and sustainability goals. A practical management advantage of pastures with 4–9 plants per m2 is they allow soil water resources to be available for a longer period of time and potentially provide the opportunity to establish legumes in the ensuing 24‐month period. 相似文献
482.
Zhou Yongchun Zhang Wenbo Cheng Xilei Harris Warwick Schaeffer Sean M. Xu Xinyang Zhao Bing 《Journal of Soils and Sediments》2019,19(5):2190-2199
Journal of Soils and Sediments - Soil organic carbon (SOC) dynamics are central to understanding the effects of environmental change on the carbon cycle of ecosystems. Vegetation and soil stable... 相似文献
483.
The soluble fiber, β‐glucan, in oat products is an active hypolipidemic component that is responsible for lowering plasma lipids. Quantitative analysis of β‐glucan in oat hydrocolloids such as Oatrim, Nutrim, and C‐Trim was performed to measure the total β‐glucan content and molecular weight distribution. For the measurement of total β‐glucan content, both modified flow‐injection analysis (FIA) method and the standard AACC enzymatic method were employed. FIA method uses the enhanced fluorescence produced when β‐glucan forms complexes with Calcofluor. Experimental results of both the modified FIA method and the standard AACC enzymatic method revealed very good coincidence with each other. This result confirms the applicability of either technique for the quantitative evaluation of β‐glucan in hydrocolloids. Molecular weight (MW) distribution of β‐glucan was determined by size‐exclusion chromatography with postcolumn detection. Experimental results revealed that the molecular weight of β‐glucan in the Trim products was decreased during the manufacturing process. This result was ascribed to the rigorous processing condition of jet‐cooking. 相似文献
484.
Heavy atmospheric nitrogen (N) deposition has been associated with altered nutrient cycling, and even N saturation, in forest ecosystems previously thought to be N-limited. This observation has prompted application to such forests of non-N mineral nutrients as a mitigation measure. We examined leaf gas-exchange, leaf chemistry and leaf and shoot morphological responses of Acer saccharum Marsh. saplings and mature trees to experimental additions of non-nitrogenous mineral nutrients (dolomitic lime, phosphorus + potassium (P + K) and lime plus P + K) over 2 years in the Haliburton region of central Ontario, which receives some of the largest annual N inputs in North America. Nutrients were adsorbed in the mineral soil and taken up by A. saccharum trees within 1 year of fertilizer application; however, contrary to expectation, liming had no effect on soil P availability. Saplings and canopy trees showed significant responses to both P + K fertilization and liming, including increased foliar nutrient concentration, leaf size and shoot extension growth; however, no treatment effects on leaf gas-exchange parameters were detected. Increases in shoot extension preceded increases in diameter growth in saplings and canopy trees. Vector analysis of shoot extension growth and nutrient content was consistent with sufficiency of N but marked limitation of P, with co-limitation by calcium (Ca) in saplings and by Ca, Mg and K in canopy trees. 相似文献
485.
486.
Shabbar Jaffry Sean Pascoe George Taylor Unax Zabala 《Aquaculture Economics & Management (Blackwell Science)》2013,17(3-4):157-167
Abstract The introduction and rapid expansion of farmed salmon production in the mid 1980s has transformed the international market for salmon. Spain is one of the most important markets for fish within Europe and the world, and has seen a substantial increase in its demand for salmon. As in other European countries, this has raised concerns that the increased supply of salmon to Spain may have detrimental effects on the market prices of traditional (wild‐caught) species. In this paper, the extent to which salmon competes with the main traditional fish species in the Spanish market is examined using market delineation methodologies. In particular, the potential interactions between species is examined in a multivariate cointegration framework. The results suggest that salmon is at best only a weak substitute for tuna, hake and whiting, but no significant interaction could be found. 相似文献
487.
Chan Sol Kang Ho Jin Yoon Choong Hee Hong Sun Jin Kwon Hyun Sun Kim Doo Hyun Baik 《Fibers and Polymers》2015,16(12):2513-2518
A series of copolyesters (Co-PETs) containing poly(ethylene glycol) (PEG), 5-sodiumsulfodimethyl isophthalate (DMS), and dimethyl isophthalate (DMI) were synthesized via the conventional two-step melt-polycondensation method. The synthesized Co-PETs were characterized by 1H-NMR spectroscopy, FT-IR spectroscopy, differential scanning calorimeter (DSC), and thermogravimetric analyzer (TGA). The DSC results showed that the melting temperature (T m) and the heats of fusion (ΔH m) of Co-PETs decreased with increasing the DMS content in Co-PET, while the inclusion of PEG did not affect their thermal properties significantly. The water absorption and the water contact angle of the Co-PET films were found to be significantly affected by the DMS content rather than PEG content. The moisture-related cooling properties of the fabric samples made of Co-PET 5 as well as PET were evaluated by using liquid moisture management tester (MMT) and Q max measurements. The MMT and Q max results indicated that Co-PET 5 fabric containing DMS 1.0 mol% and PEG 10.0 wt% in Co-PET seemed to be a good candidate for the fabric having durable cooling effects. 相似文献
488.
Melony J Sellars Leanne Dierens Sean McWilliam Bryce Little Brian Murphy Greg J Coman William Barendse John Henshall 《Aquaculture Research》2014,45(3):417-426
Custom‐built single‐nucleotide‐polymorphism (SNP) marker systems that are compatible with Sequenom® chemistry are compared with a general purpose microsatellite marker system in their ability to accurately assign Black Tiger shrimp parentage. The microsatellite system consisted of 13 markers, while the SNP systems comprised of 63 (SNPa), 59 (SNPb) or 122 markers (SNPab). Comparisons were made using animals from commercial breeding lines with thresholds for assignment derived using simulated genotypes. Pedigree assignment for commercial lines was highest when panel SNPab was used. Panel SNPa, panel SNPb and Msat functioned with an overall similar level of power for pedigree assignment, however, for some families, the Msat panel was not as powerful. Pedigree assignment for the simulated diploid genotypes was higher for all SNP panels compared with Msat. Overall the three SNP panels provided parentage assignment rates suitable for commercial shrimp breeding programs with assignment rates in the simulated genotypes greater than 96.8% and correct assignments greater than 99.3%. Compared with the microsatellite panel, custom‐built SNP panels, whether they operate as single panels, or as a combined panel, have improved power to perform dam and sire assignment to progeny and provide faster turnaround time as they are compatible with Sequenom® chemistry. 相似文献
489.
Group selection silviculture creates canopy openings that can alter connectivity in patchy forests, thereby affecting wildlife
movement and fire behavior. We examined effects of group selection silviculture on percolation (presence of continuously forested
routes across a landscape) in Sierra Nevada East-side pine forest in northern California, USA. Four ~ 250 ha project areas
were analyzed at three map resolutions in three ways: analyzing forest cover maps for percolation before and after group-selection
treatment, placing simulated group openings in forest cover maps until fragmentation occurred, and comparing project areas
to neutral maps that varied in forest cover and self-adjacency. Two project areas were fragmented (i.e., did not percolate)
prior to treatment, one resisted fragmentation, and the other became fragmented by treatment when analyzed at 30 m cell resolution.
Median simulated openings required to create fragmentation agreed well with the actual number. There was a well-defined transition
between percolating and non-percolating neutral maps; increased aggregation of forest lowered the critical value at which
forests percolated. A logistic model based on these maps predicted percolation behavior of the project areas effectively,
but alternative generating algorithms gave slightly different predictions. A graph of this model provides a straightforward
way to visualize how close a landscape is to fragmentation based on its forest cover and aggregation. In East-side Sierran
landscape, fragmentation from group-selection openings may make the landscape less hospitable to the American marten but more
resistant to crown fire. 相似文献
490.