Measuring the complexity of interaction webs using vertical links between functional groups

Ecological insights into the usually high complexity of interaction webs demand a simplification of their structure to concentrate on the most important interactions within a community. One way to achieve this goal is to use functional groups (FGs). Using simple and partial Mantel tests the vertical interactions between FGs from different trophic levels were studied both at a disturbed grassland site and at a similar but undisturbed site. The resulting interaction structures of both ecosystems were compared. (i) An approximately 50% higher vertical FG-connectance could be found in the undisturbed than in the disturbed grassland; (ii) a much higher percentage of significant correlations did exist between FGs in the undisturbed than in the disturbed system; and (iii) the disturbed grassland was characterized by more simply structured biotic interaction patterns. From these results it was concluded that (a) Mantel tests are a useful tool for detecting significant interaction patterns (web links) between FGs, and that (b) FG-connectance is a powerful measure of complexity and functional diversity of communities.     

Verifying an Extinction Debt among Lichens and Fungi in Northern Swedish Boreal Forests

Abstract:  Destruction and fragmentation of natural habitats results in small species populations that face increased risk of extinction. A time delay may be involved in the regional extinction of species, and the number of species that eventually may go extinct in the future is called the "extinction debt." In boreal Sweden, we examined whether the number of epiphytic crustose lichens and wood-inhabiting fungi in old-growth forest remnants diverges from species richness levels in forest patches that have been naturally isolated for millennia. An excess of species in forest remnants could indicate the presence of an extinction debt. Observed species richness in 32 old-growth forest remnants (also called woodland key habitats [WKHs]) was compared with predicted species richness. To predict species richness we used regression models based on data from 46 isolated old-growth forest patches in a forest-wetland matrix. The reference landscape is ancient and assumed to reflect the conditions of insular floras in dynamic equilibrium. Stand factors constituted predictive variables in the models. The observed number of lichen species was higher than expected (i.e., an extinction debt among lichens may exist). By contrast, there was no significant difference between observed and expected species richness among wood-inhabiting fungi. The species richness of wood-inhabiting fungi has adjusted to the changes in forest and landscape structure more rapidly than the species richness of lichens. Differences in substrate dynamics between epiphytes on living trees and species growing on decaying logs might explain the difference between species groups. The results also indicate that population densities of red-listed species were low, which may result in continuing extinctions of red-listed species. The importance of WKHs might be overvalued because species may be lost if conservation efforts consider only protection and preservation of WKHs.     

地幔流体基本特征及成因

与构造环境密切相关的氧逸度是控制地幔流体成分的最根本因素CO2和H2O为大多数地幔流体的主要成分。俯冲板块的脱水脱气作用、地幔原始残留挥发份及地幔部分熔融作用是地幔流体的主要来源。     

A comparison of numerical solutions of partial differential equations with probabilistic and possibilistic parameters for the quantification of uncertainty in subsurface solute transport

Traditionally, uncertainty in parameters are represented as probabilistic distributions and incorporated into groundwater flow and contaminant transport models. With the advent of newer uncertainty theories, it is now understood that stochastic methods cannot properly represent non random uncertainties. In the groundwater flow and contaminant transport equations, uncertainty in some parameters may be random, whereas those of others may be non random. The objective of this paper is to develop a fuzzy-stochastic partial differential equation (FSPDE) model to simulate conditions where both random and non random uncertainties are involved in groundwater flow and solute transport. Three potential solution techniques namely, (a) transforming a probability distribution to a possibility distribution (Method I) then a FSPDE becomes a fuzzy partial differential equation (FPDE), (b) transforming a possibility distribution to a probability distribution (Method II) and then a FSPDE becomes a stochastic partial differential equation (SPDE), and (c) the combination of Monte Carlo methods and FPDE solution techniques (Method III) are proposed and compared. The effects of these three methods on the predictive results are investigated by using two case studies. The results show that the predictions obtained from Method II is a specific case of that got from Method I. When an exact probabilistic result is needed, Method II is suggested. As the loss or gain of information during a probability–possibility (or vice versa) transformation cannot be quantified, their influences on the predictive results is not known. Thus, Method III should probably be preferred for risk assessments.     

生态足迹动态预测模型构建与分析

生态足迹的动态预测能够为区域可持续发展政策的制定提供科学的理论依据，但其研究仍处于探索阶段。以武汉市为例，选取表征社会经济发展的重要指标建立了社会经济系统指标体系，在对武汉市1978~2004年生态足迹时间序列计量的基础上，应用偏最小二乘算法构建了生态足迹动态预测模型，并根据〖WTBX〗VIP〖WTBZ〗值的大小分析了各指标对生态足迹的影响机制。结果表明，武汉市“十一五”规划期间生态足迹呈上升趋势，其中规划期末2010年的人均生态足迹为2810 5 hm2，高于全球生态阈值（人均生态足迹为2200 0 hm2）；根据〖WTBX〗VIP〖WTBZ〗值得出人口、能源消费量和第三产业所占比重为最重要的影响因子，并就如何实现武汉市“十一五”规划目标提出了政策性建议。将科技进步贡献率、能源消费量等重要因子纳入社会经济系统指标体系，弥补了在生态足迹定量测度中忽略社会、经济、科技因素对其影响的不足；另一方面，引入偏最小二乘算法中的〖WTBX〗VIP〖WTBZ〗值更准确地评价了各指标对生态足迹变化的影响，为生态足迹动态预测研究作了进一步地完善与改进。〖     

酚类化合物对硝化颗粒污泥活性抑制的定量结构-活性相关研究

测定了酚类化合物对硝化颗粒污泥活性抑制的logIC50值,以量子化学参数为自变量,应用偏最小二乘法（PLS）,建立了酚类化合物对硝化颗粒污泥活性抑制的定量结构-活性相关（QSAR）模型。模型所提取的PLS主成分所能解释的因变量总方差的比例Qc2um为0.820,表明模型具有较好的稳定性和预测能力。模型的结果表明,影响酚类化合物对硝化颗粒污泥活性抑制的主要因素是logkow、CCR和Ehomo,酚类化合物对硝化颗粒污泥活性抑制的logIC50随着分子logkow的增大而减小,随着Ehomo和CCR的增大而增大。     

高氢分压下厌氧颗粒污泥演变过程研究

为了探究厌氧颗粒污泥用于氢辅助原位生物法沼气提纯的可行性，在高氢分压ASBR中对厌氧颗粒污泥演变过程进行了考察，包括反应器性能和厌氧颗粒污泥特性变化情况.结果表明，在进水COD负荷低于5g/（L·d）时，氢辅助原位生物法沼气提纯中高氢分压、高进水COD负荷和高剪切力新环境促使厌氧颗粒污泥向小粒径方向演变，系统运行性能良好、高效，此时厌氧颗粒污泥可以通过营造具有极低氢分压的微环境强化基于HIT（种间氢传递）途径丙酸降解；但随着进水COD负荷进一步提高，超过6g/（L·d）时，系统出现不可控的丙酸积累.因此，需要寻求其他技术手段来缓解更高进水COD负荷条件下氢辅助原位生物法沼气提纯系统中丙酸积累问题.     

多输入多输出系统的相干性的问题分析

从相干性的来源入手,依次介绍了常相干性、偏相干性、重相干性的物理意义和运算关系,并研究了在实际试验中对相干性的估计和误差方面的问题。此外,还列出了一些对相关性理解和利用方面的一些命题,并依次进行了论证。