16,134 research outputs found
Seed and seedling responses to inoculation with mycorrhizal fungi and root nodule bacteria: implications for restoration of degraded Mediterranean-type Tuart woodlands
Inoculation with beneficial soil microorganisms has the potential to enhance success of restoration, particularly in harsh Mediterranean-type ecosystems (MTEs). We investigated the effects of microorganisms (mycorrhizal fungi and root nodule bacteria) and planting material (seed and nursery-raised seedlings) on early establishment and growth of two key postdisturbance colonizing species with different life histories, life forms and functional types (Eucalyptus gomphocephala and Acacia saligna) under field conditions. Establishment and growth were monitored at 13months, following the first MTE drought period. For E. gomphocephala, establishment was higher for seedlings (81%) than for seeding (7.5%). Inoculation with ectomycorrhizal fungal spores was not beneficial. For A. saligna, establishment was also higher for seedlings (84%) than for seeding (42.5%). Mycorrhizal fungal inoculum had no effect on establishment or growth. This study has shown that in harsh MTE conditions, the use of seedlings is more effective than seeding in degraded woodlands even when attempting to reintroduce key colonizing species. The microorganism treatments tested did not result in significant improvement in establishment or growth
Formal Context Generation using Dirichlet Distributions
We suggest an improved way to randomly generate formal contexts based on
Dirichlet distributions. For this purpose we investigate the predominant way to
generate formal contexts, a coin-tossing model, recapitulate some of its
shortcomings and examine its stochastic model. Building up on this we propose
our Dirichlet model and develop an algorithm employing this idea. By comparing
our generation model to a coin-tossing model we show that our approach is a
significant improvement with respect to the variety of contexts generated.
Finally, we outline a possible application in null model generation for formal
contexts.Comment: 16 pages, 7 figure
Restoring degraded woodlands
In many places on the Swan Coastal Plain Eucalyptus gomphocephala (tuart) woodlands are in decline or are degraded (Bulletin 1). This occurs for many reasons, including grazing by stock, weed invasion, logging and clearing. It is often a combination of these factors that gradually lead to a decline in the tuart populations
Recommended from our members
Evaluating the psychometric properties of the multigroup ethnic identity measure (MEIM) within the United Kingdom
In the present study, we examined the psychometric properties of the Multigroup Ethnic Identity Measure (MEIM) (Phinney, 1992; Phinney & Alipuria, 1990) among an ethnically diverse sample within the United Kingdom. In initial analyses, we evaluated the goodness-of-fit of a one-factor model (i.e., global ethnic identity) and the goodness-of-fit of a two-factor model (i.e., correlated but distinct Exploration and Commitment components). Results of initial confirmatory factor analyses led us to reject both the one-factor and two-factor models. Results of subsequent exploratory and confirmatory factor analyses revealed a three-factor structure (i.e., correlated but distinct Behavioral, Cognitive, and Affective components of ethnic identity) among the sample as a whole (n = 234) and among Asian Indian persons (n = 88) in particular, though resulst were mixed among White U.K./Irish persons (n = 54) in particular. Implications for the study of ethnicity-related concepts in the incerasibgly multi-cultural U.K. are discussed
Gravitational energy from a combination of a tetrad expression and Einstein's pseudotensor
The energy-momentum for a gravitating system can be considered by the tetard
teleparalle gauge current in orthonormal frames. Whereas the Einstein
pseudotensor used holonomic frames. Tetrad expression itself gives a better
result for gravitational energy than Einstein's. Inspired by an idea of Deser,
we found a gravitational energy expression which enjoys the positive energy
property by combining the tetrad expression and the Einstein pseudotensor,
i.e., the connection coefficient has a form appropriate to a suitable
intermediate between orthonormal and holonomic frames.Comment: 5 page
Extended Optical Model Analyses of Elastic Scattering and Fusion Cross Section Data for the C+Pb System at Near-Coulomb-Barrier Energies by using a Folding Potential
Simultaneous analyses are performed for elastic scattering and
fusion cross section data for the C+Pb system at
near-Coulomb-barrier energies by using the extended optical model approach in
which the polarization potential is decomposed into direct reaction (DR) and
fusion parts. Use is made of the double folding potential as a bare potential.
It is found that the experimental elastic scattering and fusion data are well
reproduced without introducing any normalization factor for the double folding
potential and also that both DR and fusion parts of the polarization potential
determined from the analyses satisfy separately the dispersion
relation. Furthermore, it is shown that the imaginary parts of both DR and
fusion potentials at the strong absorption radius change very rapidly, which
results in a typical threshold anomaly in the total imaginary potential as
observed with tightly bound projectiles such as -particle and O.Comment: 26 pages, 7 figures, submitted to Physical Review
C1-C8 volatile organic compounds in the atmosphere of Hong Kong: Overview of atmospheric processing and source apportionment
We present measurements of C1-C8 volatile organic compounds (VOCs) at four sites ranging from urban to rural areas in Hong Kong from September 2002 to August 2003. A total of 248 ambient VOC samples were collected. As expected, the urban and sub-urban sites generally gave relatively high VOC levels. In contrast, the average VOC levels were the lowest in the rural area. In general, higher mixing ratios were observed during winter/spring and lower levels during summer/fall because of seasonal variations of meteorological conditions. A variation of the air mass composition from urban to rural sites was observed. High ratios of ethyne/CO (5.6 pptv/ppbv) and propane/ethane (0.50 pptv/pptv) at the rural site suggested that the air masses over the territory were relatively fresh as compared to other remote regions. The principal component analysis (PCA) with absolute principal component scores (APCS) technique was applied to the VOC data in order to identify and quantify pollution sources at different sites. These results indicated that vehicular emissions made a significant contribution to ambient non-methane VOCs (NMVOCs) levels in urban areas (65±36%) and in sub-urban areas (50±28% and 53±41%). Other sources such as petrol evaporation, industrial emissions and solvent usage also played important roles in the VOC emissions. At the rural site, almost half of the measured total NMVOCs were due to combustion sources (vehicular and/or biomass/biofuel burning). Petrol evaporation, solvent usage, industrial and biogenic emissions also contributed to the atmospheric NMVOCs. The source apportionment results revealed a strong impact of anthropogenic VOCs to the atmosphere of Hong Kong in both urban/sub-urban and rural areas. © 2006 Elsevier Ltd. All rights reserved
- âŠ