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Wang Q.,Southwest forestry University | Wang Q.,Beijing Forestry University | Zhang Y.,Southwest forestry University | Chen J.,Yunnan Academy of Forestry | And 2 more authors.
Beijing Linye Daxue Xuebao/Journal of Beijing Forestry University | Year: 2015

The aims of this study were to explore the distribution of Viscun articulatum in tea comunity and carry out a regression analysis of the factors affecting the distribution of V. articulatum based on the data of individual tea trees at the quadrat level. The results showed that 1) the mean rate of V. articulatum parasitism on tea trees was about 40%, and the frequency distribution of height for V. articulatum followed the ecological distribution while the number of branches was in the left skewed normal distribution, with most of them preferring to grow at 1/3-3/4 of the tree height. The distribution of V. articulatum depended more on tea tree characteristics than on environmental factors. 2) At single tea tree level, tea tree characteristics may have effect on the distribution of V. articulatum in the order of canopy > ground diameter > tree height > height under branch > mosses/lichen coverage. The tea trees with a high mosses/lichen coverage, large canopy, ground diameter ≥11 cm, height ≥3.1 m and HUD of 23-55 cm were found to be the most likely hosts of V. articulatum. 3) At the quadrat level, environmental factors affecting the distribution of V. articulatum were ranked as elevation > slope aspect > canopy density > slope degree. V. articulatum is mainly distributed in the study area at elevations higher than 1420 m, scarcely at mountain top or valleys. It was found to be more abundant in northwest and southeast slopes as well as in the areas with high canopy density. The greater the slope degree is, the better it grows. 4) Light and water were the dominant environmental factors affecting the distribution of V. articulatum, and the host community factors led to the reallocation of light and moisture, thus affecting the distribution position of V. articulatum in tea trees. © 2015, Beijing Forestry University. All right reserved. Source


Chen H.,CAS Kunming Institute of Botany | Chen H.,World Agroforestry Center East Asia Node | Yan M.,CAS Kunming Institute of Botany | Yan M.,World Agroforestry Center East Asia Node | And 8 more authors.
Journal of Hazardous Materials | Year: 2012

Successive surveys conducted in 1984, 2006 and 2007, of all villages in Yuanmou County, China, highlighted 40 villages with groundwater fluoride levels higher than 1.0. mg/L and related cases of human fluorosis. Using the data from these surveys and by employing geographic information system (GIS) techniques, high fluoride levels and fluorosis cases were mapped. The results show high fluoride concentrations and fluorosis hotspots were found to be predominately located in the lowlands of central Yuanmou County. Spatial distribution of high fluoride levels was found to be primarily determined by geology, arid climate, and topography. Both dental and skeletal fluorosis had dramatically decreased due to a program of low-fluoride drinking water supply supported by local governments. The prevalence of dental fluorosis in children had dropped from 43.26% in 1984 to 21.97% in 2006, and the number of skeletal fluorosis cases had decreased from 327 in 1984 to 148 in 2006, respectively. Despite a decline in fluorosis cases, the emergence of fluorosis in new areas indicates the need for both continuous monitoring of drinking water in affected areas and increased public awareness. © 2012 Elsevier B.V.. Source

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