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61.
Donglin Wang Jie Zhou Hui Lin Junwen Chen Jing Qi Yaohui Bai Jiuhui Qu 《Frontiers of Environmental Science & Engineering》2023,17(3):34
62.
Facilitation, or positive plant–plant interaction, has received increasing concern from ecologists over the last two decades. Facilitation may occur through direct mitigation of severe environments or indirect mediation by a third participant from the same or different trophic levels. The copper(Cu) tolerant species Elsholtzia splendens facilitates the establishment and growth of co-occurring Commelina communis through indirect enrichment of microbial activity. However, whether and how E. splendens impacts the microbial community that is associated with C. communis is less known. We characterized the soil bacterial community in the rhizosphere of C. communis in the absence and presence of E.splendens using PCR-DGGE(polymerase chain reaction-denaturing gradient gel electrophoresis) and sequencing. The result showed that the richness of the bacterial community increased, but diversity and evenness remained similar, in the presence of E. splendens.Chloroflexi, Acidobacteria and Proteobacteria were the most dominant bacteria. The relative abundance of dominant and minor bacterial groups showed distinctly different responses to E. splendens. Principal component analysis and redundancy analysis indicated that variation of the bacterial community was determined by multiple factors and might be driven by the tested soil parameters collectively, or alternatively changed through plant root exudates or other microorganisms. Our results enhance the understanding of how the bacterial community associated with a beneficiary plant responds to a benefactor plant and suggests that the changes of bacterial community composition may have far-reaching influence on plant–soil feedback and the aboveground plant community in the long run. 相似文献
63.
The effect of mine tailings and sewage sludge was evaluated on sorption, desorption, availability and distribution of copper in two soils, one high (sandy soil) and one low in copper (clay soil). In both soils contaminated by mine tailings the copper sorption capacity and the affinity of the substrate for the metal decreased substantially compared to the uncontaminated soils, however, the sorption remained always high in the clay soil substrates. In the substrates with sandy soil, the high Cu content and lower clay content were determining factors in the lower magnitude of the sorption. Similarly, metal desorption was closely related to these two parameters, and it was higher in clay soil with lower pH. In general, the application of sewage sludge favored the sorption of Cu in soils contaminated and uncontaminated with mine tailings, and in all cases desorption decreased, an effect that remained for at least 30 days. Simple extraction of Cu with CaCl2 and diethylenetriaminepentaacetic acid gave contradictory results, so a careful choice of the procedure is required, depending on the level of metal in the soil and on the acting principle of the extracting agent. In that relation, more complete information on the changes in the metal forms was obtained by application of the sequential extraction procedure proposed by the European Community Bureau of Reference. 相似文献
64.
65.
In this paper we show that plants respond to downstream ambient water quality after controlling for permitted levels of pollution. We find if past water quality declines by one percent, plants reduce current pollution by 0.35 percent. The magnitude of this coefficient is comparable to the coefficient on permitted discharge levels i.e. regulatory stringency itself. Results are consistent with two mechanisms. First, a decline in water quality may lead to more stringent permits that would raise the cost of abatement of a plant significantly. Second, the plant is likely to be subject to increased public pressure in response to poor water quality. Indeed, as expected, the impact of water quality becomes stronger in locations with higher median household income, higher percent carpooling to work, or lower percent of manufacturing employment but surprisingly with lower median age of residents, lower percent with bachelor׳s degree or higher percent of families with children. 相似文献
66.
Mining generates risk of environmental and social harm for Indigenous peoples but can also generate substantial revenues for them, creating opportunities for community development in a context where economic and social disadvantage is the norm. Especially as mining revenues should, in part, compensate for mining’s negative social and environmental impacts, it is vital that mineral taxation on Indigenous lands reflect a careful assessment of appropriate tax mechanisms and a matching of these with community priorities. Yet little has been written that could serve as a guide for Indigenous decision makers. This article contributes to an understanding of the issues and choices facing Indigenous communities in designing mineral taxation regimes, by focusing on the question of economic risk. Risk arises as a key variable in choosing or designing a mineral taxation regime in three ways. Different approaches to mineral taxation are inherently more or less risky, in the sense that they are more or less certain to generate tax revenues. A second aspect of risk involves the degree of economic certainty or predictability associated with different types of commodities and projects. Third, the risk tolerance of Indigenous peoples and communities can vary significantly. We show how Indigenous groups can integrate and address these different dimensions of risk, by recognising the ‘risk consequences’ associated with different approaches to mineral taxation and choosing an approach that reflects, as fully as possible, the group’s risk tolerance. 相似文献
67.
以典型的亚热带大型山地丘陵湖泊——江西省仙女湖研究为例,2014~2015年每月对仙女湖湖区及主要入湖河流进行了大型底栖动物群落的周年动态研究。经鉴定得底栖动物111种,隶属3门53科77属。其中软体动物40种,节肢动物61种,环节动物10种。优势种为中华颤蚓、梨形环棱螺、河蚬、锯齿新米虾、羽摇蚊、粗腹摇蚊属、前突摇蚊属、霍甫水丝蚓。仙女湖大型底栖动物年平息栖息密度为346 ind./m2,年平均生物量为54.26 g/m2;不同区域和季节底栖动物的栖息密度与生物量有显著差异(P0.05),河流型生境R2年平均栖息密度最大,为722 ind./m2。湖泊型生境L4年平均栖息密度最小,为251 ind./m2。1月的平均栖息密度最高,为567 ind./m2,5月平均栖息密度最低,为163 ind./m2。用辛普森多样性指数对不同区域水质进行评价,结果表明,入湖河流和钤阳湖为轻度污染,舞龙湖为中度污染。系统聚类和MDS排序分析表明,大型底栖动物的分布具有环境空间异质性,可以划分为2个群落。 相似文献
68.
Cajo J. F. Ter Braak Herbert Hoijtink Wies Akkermans Piet F. M. Verdonschot 《Ecological modelling》2003,160(3):235
To predict macrofaunal community composition from environmental data a two-step approach is often followed: (1) the water samples are clustered into groups on the basis of the macrofauna data and (2) the groups are related to the environmental data, e.g. by discriminant analysis. For the cluster analysis in step 1 many hard, seemingly arbitrary choices have to be made that nevertheless influence the solution (similarity measure, clustering strategy, number of clusters). The stability of the solution is often of concern, e.g. in clustering by the
program. In the discriminant analysis of step 2 it can occur that a water sample is misclassified on the basis of the environmental data but on further inspection happens to be a borderline case in the cluster analysis. One would then rather reclassify such a sample and iterate the two steps. Bayesian latent class analysis is a flexible, extendable model-based cluster analysis approach that recently has gained popularity in the statistical literature and that has the potential to address these problems. It allows the macrofauna and environmental data to be modelled and analyzed in a single integrated analysis. An exciting extension is to incorporate in the analysis prior information on the habitat preferences of the macrofauna taxa such as is available in lists of indicator values. The output of the analysis is not a hard assignment of water samples to clusters but a probabilistic (fuzzy) assignment. The number of clusters is determined on the basis of the Bayes factor. A standard feature of the Bayesian method is to make predictions and to assess their uncertainty. We applied this approach to a data set consisting of 70 water samples, 484 macrofauna taxa and four environmental variables for which previously a five cluster solution had been proposed. The standard for Bayesian estimation, the Gibbs sampler, worked fine on a subset with only 12 selected taxa but did not converge on the full set with 484 taxa. This is due to many configurations in which the assignment probabilities are all very close to either 0 or 1. This convergence problem is comparable with the local optima problem in classical cluster optimization algorithms, including the EM algorithm used in Latent Gold, a Windows program for latent class analysis. The convergence problem needs to be solved before the benefits of Bayesian latent class analysis can come to fruition in this application. We discuss possible solutions. 相似文献
69.
Malan Yi Yao Fang Guoping Hu Shufeng Liu Jinren Ni Tang Liu 《Frontiers of Environmental Science & Engineering》2022,16(6):79
70.
基于2018年1—11月骆马湖水质和底栖动物逐月监测数据,利用Goodnight指数(GBI)、生物学污染指数(BPI)、Shannon-Wiener指数(H′)等生物学指数对水质现状进行了评价。结果表明,骆马湖ρ(总氮)年均值为2.31 mg/L,ρ(总氮)和ρ(溶解氧)呈先下降后上升趋势;ρ(总磷)年均值为0.05 mg/L,先上升于8月达到峰值(0.15 mg/L)后下降;高锰酸盐指数呈先上升后下降趋势;ρ(氟离子)呈逐渐下降趋势,水温和电导率存在明显季节变化,pH值呈逐渐升高趋势。共鉴定出底栖动物27种,其中软体动物5种,环节动物7种,节肢动物15种。铜锈环棱螺(Bellamya aeruginosa)、红裸须摇蚊(Propsilocerus akamusi)、纹沼螺(Parafossarulus striatulus)、苏氏尾鳃蚓(Branchiura sowerbyi)、霍甫水丝蚓(Limnodrilus hoffmeisteri)、多巴小摇蚊(Microchironomus tabarui)和中国长足摇蚊(Tanypus chinensis)是现阶段优势种。全湖底栖动物年均密度为174.5个/m 2,年均生物量为24.93 g/m 2,表现出明显的时空差异。水质评价结果表明,骆马湖水环境处于中污染状态。结合近年来研究结果,骆马湖底质荒漠化现象趋于好转,但富营养化趋势正在加深。 相似文献