Epidemiologic Analysis of Factors Associated with Local Disappearances of Native Ranid Frogs in Arizona

Abstract:  We examined factors that may independently or synergistically contribute to amphibian population declines. We used epidemiologic case–control methodology to sample and analyze a large database developed and maintained by the Arizona Game and Fish Department that describes historical and currently known ranid frog localities in Arizona, U.S.A. Sites with historical documentation of target ranid species ( n = 324) were evaluated to identify locations where frogs had disappeared during the study period (case sites) and locations where frog populations persisted (control sites). Between 1986 and 2003, 117 (36%) of the 324 sites became case sites, of which 105 were used in the analyses. An equal number of control sites were sampled to control for the effects of time. Risk factors, or predictor variables, were defined from environmental data summarized during site surveys and geographic information system data layers. We evaluated risk factors with univariate and multifactorial logistic-regression analyses to derive odds ratios (OR). Odds for local population disappearance were significantly related to 4 factors in the multifactorial model. Disappearance of frog populations increased with increasing elevation (OR = 2.7 for every 500 m, p < 0.01). Sites where disappearances occurred were 4.3 times more likely to have other nearby sites that also experienced disappearances (OR = 4.3, p < 0.01), whereas the odds of disappearance were 6.7 times less (OR = 0.15, p < 0.01) when there was a source population nearby. Sites with disappearances were 2.6 times more likely to have introduced crayfish than were control sites (OR = 2.6, p = 0.04). The identification of factors associated with frog disappearances increases understanding of declines occurring in natural populations and aids in conservation efforts to reestablish and protect native ranids by identifying and prioritizing implicated threats.     

常减压蒸馏装置改造危险因素分析及安全对策

应用危险性预分析法,对一套常减压蒸馏装置扩容改造施工的危险因素进行分析,制定出相应的防范对策,以确保改造工作的安全.     

建设农村小康社会与发展生态农业

论述生态农业在建设农村小康社会中的重要作用，分析生态农业面临的形势和问题，并提出政策建议。     

"绿色会计"理论初探

由于自然资源的掠夺性开发和以牺牲环境为代价赚取经济利益最大化的现象还不同程度存在,使扣除经济活动中投入的环境成本后的国民生产总值--绿色GDP得到普遍关注.绿色会计是为保护生态环境而研究生态环境成本和价值、提供生态环境变化信息的环境会计,已越来越受到人们关注.文章就绿色会计概念、目标、主体、客体、科目设置及信息披露作为重点,进行了初步探讨.     

含半无限长裂纹压电材料的Ⅲ型强度因子

研究了含半无限长裂纹压电材料在平面内电场和反平面荷载作用下的问题 ,得到了满足拉普拉斯方程、裂纹面边界条件的位移函数解和电势函数解及电弹场的基本解 ,并得到了应力、应变、电位移强度因子和能量释放率。研究结果表明 ,在裂尖 ,电场强度没有奇异性 ,而应变、应力、电位移具有奇异性。     

岷江上游半干旱河谷土壤成土特征研究：以大沟流域为例

岷江上游半干旱河谷位于新构造运动活动带，其土壤形成和发育过程有着鲜明的区域特征。本文结合该区域的自然地理特点，综合分析各成土因素和土壤性状，对该区域土壤的成土特征进行了深入的分析和研究。     

循环流化床锅炉脱硫的影响因素分析

较为系统的分析了影响循环流化床锅炉脱硫的各因素,其中包括运行床温、Ca与S物质的量、床料粒度、流化速度、以及SO_2在炉膛停留时间等,提出在不同运行条件下利用拟合曲线找出最佳脱硫工况。     

毛乌素沙地樟子松人工林根内真菌群落结构与功能时间动态特征

为揭示毛乌素沙地樟子松人工林根内真菌群落结构和功能时间动态特征,以毛乌素沙地不同林龄（23、33和44 a）樟子松人工林为研究对象,采用高通量测序技术,比较分析不同月份（4~9月）樟子松人工林根内真菌群落组成及其对环境因子的响应. 结果表明：①樟子松根内真菌群落分布存在明显的季节性,月份对樟子松根内真菌多样性指数影响显著（P<0.05）,在5月和7月较高;樟子松根内真菌多样性指数随林龄的增大而逐渐减小,林龄对其的影响不显著. ②毛乌素沙地樟子松根内真菌优势菌门为子囊菌门（Ascomycota）;不同营养型真菌相对丰度随月份变化,优势类群为腐生-共生营养型真菌、未定义腐生菌和外生菌根真菌;5月、7月和9月的指示外生菌根真菌分别为囊蘑属（Melanoleuca）、缘腺革菌属（Amphinema）和口蘑属（Tricholoma）. ③毛乌素沙地樟子松根内真菌群落分布受年均相对湿度、年均降水量、土壤孔隙度、土壤铵态氮、年均日照时数、年均温和土壤含水量的显著影响（P<0.05）,指示菌种主要受土壤有机碳含量、孔隙度、年均降水量和年均空气湿度的影响. 气候和土壤性质等环境因子的变化塑造了毛乌素沙地樟子松人工林根内真菌群落结构和功能的时间动态特征,而林龄的贡献较小. 研究结果可为樟子松人工林可持续经营管理提供理论依据.     

Abiotic control on the dissipation of chlorpyrifos spiked in an Udic Ferrisol at a lower dosage

The dissipation routes of chlorpyrifos spiked in an Udic Ferrisol at the dosage of 400 ng g^?1, which represents a residual level after an agricultural application, were studied in a laboratory, using the natural soil under three moisture regimes, sterilised, and organic matter-free soils in the dark at 20°C. The obtained results showed that higher soil moisture caused faster dissipation, and the abiotic and biotic contributions to the total dissipated amount of the applied chlorpyrifos in the soil accounted for 77.3–85.2% and 14.7–22.7%, respectively. In the sterilised soil, the contribution of organic matter to chlorpyrifos dissipation was noticed to account for 95% in the earlier two weeks, and was nearly equal to that of soil minerals two weeks after the incubation.     

短程硝化—厌氧氨氧化组合工艺在脱氮领域的研究进展

基于全程硝化反硝化的传统生物脱氮工艺在硝化过程中需要大量氧气供应,反硝化过程需要有机物作为碳源,存在能耗与药耗过大的问题.为了降低废水脱氮的成本,短程硝化(PN)—厌氧氨氧化(ANAMMOX)组合工艺(PNA工艺)得到了高速发展.综述了PNA工艺的影响因素,重点介绍了4种基于PN与ANAMMOX原理开发的衍生PNA工艺...