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151.
The characteristics of species diversity in Cupressus funebris secondary forest under the effect of geological hazard were explored by selecting the typical landslide surface of Fenghuang Mountain, Leigu Town, Beichuan County, which was derived from the 5.12 Wenchuan earthquake. The results showed that 93 species belonged to 42 families, and 78 genera were found in the landslide area, where the main families were Compositae, Leguminosae, and Gramineae-based. Further, 97 species in the transition area belonged to 39 families and 80 genera, and the main families were Compositae, Gramineae, and Rosaceae-based. In all, 108 species were recorded in the non-landslide area, which belonged to 59 families and 92 genera, the main families of which were Compositae, Rosaceae, and Gramineae-based. Compositae and Gramineae played important roles in the landslide recovery process after earthquake. The Pielou index (JSW) was the highest in the non-landslide area of the herb layer, whereas the richness index (D) was the lowest; the Shannon-Wiener index (H) and Simpson index (H') showed medium values. In the non-landslide area, the D, H, and H' were the highest in the shrub layer, whereas the JSW was the lowest. Further, the species diversity index of the transitional area was higher than that of the landslide area. In the tree layer, the D and H were both the highest and lowest in the landslide area and transition area, respectively. In contrast, the H' and JSW were the highest in the transition area and the lowest in the non-landslide area. The distribution of vegetation was generally consistent with the distribution of soil nutrients in the spatial distribution of surface soil nutrients. The succession of trees in the landslide area was relatively slow and at the initial stage, and the pioneer species were Coriaria nepalensis, Leptopus chinensis, and Arthraxon lanceolatus in this area. Taken together, the findings suggested that the stability of a plant community can be increased by improving the soil and stabilizing the slope. © 2018 Science Press. All rights reserved. 相似文献
152.
在研制的室内模型箱中,进行不同筋材配筋率和铺筋层数下加筋土挡墙模型试验,不同拉拔速度筋-土界面原位拉拔试验,分析了配筋率和铺筋层数对加筋土挡墙变形及土压力的影响及拉拔速度对筋-土界面抗剪强度的影响。结果表明,挡墙顶部沉降在筋材与面板连接处及挡墙后部较大,挡墙中间部位沉降较小。随着配筋率和铺筋层数的增加,挡墙顶部沉降和刚性面板倾角变小,面板受到的土压力减小。加筋土挡墙最优配筋率为60%~70%。拉拔速度对筋-土界面黏聚力几乎没有影响,但筋-土界面摩擦角随着拉拔速度的增加有增大趋势,从而导致筋-土界面的抗剪强度增大。 相似文献
153.
基于辽宁省56个气象站的气象资料,利用Kira的温暖指数(WI)、寒冷指数(CI)和徐文铎的湿度指数(HI)分析辽宁省近40年(1967-2006年)气候-植被指标的时空变异。结果表明,就辽宁省区域平均值而言,WI指数呈升高趋势,每10年增加幅度为2.47℃·月,CI指数呈下降趋势,每10年下降幅度为2.31℃·月,HI总体呈下降趋势,波动较WI和CI明显,从气候—植被指数变化趋势看,对红松Pinus koraiensis Sieboldet Zuccarini、长白落叶松Larixolgensis等不利,而对油松Pinu stabulaeformis Carr、栓皮栎Quercus vari abilis Blume等树种有利。空间变化特征表现为,温暖指数界限呈向西北移动的趋势,表明暖温带落叶阔叶疏林带的适宜面积增加,而温带针阔叶混交林带的适宜面积减小;HI指数减小并且向东移,表明随着指数带的北移和东移缩小限制了原有针叶树种的生长,而对栎树Phytophthora ramorum等阔叶树种有利。 相似文献
154.
155.
Chung-Yi Chung Jen-Jeng Chen Chang-Gai Lee Chun-Yen Chiu Wen-Liang Lai Shao-Wei Liao 《Environmental monitoring and assessment》2011,173(1-4):499-517
This work investigated sediment samples collected from Dapeng Bay and three neighboring rivers (Kaoping River, Tungkang River, and Lingbeng River) in southwestern Taiwan, Republic of China. Multivariate statistical analysis techniques, i.e., factor analysis, cluster analysis, and canonical discriminant analysis were used for the evaluation of spatial variations to determine the types of pollution and to identify pollutant sources from neighboring rivers. Factor analysis results showed that the most important latent factors in Dapeng Bay are soil texture, heavy metals, organic matter, and nutrients factors. Contour maps incorporating the factor scores showed heavy metals accumulate along the lakesides, especially on the southeastern banks of the lakes. A cluster analysis was performed using factor scores computed from these latent factors. We then classified these areas into five distinct classes using sampling stations, and we illustrate that in the three river classes, the sediment properties are influenced by industrial and domestic wastewater and agricultural activities (including livestock rearing and farm activities). However, in Dapeng Bay, the rivers were influenced more by complicated biogeochemical processes; these could be identified as a type of pollution. Canonical discriminant analysis illustrated that two constructed discriminant functions made a marked contribution to most of the discriminant variables, and the significant parameters of porosity and Cd, Cr, Al, and Pb content were combined as the ??heavy metal factor??. The recognition capacities of the two discriminant functions were 82.6% and 17.4%, respectively. It is also likely that the annual mean of the water exchange rate is insufficient (taking about 7 days to eliminate pollutants) and therefore has significantly influenced the carbon and nutrient biogeochemical processes and budgets in the semi-enclosed ecosystem. Thus, the sediment properties are not similar between the lagoon and the neighboring rivers. Our results yield useful information concerning estuary recovery and water resources management and may be applicable to other basins with similar characteristics that are experiencing similar coastal environmental issues. 相似文献
156.
Chung-Yi Chung Pei-Ling Chung Shao-Wei Liao 《Environmental monitoring and assessment》2011,173(1-4):701-707
In the land ecosystem, the forest can absorb the carbon dioxide (CO2) in the atmosphere and turn the CO2 into organic carbon to store it in the plant body. About 2 × 1011 tons of CO2 changes through photosynthesis into organic matter by plant annually. In this research, ten kinds of woody plants were selected for assessing the carbon fixation ability influenced by sulfur dioxide (SO2). The tested trees were put into a fumigation chamber for 210 days in a 40-ppb SO2 environment. The results of this study showed that there was no clear symptom of tested trees under a 40-ppb SO2 environment. The tested trees could tolerate this polluted environment, but it will impact their CO2 absorption ability. The carbon fixation ability will reduce as the polluted period lengthens. The carbon fixation potential of tested trees ranged from 2.1 to 15.5 g·CO2/m2·d with an average of 7.7 g·CO2/m2·d. The changes in CO2 absorption volume for Messerschmidia argentea were more stable during the fumigation period with a variation of 102%. Among the tested trees, Diospyros morrisiana had the best carbon fixation potential of 9.19 g·CO2/m2·d and M. argentea had the least with 2.54 g·CO2/m2·d. 相似文献
157.
Changes in the area of inland lakes in arid regions of central Asia during the past 30 years 总被引:5,自引:0,他引:5
Jie Bai Xi Chen Junli Li Liao Yang Hui Fang 《Environmental monitoring and assessment》2011,178(1-4):247-256
Inland lakes are major surface water resource in arid regions of Central Asia. The area changes in these lakes have been proved to be the results of regional climate changes and recent human activities. This study aimed at investigating the area variations of the nine major lakes in Central Asia over the last 30 years. Firstly, multi-temporal Landsat imagery in 1975, 1990, 1999, and 2007 were used to delineate lake extents automatically based on Normalized Difference Water Index (NDWI) threshold segmentation, then lake area variations were detailed in three decades and the mechanism of these changes was analyzed with meteorological data and hydrological data. The results indicated that the total surface areas of these nine lakes had decreased from 91,402.06 km2 to 46,049.23 km2 during 1975?C2007, accounting for 49.62% of their original area of 1975. Tail-end lakes in flat areas had shrunk dramatically as they were induced by both climate changes and human impacts, while alpine lakes remained relatively stable due to the small precipitation variations. With different water usage of river outlets, the variations of open lakes were more flexible than those of other two types. According to comprehensive analyses, different types of inland lakes presented different trends of area changes under the background of global warming effects in Central Asia, which showed that the increased human activities had broken the balance of water cycles in this region. 相似文献
158.
Averrhoa carambola L., a high-biomass tropical tree, has recently been shown to be a strong accumulator of cadmium (Cd) and has great potential for Cd phytoextraction. In the present study, field studies and a controlled-environment experiment were combined to establish the extent of variation in Cd tolerance and accumulation at the cultivar level using 14 to 19 cultivars of A. carambola. The results indicated that all cultivars tested could accumulate Cd at high but different levels, and that Cd tolerance also varied greatly between these cultivars. It is confirmed that the high Cd tolerance and accumulation capacity are species-level and constitutional traits in A. carambola. However, no correlation was detected between tolerance index and accumulation of Cd in different cultivars, suggesting that the two traits are independent in this woody Cd accumulator. More importantly, cultivar Wuchuan Sweet (WCT) was shown to have the highest Cd-extraction potential; it yielded a high shoot biomass of 30 t ha(-1) in 230 d, and extracted 330 g ha(-1) Cd in the aerial tissues grown in Cd-contaminated field soil, which accounted for 12.8% of the total soil Cd in the top 20 cm of the soil profile. 相似文献
159.
Yang SX Li JT Yang B Liao B Zhang JT Shu WS 《Journal of environmental monitoring : JEM》2011,13(7):1876-1883
Previous studies have shown that the application of soil amendments is efficient in reducing acidity and heavy metal bioavailability in mine soils. However, it remains a challenge for environmentalists to predict accurately and control economically the re-acidification in re-vegetated mine soils. In this study, net acid generation (NAG) test and bioassay technique were employed to assess the effectiveness of the amendments [including lime, N-P-K (nitrogen, phosphorous and potassium) fertilizer, phosphate and river sediment] on re-acidification and heavy metal immobilization in an extremely acid (pH < 3) mine soil. Our results suggested that NAG test was a rapid and accurate approach to assess the effectiveness of the amendments on re-acidification potential of the mine soil. Interestingly, it was found that phosphate and river sediment played quite specific roles in preventing the re-acidification in the mine soil. In addition, the results also indicated that the addition of 25 t ha(-1) lime combined with river sediment (30%) might be an economical method to successfully control the acidification and re-acidification in the extremely acid mine soil, allowing the re-establishment of the plants. Collectively, our results implied that the combined use of NAG test and bioassay assessment was effective in evaluating a reclamation strategy for extremely acidic mine soils. 相似文献
160.
运用概率论和数理统计方法,基于湖南气象观测资料、NCEP资料及地理信息资料,分析了气象因子、地理因子对雨凇天气形成的影响,揭示了各影响因子的临界影响点。进而分析了主要影响因子位于不同影响点时其它因子对雨淞天气形成的作用,在此基础上,研制了基于气象要素因子、地理因子的雨凇日数学模型。选取平均连续雨凇日数、年平均雨凇日数、雨凇最长持续时间等3项与雨凇日数有关的气候指标对模型模拟结果进行了检验,结果表明模型模拟结果与实际观测结果相关性高,均值差异小。雨凇日模型已被用于精细化的雨凇气候区划。 相似文献