The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Michael J. Lawes - One of the best experts on this subject based on the ideXlab platform.
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Ecological filtering by a dominant herb selects for shade tolerance in the tree seedling community of coastal dune forest
Oecologia, 2010Co-Authors: Zivanai Tsvuura, Megan E. Griffiths, Richard M. Gunton, Peter J. Franks, Michael J. LawesAbstract:The regeneration niche is commonly partitioned along a gradient from shade-tolerant to shade-intolerant species to explain plant community assembly in forests. We examined the shade tolerance of tree seedlings in a subtropical coastal forest to determine whether the ecological filtering effect of a dominant, synchronously monocarpic herb ( Isoglossa woodii ) selects for species at either end of the Light response continuum during the herb’s vegetative and reproductive phases. Photosynthetic characteristics of seedlings of 20 common tree species and the herb were measured. Seedlings were grown in the greenhouse at 12–14% irradiance, and their Light Compensation points measured using an open-flow gas exchange system. The Light Compensation points for the tree species were low, falling within a narrow range from 2.1 ± 0.8 μmol m^−2 s^−1 in Celtis africana to 6.4 ± 0.7 μmol m^−2 s^−1 in Allophylus natalensis , indicating general shade tolerance, consistent with a high and narrow range of apparent quantum yield among species (0.078 ± 0.002 mol CO_2 mol^−1 photon). Rates of dark respiration were significantly lower in a generalist pioneer species ( Acacia karroo ) than in a forest pioneer ( C. africana ), or in late successional phase forest species. We argue that the general shade tolerance, and phenotypic clustering of shade tolerance, in many tree species from several families in this system, is a result of ecological filtering by the prevailing low Light levels beneath the I. woodii understorey, which excludes most Light-demanding species from the seedling community.
Zivanai Tsvuura - One of the best experts on this subject based on the ideXlab platform.
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Ecological filtering by a dominant herb selects for shade tolerance in the tree seedling community of coastal dune forest
Oecologia, 2010Co-Authors: Zivanai Tsvuura, Megan E. Griffiths, Richard M. Gunton, Peter J. Franks, Michael J. LawesAbstract:The regeneration niche is commonly partitioned along a gradient from shade-tolerant to shade-intolerant species to explain plant community assembly in forests. We examined the shade tolerance of tree seedlings in a subtropical coastal forest to determine whether the ecological filtering effect of a dominant, synchronously monocarpic herb ( Isoglossa woodii ) selects for species at either end of the Light response continuum during the herb’s vegetative and reproductive phases. Photosynthetic characteristics of seedlings of 20 common tree species and the herb were measured. Seedlings were grown in the greenhouse at 12–14% irradiance, and their Light Compensation points measured using an open-flow gas exchange system. The Light Compensation points for the tree species were low, falling within a narrow range from 2.1 ± 0.8 μmol m^−2 s^−1 in Celtis africana to 6.4 ± 0.7 μmol m^−2 s^−1 in Allophylus natalensis , indicating general shade tolerance, consistent with a high and narrow range of apparent quantum yield among species (0.078 ± 0.002 mol CO_2 mol^−1 photon). Rates of dark respiration were significantly lower in a generalist pioneer species ( Acacia karroo ) than in a forest pioneer ( C. africana ), or in late successional phase forest species. We argue that the general shade tolerance, and phenotypic clustering of shade tolerance, in many tree species from several families in this system, is a result of ecological filtering by the prevailing low Light levels beneath the I. woodii understorey, which excludes most Light-demanding species from the seedling community.
S. C. Thomas - One of the best experts on this subject based on the ideXlab platform.
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Physiological and morphological correlates of whole-plant Light Compensation point in temperate deciduous tree seedlings
Oecologia, 2007Co-Authors: J. L. Baltzer, S. C. ThomasAbstract:A range of traits, including metabolic costs, biomass allocation and seed reserves, may contribute to interspecific variation in the shade tolerance of tree seedlings. In addition, shade tolerance may be affected by differential responses of species to soil resource availability at low Light. We used a custom-built whole-plant gas-exchange chamber to quantify instantaneous whole-plant Light Compensation point (WPLCP) and to parameterize whole-plant daily C gain models for seedlings of eight temperate deciduous tree species. We examined the relationship of WPLCP to growth, biomass allocation and gas-exchange under high and low Light and nutrient availabilities and compared it to WPCLP of naturally recruited saplings. For species showing a response, both increased Light and nutrient availability resulted in increased WPLCP. However, species’ responses to resource availability did not correspond closely with shade tolerance as has generally been predicted. Variation in WPLCP within species was best predicted by whole-plant dark respiration rates, leaf-level Light Compensation point and leaf mass per area. Among species, seed size was a strong negative correlate of WPLCP, explaining 66% of the variation. Species with the lowest WPLCP maintained lower growth rates across treatments but greater biomass in the low-Light treatment compared with more Light-demanding species. These data suggest that a number of traits, in particular metabolic costs and seed size, contribute to WPLCP. However, gas-exchange-based WPLCP was 1.5–3.5 times lower than corresponding growth-based field estimates of WPLCP, suggesting that other factors such as biotic interactions or ontogenetic shifts in whole-plant Light requirements may substantially increase species’ WPLCP under natural conditions.
Jyh Jong Tang - One of the best experts on this subject based on the ideXlab platform.
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Segmentation and grading of eczema skin lesions
2014 8th International Conference on Signal Processing and Communication Systems (ICSPCS), 2014Co-Authors: Humaira Nisar, Kim Ho Yeap, Jyh Jong TangAbstract:In this paper Eczema skin lesions are segmented and graded using image processing and analysis. For preprocessing adaptive Light Compensation and gamma correction has been used. The effect of color space normalization has been studied for lesion segmentation. K-means algorithm is used for segmentation. We have used RGB and CIELab color models; and their normalized I and II versions. The experimental results show that normalized color spaces give better segmentation results than the normal color spaces. Our proposed algorithm gives best segmentation accuracy of 84.6% for RGB normalized II color space for the G channel for adaptive Light Compensation. The grading accuracy for erythema is around 70%.
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A two level k-means segmentation technique for eczema skin lesion segmentation using class specific criteria
2014 IEEE Conference on Biomedical Engineering and Sciences (IECBES), 2014Co-Authors: Humaira Nisar, Jyh Jong TangAbstract:In the paper we have proposed a two level k-means segmentation technique for eczema skin lesion segmentation. Two class criteria is used for classifying the normal skin and eczema skin lesions using Mahalanobis distance. In order to further improve the segmentation performance normalized color spaces are used. Our experiments include RGB and CIElab color models; and their color space normalized-I (CSN-I) versions. For pre-processing Frankle-McCann retinex and adaptive Light Compensation is used. The experimental results show that our proposed algorithm gives better results with normalized color spaces. We have achieved a segmentation accuracy of 86.07% for RGB normalized I color space for the G channel with adaptive Light Compensation.
Megan E. Griffiths - One of the best experts on this subject based on the ideXlab platform.
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Ecological filtering by a dominant herb selects for shade tolerance in the tree seedling community of coastal dune forest
Oecologia, 2010Co-Authors: Zivanai Tsvuura, Megan E. Griffiths, Richard M. Gunton, Peter J. Franks, Michael J. LawesAbstract:The regeneration niche is commonly partitioned along a gradient from shade-tolerant to shade-intolerant species to explain plant community assembly in forests. We examined the shade tolerance of tree seedlings in a subtropical coastal forest to determine whether the ecological filtering effect of a dominant, synchronously monocarpic herb ( Isoglossa woodii ) selects for species at either end of the Light response continuum during the herb’s vegetative and reproductive phases. Photosynthetic characteristics of seedlings of 20 common tree species and the herb were measured. Seedlings were grown in the greenhouse at 12–14% irradiance, and their Light Compensation points measured using an open-flow gas exchange system. The Light Compensation points for the tree species were low, falling within a narrow range from 2.1 ± 0.8 μmol m^−2 s^−1 in Celtis africana to 6.4 ± 0.7 μmol m^−2 s^−1 in Allophylus natalensis , indicating general shade tolerance, consistent with a high and narrow range of apparent quantum yield among species (0.078 ± 0.002 mol CO_2 mol^−1 photon). Rates of dark respiration were significantly lower in a generalist pioneer species ( Acacia karroo ) than in a forest pioneer ( C. africana ), or in late successional phase forest species. We argue that the general shade tolerance, and phenotypic clustering of shade tolerance, in many tree species from several families in this system, is a result of ecological filtering by the prevailing low Light levels beneath the I. woodii understorey, which excludes most Light-demanding species from the seedling community.