PHYTOPLANKTON IN THE FOX CHAIN OF LAKES1

ABSTRACT: As part of a comprehensive water quality investigation on the Fox Chain of Lakes during May to October 1975, water samples from the Chain and Cedar Lake (reference) at 25 locations were collected weekly or bi-weekly to determine the species and densities of algae. The results have been evaluated for algal composition, density, and succession for each location. Sixty-four algal species were recovered from 414 samples. The number of species per sampling location varied from 10 at Channel Lake and Lake Marie to 26 on Fox Lake (main) and Grass Lake. Blue green algae were predominant and occurred at 25 of the 25 sampling stations. They consisted mainly of Aphanizomenon flos-aquae. The only flagellate of importance was Ceratium hirundinella, and significant concentrations of this organism were limited to Channel Lake and Lake Catherine. The only green alga bloom was created by Ulothrix variabilis on the waters of Pistakee Lake. Diatoms were quite significant on the shallower water bodies. Algal densities ranged from about 25 to 14,000 cts/ml. The highest count occurred on Mineola Bay. Other high counts (>10,000 cts/ml) observed were waters taken from Channel Lake, Grass Lake, and Fox Lake (main). In Grass Lake, 60 percent of the collections had algal densities in excess of 2,000 cts/ml. Most of these were the diatom Cyclotella meneghiniana.     

蘑菇湖水库的富营养化及水生生态变迁的研究

蘑菇湖水库已处于富营养-重富营养阶段.正在由响应型向非响应型湖泊演变.导致这一结果的原因是多年来石河子市工农业废水和生活污水中所含氮、磷元素超负荷地进入水库,由此引起了水生生态系统的一系列生态变迁和恶性演化.     

Streamwater chemistry and flow dynamics along vegetation-soil gradient in a subalpine Abies fabri forest watershed, China

Streamwater chemistry and spatial flow dynamics from a subalpine Abies fabri forest in an experimental watershed located in the east slope of Gongga Mountain were analyzed to gain insights into the gradient effect of primary community succession on the stream biogeochemical process. Results showed that high sand content (exceeding 80%) and porosity in the soil(exceeding 20% in A horizon and 35% in B horizon), as well as a thick humus layer on the soil surface, made the water exchange quickly in the Huangbengliu (HBL) watershed. Consequently, no surface runoff was observed, and the stream discharge changed rapidly with the daily precipitation. The flow trends of base ions in the stream water were influenced by the Abies fabri succession gradient. Ca^2 , HCO3^- and SO4^2,- were the dominant anions in the streamwater in this region. A significant difference of Ca^2 , HCO3^- and SO4^2- concentration exported between the succession stages in the watershed can be found. But they had the similar temporal change in the stream flow. Ca^2 , HCO3^- and SO4^2- showed significantly negative correlations with the daily precipitation and the stream discharge. Concentrations of Cl^- , Na^ , K^ , and Mg^2 were low in all streamwaters monitored and we observed no differences along the Abies fabri succession gradient. Low ratios of Na. (Na Ca) (range from 0.1 to 0.2) implied cations were from bedrock weathering (internal source process in the soil system) in this region. But, a variance analysis showed there were almost no differences between rainwater and streamwaters for Mg^2 , Na^ , K^ , and Cl^- concentrations. This indicated that they might be come from rainfall inputs(external source). The highly mobile capacity, rapid water exchange between precipitation and discharge, and long-term export lead to this observed pattern were suggested.     

官厅水库浮游植物功能群季节演替及其驱动因子

官厅水库是北京市重要的水源地,其生态环境问题一直深受社会关注。以浮游植物功能群调查为基础,于2010年春夏秋三季对官厅水库进行生态调查,根据水库水环境特征,在永1000、妫1018+1、河口3个不同生境区域设置采样点,进行浮游植物水样采集。共鉴定出浮游植物112种(包括变种),分属于6门52属。浮游植物种类组成:绿藻门23属49种,占种类总数的43.75%;硅藻门12属34种,占30.36%;蓝藻门10属19种,占16.96%;裸藻门4属7种,占6.25%;甲藻门2属2种,占1.79%;隐藻门1属1种,占0.89%。浮游植物丰度秋季(8 889.97×10~4个/L)夏季(7 157.39×10~4个/L)春季(868.97×10~4个/L),三季均值为5 638.78×10~4个/L。3个季节里浮游植物划分为18个功能群,代表性功能群的季节演替为春季(F/MP/H1/C/D/G/W1)→夏季(Tc/M/Wo/C/N/X3/LM)→秋季(Tc/H1/C/D/W1/P)。利用典范对应分析方法,对同步取得的p、TN、TP、WT等环境因子与浮游植物功能群分之间的相关性进行分析。结果显示,WT、p、TP、NH_4-N是官厅水库浮游植物功能群演替的主要驱动因子。     

When Has an Abandoned Field Become a Semi-Natural Grassland or Heathland?

This study presents a meta-analysis of a collective dataset describing the succession from abandoned fields to semi-natural grassland and heathland vegetation over the past century. The study objectives were to develop a method for statistical discrimination between abandoned fields and semi-natural habitats and to analyze the probability that an abandoned field had developed into a semi-natural habitat. A statistical classification model was developed, based on lists of vascular plants from 2059 plots from Danish semi-natural grasslands and heathlands, and abandoned fields of varying age. This model was shown to discriminate effectively between abandoned fields and semi-natural habitats, and it was found to be potentially useful for the detection of abandoned fields approaching semi-natural vegetation. We suggest that the model may help clarify restoration targets and assess biological condition in formerly cultivated areas. Statistical modeling revealed that succession age, period of abandonment and succession trajectory had significant effects on the probability that abandoned fields reached the semi-natural phase. Our study indicates that restoration projects targeting grassland and heathland should take local species pools and soil fertility into account. Nomenclature: Species names follow Flora Europaea (Tutin and others 1964–1993).     

火灾下工程结构连续性倒塌分析与设计方法探讨

给出了火灾下工程结构连续性倒塌的定义,分析了工程结构在火灾作用下的特点,并给出了火灾连续性倒塌判断流程。在介绍目前常用的工程结构抗连续性倒塌分析设计方法的基础上,提出了采用替代路径法中的非线性静力分析方法对建筑结构进行火灾作用下抗连续性倒塌设计的思路。     

Characteristics of Cajander Larch (<Emphasis Type="Italic">Larix cajanderi</Emphasis> Mayr) on Dredging Waste Dumps in the Amur Region

Former dredging sites were studied in the taiga zone of the Amur region (in Khabarovsk Krai). The involvement of Larix cajanderi in plant succession on dredging waste dumps was revealed. Some morphological-anatomical parameters of L. cajanderi needles were compared in trees growing on the dumps and in adjacent open larch stands on waterlogged peaty soils.__________Translated from Ekologiya, No. 4, 2005, pp. 259–263.Original Russian Text Copyright © 2005 by Osipov, Burundukova.     

Vegetation restoration dynamics in the forest-steppe system of the middle Volga region

The current dynamics of ecosystems of the forest-steppe system is most adequately described via determining the probable trajectories of changes in its elements in a simple Markov chain. The obtained data have made it possible to determine the direction of succession and draw its scheme. Theoretically possible series of community development are presented. The succession of community restoration from the spread of shrubs over steppificated fallow lands to the formation of low forests of European bird cherry has been analyzed. The restoration cycle of ecosystem dynamics is described by eight age stages.     

松花江干流2014~2019年夏季着生藻类群落结构特征及其对环境因子的响应

着生藻类的群落特征常被用作评价水生态环境质量的重要指标.通过对2014~2019年夏季松花江干流着生藻类的群落结构特征及其对环境因子的响应关系分析,对松花江干流的水生态环境质量状况及变化趋势进行探讨.结果表明,2014~2019年夏季松花江干流共鉴定着生藻类4门和58属.其中硅藻门28属、绿藻门17属,蓝藻门10属和裸藻门3属.流域主要组成物种为硅藻门、绿藻门和蓝藻门,分别占总数48.28%、29.31%和17.24%.着生藻类细胞密度平均值为4.35×10⁴ ind·cm^-3,变化范围在1.29×10⁴~8.42×10⁴ ind·cm^-3之间,优势属主要为硅藻门小环藻属（Cyclotella）、直链藻属（Melosira）、星杆藻属（Asterionella）、桥弯藻属（Cymbella）、针杆藻属（Synedra）、羽纹藻属（Pinnularia）、舟形藻属（Navicula）和绿藻门的栅藻属（Scenedesmus）等.分析松花江干流水环境质量演变趋势,溶解氧含量逐年升高,氨氮、总磷和总氮含量呈先升高后下降趋势,2019年水体改善效果显著.运用冗余分析（RDA）探究着生藻类与环境因子间的变化关系,发现驱动松花江干流着生藻类群落结构演替的主要环境因子随时间推移而有所变化,溶解氧、氨氮、总氮、总磷和生化需氧量等指标是这一区域着生藻类种类分布的重要环境影响因子.     

水质改善的浮游植物群落演替机制模拟研究

模拟了广州市某河流的不同水质改善阶段,并研究其对铜绿微囊藻（Microcystis aeruginosa）、斜生栅藻（Scenedesmus obliquus）、短线脆杆藻（Fragilaria brevistriata）和易变裸藻（Euglena mutabilis）生长及超氧化物歧化酶（SOD）活性的影响.同时,考察了由4种藻类构成的人工群落的生长特征和群落演替率,以探讨河流水质改善过程中浮游植物群落演替机制.结果表明：4种藻类对氮、磷营养盐和COD_Cr等胁迫的响应程度差异及种间相互竞争作用等是水质改善过程中导致浮游植物群落演替的影响因素;水质改善初期（1~3 d）,群落演替率与改善程度呈显著的正相关关系（p<0.05）;但较长时间（约13 d）处于相对稳定的环境条件下时,群落演替速率将趋于零,从而达到一个新的稳定状态.水质的不断改善将导致浮游植物的种类和数量呈现出蓝藻和裸藻逐渐减少,而绿藻和硅藻逐渐增多的变化趋势.