The paleolimnology of North Pond: watershed-lake interactions

We examined the stratigraphic record of North Pond, a small, oligotrophic lake in western Massachusetts, U.S.A. to describe late and post-glacial watershed-lake interactions. In particular we investigated the effects of two similar vegetation changes in the watershed on lake biogeochemistry. There was a transient (about 100 years) decline in hemlock ca. 7500 yr B.P. that has not been recorded in other pollen stratigraphies in the northeast. The second event was the classical hemlock decline that occurred ca. 4800 yr B.P. and lasted about 2000 years. This decline occurred throughout the range of hemlock and is thought to have been caused by a pathogen. As the climate began to warm ca. 10 000 yr B.P., a spruce dominated boreal woodland was established in the watershed. Sediment chemistry data showed that as soils became more acidic, the lake also acidified as evidenced by diatom-inferred (DI) pH. Hemlock was established in the watershed by about 8000 yr B.P. This was accompanied by a slight decrease in DI pH. The transient hemlock decline ca. 7500 yr B.P. was associated with an increase in sedimentary charcoal particles, that suggested fire was responsible for its demise. The diatom stratigraphy indicated a brief, slight, increase in productivity and alkalinity and a brief decrease in lakewater dissolved organic carbon concentrations. Aquatic microfossil data indicated a decrease in the area of the littoral zone ca. 7500 yr B.P. Following the transient decline the lake became more acidic. There were only brief, subtle changes associated with the classical hemlock decline, including a slight decline in DI pH. Although the two disturbances involved a similar vegetation shift, the timing and mechanisms of the disturbances had a greater impact on lake biogeochemistry.     

Periphyton communities in Amazonian black- and whitewater habitats: Community structure, biomass and productivity

Chlorophyll a-concentrations, AFWD (ash-free-dry-weight) and photosynthesis rates were estimated for periphyton assemblages in Amazonian black-and white-water habitats over 14 months. Cellulose-acetate strips were incubated in situ and showed few major differences in periphyton quality as compared to natural substrata. The only exceptions were submersed Igapó forest leaves, which exhibited higher proportions of green algae and cyanobacteria though not producing differences in total periphyton biomass. Enclosure experiments showed a considerable nutrient release by inundated non-senescent Igapó forest leaves. Periphyton biomass and productivity were found to be highest in black-and white water mixing zones, where biomass peaked at 41.6 mg Chla/m² and 19.8 g/m² AFDW. Production was estimated to be 380 gC/m²·a. Maximum biomass of periphyton in floating meadows was 46 mg Chla/m² and 10.6 g/m² AFDW, with an annual production of 170 gC/m²·a. Solimões main channel periphyton values were low: maximum Chla was 7.1 mg/m², AFDW 0.8 g/m² and annual production was estimated to be 30 gC/m². Blackwater periphyton values were lower compared to whitewater and mixed water values but an enlarged trophogenic zone has to be taken into account. Highest Chla content reached 30.9 mg/m², AFDW 1.43 g/m². Estimated annual production was 110 gC/m². Observed mean periphyton productivity of Amazonian blackwater habitats approximately corresponded to mesotrophic attached algae productivity in temperate zones, whereas productivity of whitewater periphyton approached those of temperate eutrophic lakes. The role of periphyton in the Amazon food web is discussed.     

Disaster Management and Community Planning, and Public Participation: How to Achieve Sustainable Hazard Mitigation

The paper offers first a brief historical overview of disaster management planning. Second, it reviews Australian and American research findings and show that they urge the field of disaster management to shift its focus from response and recovery to sustainable hazard mitigation. It is argued that in order for this shift to occur, it is necessary to integrate disaster management and community planning. Current practice seldom reflects such a synthesis, and this is one of the reasons why hazard awareness is absent from local decision-making processes. Third, it is asserted that if mitigative strategies are to be successfully implemented, then the disaster management process must incorporate public participation at the local decision-making level. The paper concludes with a case study of California's Portola Valley, which demonstrates that when public participation is integrated into disaster management planning and community planning, the result is sustainable hazard mitigation.     

旅游地衰退与复苏的驱动力分析--以几个典型旅游景区为例

旅游发展到现阶段，部分旅游地面临着衰退的威胁。有些旅游地走向衰退后，外界所做的一些努力未能使它们走向复苏，如七星岩、岳阳楼；有些旅游地走向衰退后，经过外界努力，它们却走向了复苏，如丹霞山、鼎湖山。通过对这些案例的分析与比较研究，运用形象本底分析等方法，得出市场潜在需求是旅游地衰退与复苏的根本驱动力的结论，并在此基础上提出了指导旅游开发的几点建议。     

化石群落与层序地层的耦合关系研究——以塔里木盆地西部中新生代有孔虫群落与层序地层关系研究为例

本文研究的是大陆边缘海以底栖有孔虫为主的化石群落与层序地层的关系。海平面变化是控制化石群落演替和识别划分层序的主要因素。化石群落在一个完整海水进退旋回中呈机会种群落、平衡种群落、终极种群落演替变化,在化石丰度、多样度、均衡度、成壳类型等方面分异显著,与层序地层的三级层序的海进体系域、凝缩期沉积、高位体系域具有密切的耦合关系。化石群落的演替变化是对海洋环境变迁的能动反映。因此,化石群落的研究可以帮助识别和优化层序、沉积体系域和层序界面,从而为层序地层的准确识别划分提供新的思路。     

四平市合理开发利用水资源的重要意义

四平市由于没有合理开发利用地下水资源，从而导致了区域性的地下水位下降。同时水质遭受污染，生态环境失去平衡，由此给四平市造成了巨大的经济损失,文章最后从多方面，不同角度论述了合理开发利用地下水的有效措施及其重要意义。     

Research on Ecostratigraphy of Changhsingian at Meishan Section D, Changxing, Zhejiang Province

On the basis of researches over several years on biostratigraphy of Changhsingian at Meishan Section D in Changxing County, the abundant materials were accumulated. This paper studies the escostratigraphy and establishes 7 community zones (CZ), in ascending order, Sinoplatysomus-Gernitzina-Clarkina subcarinata, Tapashanites-Nodosaria-Clarkina subcarinata,Crurithyris-Geinitzina-Clarkina subcarinata,Glomospira-Clarkina changxingensis, Colaniella-Clarkina changxingensis,Rotodiscoceras-Palaeofusulina-Hindeodus typicalis,Clarkina meishanensis-Hypophiceras.The habitat type (HT) is diffent from upper shallow sea to the lower part of the lower shallow sea.     

皇甫川流域百里香草原和人工沙棘灌木林的水分利用特征

使用LI-6400光合系统测定仪、LI-3000A叶面积仪等，对皇甫川流域百里香草原和中国沙棘灌木林的优势植物进行了光合速率、蒸腾速率测定，同时还测定了植物水分、土壤水分及群落地上生物量。根据所测数据计算得到了这两个群落优势植物光合和蒸腾的日变化特点、光合水分利用效率，分析了两个群落优势植物叶片含水量、自然饱和亏及水势等植物生理水特征。通过群落优势植物种群的蒸腾失水和土壤水分的分析，探讨了由于土地利用方式的不同，产生的这两个群落生态水的一些明显差异。     

黑河甘肃段浮游植物群落结构演变趋势

为探究西北干旱区内陆河流域水生态系统时空演变规律,2017年7月对黑河甘肃段进行了浮游植物的采样调查,并收集1981、1997、2008年浮游植物夏季调查数据,分析黑河上中下游浮游植物物种、生物多样性和优势种等群落结构的演变特征,同时提出生物活动力指标以表征河流生物的活动能力和活跃程度。结果表明：在空间分布上,黑河中游在各年份都具有最为丰富稳定的浮游植物群落结构,物种数（61属）、生物多样性指数（2.87）和生物活动力指数（0.194万cells·hm^-2）均高于上下游。在时间尺度上,上游浮游植物群落变得持续丰富;中游从1981年持续衰落到2008年后出现反转并快速恢复到2017年更为丰富和活跃的水平;下游则呈现出持续衰落的态势。以1981年为基准,黑河中游水域面积到2010年减小5.2%,浮游植物生物活动力降低了16.5%,到2017年水域面积增加1.2%,浮游植物生物活动力增加了4.3%。黑河浮游植物对流域天然湿地及水域的变化具有强烈的敏感性和依赖性,浮游植物演变特征与湿地水域面积变化趋势一致。     

西藏雅鲁藏布江流域典型沙漠区生态修复植物群落物种多样性

为了深入了解和探讨西藏沙化土地治理区的植物群落的结构类型、组织水平和稳定程度,根据西藏雅鲁藏布江河谷沙地山南市全国防沙治沙综合示范区20个样地的调查资料,分析了西藏山南市全国防沙治沙综合示范区植物群落物种多样性特征。结果表明：西藏山南市全国防沙治沙综合示范区的植物有34种,藏沙蒿（Artemisia wellbyi）、花棒（Hedysarum scoparium）、桑（Morus alba）、沙打旺（Astragalus adsurgens）和沙蒿（Artemisia desertorum）占优势地位。综合示范区固沙植被平均盖度为31.6%±13.1%;平均生长高度为41.2±19.9 cm;平均生长密度为4.6±4.7株·m^-2。植物群落物种多样性H指数平均为0.99±0.54;物种多样性D指数平均为2.55±1.37;物种均匀度平均为1.76±0.75。