Chironomid pupal exuviae and larvae of two storage reservoirs in The Netherlands

For three years chironomid larvae were collected bimonthly with a grab sampler in two deep storage reservoirs in The Netherlands. Chironomid pupal exuviae were collected monthly, from April to November, with a handnet. Net samples yielded more taxa than grab samples. The taxa found in net samples originated from more habitats, than taxa found in grab samples. The relative contribution of Orthocladiinae was much larger in net samples. Based on the results obtained in the two reservoirs, some advantages and disadvantages of both sampling methods are discussed.     

The spring development of phytoplankton in Lake Erken: species composition,biomass, primary production and nutrient conditions — a review

Relative abundance and within-lake distributions of three fishes, northern redbelly dace (Phoxinus eos), finescale dace (Phoxinus neogaeus), and central mudminnow (Umbra limi), were examined using minnow traps in Tuesday Lake, a small bog lake in the Upper Peninsula, Michigan. For these species, catches in minnow traps placed at the perimeter of the lake were 21 to 52 times higher than catches in midlake traps. Variance: mean ratios of perimeter trap catches indicated that both dace species were highly aggregated while the distribution of mudminnows was less aggregated or random. Over an 11 day period during which all fish caught were removed from the lake, catch per unit effort (CPUE) of both dace species declined in response to fish removal. In contrast, CPUE for mudminnows was low initially, increased to an asymptote and then declined only in the last 5 days of the fish removal. The patterns of CPUE for mudminnows indicated that mudminnow trapability and/or activity was reduced in the presence of high densities of dace. The low abundance of dace in traps with many mudminnows suggested mudminnows avoided traps already containing dace. Throughout the removal period, CPUE provided an accurate index of dace abundance, whereas this was true for mudmnnows only after dace populations had been reduced drastically. Therefore, in any use of minnow traps to estimate populations, both spatial distributions and relative species abundance of small fishes must be taken into account.     

Ecological studies of spores of aquatic hyphomycetes in the cringle brook,lincs

The aquatic Hyphomycete spora of the Cringle Brook, Lincs, was examined by foam sampling and by the use of cellophane impaction traps between August, 1968 and January, 1970.The species most frequently found (Tetracladium marchalianum, Alatospora acuminata and Flagellospora curvula) were generally in agreement with those found by other workers in temperate areas. Impaction trap samples generally contained fewer species than foam samples but filiform spore types such as Flagellospora were more frequently found on traps than in foam suggesting that impaction is more selective towards the filiform spore type than is foam. Many species increased in frequency in autumn accompanying and following leaf fall, and the winter spora was dominated by Alatospora acuminata, Clavariopsis aquatica, Clavatospora stellata, Flagellospora curvula and Lemonniera aquatica. During the summer the spora was dominated by Tetracladium marchalianum.The role of foam and impaction in the balance of aquatic spore populations is discussed in relation to techniques available for their study.     

2002-2016年华北平原植被生长状况及水文要素时空特征分析

基于MODIS增强型植被指数（EVI）资料,结合降水、GRACE重力卫星水储量（TWS）、地下水、土壤水等资料,分析华北平原植被2002-2016年间的生长状况及各水文要素时空分布特征。研究结果表明：（1）2002-2016年间华北平原植被呈好转趋势,降水、水储量、土壤水、地下水等水文要素值呈减少趋势。（2）黄淮平原区植被以农作物为主,植被覆盖度呈增加趋势,而降水、水储量、地下水、土壤水均呈减少趋势,超采地下水灌溉农作物是短期内保障粮食安全的重要措施。（3）燕山-太行山山麓平原区、冀鲁豫低洼平原区的城乡居民用地区域植被覆盖显著减少,而降水增多,水储量、土壤水、地下水减少,人类活动对植被和水文要素贡献量大。（4）山东丘陵农林区分布着林地和草地,这些区域生长季的植被指数呈减少趋势,与降水量减少呈正相关关系。在气候变化和人类活动影响的大背景下,探讨不同生态环境的植被生长特征,清楚植被对水文变化的响应机理,可以消除影响植被生长的不利因素,为制定合理用水制度提供理论依据。     

盐增强培养对弗氏链霉菌产新霉素的影响

目的:弗氏链霉菌(Streptomyces fradiae)作为氨基糖苷类抗生素新霉素的主要生产菌株,其新霉素B具有抗菌活性强、抗癌、抗HIV等作用,提高新霉素B的效价具有重要意义.方法:在满足微生物正常生长所需盐离子的条件下,通过盐增强培养的方式向培养基中添加不同种类、浓度无机盐来改变细胞壁附近的理化特性、渗透压以及...     

鼎湖山植物群落α多样性与环境的关系

用样带取样法,来研究不同取样尺度和不同取样尺度条件下的多个环境因子与鼎湖山植物群落α多样性的关系.取样尺度分别为10、20、40、80m和160m.涵盖鼎湖山主要的植被类型：季风常绿阔叶林、针阔混交林、沟谷常绿阔叶林和针叶林.相关分析和主成分分析结果表明,环境因子对各层次的α多样性的影响程度各不相同,达到显著相关性的取样尺度也不一样,表现出较大的复杂性,同时也表明样带上的环境异质性较高.因此,用海拔梯度作为主要的环境梯度来研究鼎湖山植物群落多样性具有合理性.海拔高度与乔木层多样性的关系在所有取样尺度上都较密切,这说明海拔高度可能是影响乔木层α多样性的最重要环境因子.     

基于湿度分布特征的小尺度土壤碳通量空间采样策略

由于土壤碳通量的空间异质性很强,传统的随机抽样方法无法对区域土壤碳通量进行准确估算,而多点采样需耗费大量的人力及设备成本,因此确定适当的采样点数量及分布策略对于区域土壤碳通量的测算非常重要。提出一种基于湿度空间分布特征的小尺度土壤碳通量空间采样策略:首先利用无线传感网密集测量区域的土壤湿度,根据湿度数据的空间分布特征划分监测区域,通过Hammond Mc Cullagh方程计算各子区域内的最优采样点数量,最终确定整个监测区域的空间采样点部署策略。提出的方法考虑了各子区域间土壤碳通量空间分布的差异,使得采样点的部署位置与土壤碳通量的分布具有较好的相关性。研究结果证明:土壤碳通量部署策略能够获得比均匀部署策略、随机部署策略更高的区域土壤碳通量估算准确度。     

油藏微生物群落研究的方法学

油藏微生物群落的解析和认知是开发和应用微生物采油技术的基础。利用各种提高油藏微生物可培养性的方法和非培养技术解析不同油藏微生物的群落结构、功能和多样性,对定向调控油藏微生物群落、开发和应用有效微生物驱油技术具有重要的指导意义。通过调查新近发展的提高微生物可培养性的方法和措施以及不依赖于培养的分子微生物生态学技术,总结了油藏微生物群落研究方法学的最新进展。提高微生物可培养性的方法和措施主要通过模拟微生物的生存环境,减少富营养的毒害作用、添加信号分子维持微生物细胞间的作用和提供新型电子供体和受体等手段采用稀释法、高通量培养法等方法得以实现;不依赖于培养的分子微生物生态学技术主要包括荧光原位杂交、末端限制性片断长度多态性分析、变性梯度凝胶电泳和构建克隆文库等技术。这些方法学的进展为更有效的获得各种油藏微生物资源、调控油藏微生物群落以提高石油采收率提供理论指导。     

Airborne pollen in Padua (NE-Italy): A comparison between two pollen samplers

During recent years a gradual decrease inallergenic airborne pollen concentration hasbeen observed in the monitoring station ofPadua (Italy). Because technical checks of thesampler were not able to explain this trend,the results obtained from two twinpollen-samplers (Lanzoni VPPS 2000), placed twometres apart, were compared.An eight-week sampling was carried out duringthe year 2000 from July to September.Subsequent analysis revealed no statisticallysignificant difference between the dataobtained with the two instruments. On the otherhand, both samplers captured high levels offungal spores. We conclude that the observednegative trend in pollen count is real and notrelated to technical biases.