森林、茶园和菜园3种土地利用类型下的蝴蝶群落物种与功能多样性比较研究

土地利用变化是蝴蝶多样性丧失的重要原因,为探究森林转变为茶园与菜园后蝴蝶多样性的变化特点,于2019年4—10月采用样线法在江苏宝华山逐月调查了上述3种土地利用类型下的蝴蝶多样性。调查结果显示,共监测到蝴蝶5科47属62种;森林的Shannon Wiener多样性指数、Margalef丰富度指数和Pielou均匀度指数均高于茶园和菜园,但Simpson优势度指数茶园最高;功能丰富度指数（F_ric）、二次熵指数（RaoQ）都是森林显著高于其他2种土地利用类型,但菜园的F_ric显著高于茶园;功能离散度指数（F_div）和功能均匀度指数（F_eve）3种土地利用类型间无显著差异。蝴蝶群落物种和功能多样性与植被类型及其时空变化有明显的相关性,土地利用变化等人类活动对蝶类群落多样性有破坏作用。     

上软下硬地层深基坑结构变形监测及分析*

为探究在上软下硬地层中进行深基坑开挖时围护结构水平位移与内支撑轴力的变化规律,以广州地区某上软下硬地层盾构井深基坑开挖项目为依托,基于现场监测数据进行分析并运用MIDAS/GTS软件开展深基坑开挖全过程的有限元模拟。将围护结构水平位移模拟值与监测值进行对比,验证模型的准确性;改变围护结构嵌固深度、主体结构厚度等工况,研究上述因素对结构水平位移变化产生的影响。研究结果表明:实测围护结构最大水平位移值11.78 mm,位于长边0.7倍基坑深度附近,坑角处位移值最小;改变结构嵌固深度对坑深15 m以下围护结构位移值影响较大,本工程最佳嵌固深度为1.5~3 m;围护结构水平位移会随着结构主体厚度的增加而减小,但最大位移间差值逐渐减小,结构主体厚度设计值宜为0.8~1 m。     

南水北调大型渡槽结构抗震安全性研究

阐述了南水北调中大型渡槽的抗震问题,分别介绍了基于常微分方程求解器(ODE)和有限元方法的大型渡槽动力计算模型、动力特性分析和设置铅芯橡胶支座(LRB)的隔震分析。研究表明,基于ODE求解器的解析和半解析方法有很好的精度和可靠性,可用于大型渡槽的初步设计。结合所得的研究成果,对南水北调的渡槽抗震提出了合理化建议。     

一种新型废旧轮胎组合拦石结构的试验研究

提出了一种由废旧轮胎组成的拦石结构,该结构用钢丝绳将废旧轮胎进行合理的绑扎,使轮胎与轮胎之间紧密连接,然后将该结构绑扎在用废旧钢轨或钢筋混凝土制作而成的柱子上面.当拦石结构受到落石冲击时,利用废旧轮胎的弹塑性变形吸收冲击能量.为了考察这种由废旧轮胎组成的拦石结构的防护效果,设计了试验模型,采用20 kg的砝码模拟落石,...     

Linking trophic positions and flow structure constraints in ecological networks: Energy transfer efficiency or topology effect?

In the present work we investigate whether the distribution of energy flows in ecosystems responds to criteria of trophic organization. We analyzed weighted and unweighted food webs estimating, for each node, trophic position (TP), Shannon's index of inflow diversity (H) and individual contribution to the whole average mutual information (AMI). Finally, we performed the same analysis on simulated webs that were constructed using the following criteria: (a) preserving topology and varying link strength; (b) modifying position of links and their intensities.     

Invasive species impacts on ecosystem structure and function: A comparison of Oneida Lake, New York, USA, before and after zebra mussel invasion

Exotic species invasion is widely considered to affect ecosystem structure and function. Yet, few contemporary approaches can assess the effects of exotic species invasion at such an inclusive level. Our research presents one of the first attempts to examine the effects of an exotic species at the ecosystem level in a quantifiable manner. We used ecological network analysis (ENA) and a social network analysis (SNA) method called cohesion analysis to examine the effect of zebra mussel (Dreissena polymorpha) invasion on the Oneida Lake, New York, USA, food web. We used ENA to quantify ecosystem function through an analysis of food web carbon transfer that explicitly incorporated flow over all food web paths (direct and indirect). The cohesion analysis assessed ecosystem structure through an organization of food web members into subgroups of strongly interacting predators and prey. Our analysis detected effects of zebra mussel invasion throughout the entire Oneida Lake food web, including changes in trophic flow efficiency (i.e., carbon flow among trophic levels) and alterations of food web organization (i.e., paths of carbon flow) and ecosystem activity (i.e., total carbon flow). ENA indicated that zebra mussels altered food web function by shunting carbon from pelagic to benthic pathways, increasing dissipative flow loss, and decreasing ecosystem activity. SNA revealed the strength of zebra mussel perturbation as evidenced by a reorganization of food web subgroup structure, with a decrease in importance of pelagic pathways, a concomitant rise of benthic pathways, and a reorganization of interactions between top predator fish. Together, these analyses allowed for a holistic understanding of the effects of zebra mussel invasion on the Oneida Lake food web.     

松毛虫遗传多样性研究中AFLP反应体系的建立

以油松毛虫为材料,对T4 DNA连接酶不同用量、预扩增中的Mg~(2+)浓度、dNTP浓度、引物浓度以及选择性扩增巾的预扩增产物稀释倍数、Mg2~(2+) 浓度、dNTP浓度、引物浓度和Taq酶浓度进行了比较分析.最终建立了适合松毛虫的AFLP反应体系.用优化的AFLP反应体系,以油松毛虫、赤松毛虫和马尾松毛虫为材料筛选引物,从81对引物组合中筛选出10对多态性高的引物组合.图9参17     

Rarefaction and nonrandom spatial dispersion patterns

Rarefaction estimates how many species are expected in a random sample of individuals from a larger collection and allows meaningful comparisons among collections of different sizes. It assumes random spatial dispersion. However, two common dispersion patterns, within-species clumping and segregation among species, can cause rarefaction to overestimate the species richness of a smaller continuous area. We use field studies and computer simulations to determine (1) how robust rarefaction is to nonrandom spatial dispersion and (2) whether simple measures of spatial autocorrelation can predict the bias in rarefaction estimates. Rarefaction does not estimate species richness accurately for many communities, especially at small sample sizes. Measures of spatial autocorrelation of the more abundant species do not reliably predict amount of bias. Survey sites should be standardized to equal-sized areas before sampling. When sites are of equal area but differ in number of individuals sampled, rarefaction can standardize collections. When communities are sampled from different-sized areas, the mean and confidence intervals of species accumulation curves allow more meaningful comparisons among sites. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.

艾比湖流域不同植物群落土壤呼吸研究

利用开路式土壤碳通量测量系统LI-8100测定艾比湖流域4种植物群落土壤呼吸速率日变化,分析土壤温度、湿度和气温以及空气相对湿度对土壤呼吸速率的影响.结果表明:胡杨、梭梭、芦苇和盐节木4种植物群落的土壤呼吸速率日变化基本呈单峰曲线.胡杨、梭梭和盐节木群落的土壤呼吸速率与地上10 和150 cm处气温均表现为极显著相关.除芦苇群落外,各植物群落土壤呼吸速率与不同深度土壤温度呈极显著负相关.除沙地梭梭群落外,胡杨、盐渍地梭梭、芦苇和盐节木群落的土壤呼吸速率与地上10和150 cm处的空气相对湿度均呈极显著负相关.不同植物群落土壤呼吸速率与土壤湿度呈极显著负相关.多元逐步回归拟合的回归模型均达极显著水平,由土壤温度和湿度共同拟合出的回归模型能够解释土壤呼吸速率变化87%以上的原因.不同植物群落土壤呼吸差异原因的分析显示,细菌、真菌、放线菌以及根系干质量不是造成植物群落土壤呼吸差异的主要原因.      

Influence of Landscape Elements in Riparian Buffers on the Conservation of Semiaquatic Amphibians

Abstract:  Studies on riparian buffers have usually focused on the amount of land needed as habitat for the terrestrial life stages of semiaquatic species. Nevertheless, the landscape surrounding wetlands is also important for other key processes, such as dispersal and the dynamics of metapopulations. Multiple elements that influence these processes should therefore be considered in the delineation of buffers. We analyzed landscape elements (forest cover, density of roads, and hydrographic network) in concentric buffers to evaluate the scale at which they influence stream amphibians in 77 distinct landscapes. To evaluate whether our results could be generalized to other contexts, we determined whether they were consistent across the study areas. Amphibians required buffers of 100–400 m of suitable terrestrial habitat, but interspecific differences in the amount of habitat were large. The presence of amphibians was related to roads and the hydrographic network at larger spatial scales (300–1500 m), which suggests that wider buffers are needed with these elements. This pattern probably arose because these elements influence dispersal and metapopulation persistence, processes that occur at large spatial scales. Furthermore, in some cases, analyses performed on different sets of landscapes provided different results, which suggests caution should be used when conservation recommendations are applied to disparate areas. Establishment of riparian buffers should not be focused only on riparian habitat, but should take a landscape perspective because semiaquatic species use multiple elements for different functions. This approach can be complex because different landscape elements require different spatial extents. Nevertheless, a shift of attention toward the management of different elements at multiple spatial scales is necessary for the long-term persistence of populations.