Predicted warming and browning affect timing and magnitude of plankton phenological events in lakes: a mesocosm study

1. Aquatic ecosystems in Northern Europe are expected to face increases in temperature and water colour (TB) in future. While effects of these factors have been studied separately, it is unknown whether and how a combination of them might affect phenological events and trophic interactions. 2. In a mesocosm study, we combined both factors to create conditions expected to arise during the coming century. We focused on quantifying effects on timing and magnitude of plankton spring phenological events and identifying possible mismatches between resources (phytoplankton) and consumers (zooplankton). 3. We found that the increases in TB had important effects on timing and abundance of different plankton groups. While increased temperature led to an earlier peak in phytoplankton and zooplankton and a change in the relative timing of different zooplankton groups, increased water colour reduced chlorophyll‐a concentrations. 4. Increased TB together benefitted cladocerans and calanoid copepods and led to stronger top‐down control of algae by zooplankton. There was no sign of a mismatch between primary producers and grazers as reported from other studies. 5. Our results point towards an earlier onset of plankton spring growth in shallow lakes in future with a stronger top‐down control of phytoplankton by zooplankton grazers.     

干旱对东北春玉米生长发育和产量的影响

选取玉米品种丹玉39为供试材料,利用大型农田水分控制试验场,采用大田池栽方式,在玉米三叶-拔节期、拔节-吐丝期、吐丝-乳熟期分别开展中度干旱胁迫及复水控制对比试验,分析3个关键生育时期干旱胁迫对春玉米生长发育和产量的影响.结果表明：与水分适宜对照（CK）相比,三叶-拔节期遭受干旱胁迫后,全生育期推迟13 d,至拔节普遍期,株高偏低29.8%,叶面积偏小41.2%,复水后,株高和产量得到较大程度恢复,果穗性状和最终产量差异不大;拔节-吐丝期遭受干旱胁迫后,全生育期缩短7 d,至吐丝普遍期,株高偏低18.6%,叶面积偏小14.1%,果穗长、穗粒数、果穗干质量、穗粒质量分别下降6.9%、19.1%、28.1%和29.4%,空秆率增加13.3%;吐丝-乳熟期遭受干旱胁迫后,全生育期缩短15 d,生长至乳熟普遍期,株高偏低2.3%,叶面积偏小37.3%,果穗长、穗粒数、果穗干质量、穗粒质量分别下降9.2%、24.1%、30.8%和27.9%,空秆率增加24.5%.拔节-吐丝期、吐丝-乳熟期干旱胁迫处理并复水后,玉米株高恢复不明显,产量降幅显著.     

Nitrification in terrestrial hot springs of Iceland and Kamchatka

Archaea have been detected recently as a major and often dominant component of the microbial communities performing ammonia oxidation in terrestrial and marine environments. In a molecular survey of archaeal ammonia monooxygenase (AMO) genes in terrestrial hot springs of Iceland and Kamchatka, the amoA gene encoding the alpha-subunit of AMO was detected in a total of 14 hot springs out of the 22 investigated. Most of these amoA-positive hot springs had temperatures between 82 and 97 degrees C and pH range between 2.5 and 7. In phylogenetic analyses, these amoA genes formed three independent lineages within the known sequence clusters of marine or soil origin. Furthermore, in situ gross nitrification rates in Icelandic hot springs were estimated by the pool dilution technique directly on site. At temperatures above 80 degrees C, between 56 and 159 mumol NO(3)(-) L(-1) mud per day was produced. Furthermore, addition of ammonium to the hot spring samples before incubation yielded a more than twofold higher potential nitrification rate, indicating that the process was limited by ammonia supply. Our data provide evidence for an active role of archaea in nitrification of hot springs in a wide range of pH values and at a high temperature.     

Earlywood vessel size of oak as a potential proxy for spring precipitation in mesic sites

Aim In this study, we evaluate the importance of the mean earlywood vessel size of oaks as a potential proxy for climate in mesic areas. Location The study was conducted in Switzerland at three forest sites dominated by oak (Quercus petraea and Q. pubescens). The three sites were in different climatic zones, varying mainly in terms of precipitation regime. Methods Three 50‐year‐long site chronologies of mean earlywood vessel size and tree‐ring widths were obtained at each site and related to monthly meteorological records in order to identify the main variables controlling growth. The responses of mean vessel size to climate were compared with those of the width variables to evaluate the potential climatic information recorded by the earlywood vessels. Results The results show that the mean vessel size has a different and stronger response to climate than ring‐width variables, although its common signal and year‐to‐year variability are lower. This response is better in particular at mesic sites, where it is linked to precipitation during spring, i.e. at the time of vessel formation, and is probably related to the occurrence of only a few processes controlling vessel growth, whereas radial increment is controlled by multiple and varying factors. Main conclusions The mean earlywood vessel size of oak appears to be a promising proxy for future climate reconstructions of mesic sites, where radial growth is not controlled by a single limiting factor.     

Plankton composition and water quality in a pond of spring origin in Turkey

Phyto/zooplankton composition, chlorophyll a, and some water quality parameters were investigated in a spring-originated pond in Central Anatolia between February 2001 and January 2002. Water temperature, pH, dissolved oxygen, Secchi depth, total and calcium hardness, nitrate-nitrogen, nitrite-nitrogen, ammonia-nitrogen, total phosphorus, and soluble reactive phosphorus levels were analyzed. A total of 49 species belonging to Bacillariophyceae, Chlorophyceae, Cyanophyceae, Cryptophyceae, and Dinophyceae were identified. The highest phytoplankton abundance was found in August, whereas the lowest was determined in January. Phytoplankton abundance increased from February to August and declined in the following months. The Bacillariophyceae were dominant in the phytoplankton community. A total of 21 species of Rotifera, 2 species of Cladocera, and 1 genus of Copepoda were found. The zooplankton community was dominated by Rotifera. The highest abundance of zooplankton was recorded in July and the lowest value in November. The annual mean concentration of chlorophyll a was measured as 1.90 μg l⁻¹. In spite of these eutrophic levels (mean values of total phosphorus and nitrate-nitrogen: 0.069 mg P l⁻¹ and 0.68 mg N l⁻¹), phytoplankton cannot grow satisfactorily because of the short water retention time (0.6 day⁻¹). The shallowness of the pond together with the low phytoplankton biomass and the high concentrations of nutrients are discussed.     

土壤水分对温室春黄瓜苗期生长与生理特性的影响

以津优1号黄瓜为试验材料．研究了土壤不同水分含量对温室春黄瓜苗期生长与生理特性的影响。结果表明,在土壤水分为田间持水量90％时．黄瓜幼苗长势健壮,茎粗大,根系活力强,叶绿素含量和光合速率高．与其它处理差异显著,说明土壤含水量过高或过低均不利于培育黄瓜壮苗。株高和叶面积随土壤含水量的升高而增加;细胞汁液浓度随土壤含水量的升高而降低．且对植株水分状况反应十分敏感,可以用来作为判断植株水分盈亏状况的生理指标。     

春季高寒山区牧草低温保护物质变化与其脱冻适应间关系研究

为了了解牧草低温保护物质与其抗冷冻的关系,在高寒山区测定了几种多年生牧草根中低温保护物质的含量和几种蔗糖酶活力的变化。结果表明,在4月土壤解冻期间,无芒雀麦、花雀麦、垂穗披碱草和草地早熟禾根中的蔗糖含量分别下降了74．1％、66．2％、45．2％和69．6％,果糖含量分别下降了72．0％、38．0％、68．3％和84．6％,葡萄糖含量分别下降了66．7％、62．5％、42．2％和65．2％,脯氨酸含量分别下降了83．0％、51．0％、43．3％和70．6％,可溶性蛋白质变化不大;蔗糖合成酶、蔗糖磷酸合成酶活性下降,蔗糖分解酶活性增加,蔗糖分解酶活性是蔗糖合成酶活性的22～35倍,是蔗糖磷酸合成酶活性的55～80倍。研究结果说明,春季牧草萌发时,根中已糖含量的下降是蔗糖分解酶活性增加的结果,根中脯氨酸作为氮的贮藏物质被用于根的呼吸和蛋白质合成。春季牧草根的抗寒能力随着根中低温保护物质的减少而下降,这也说明牧草的低温保护物质和牧草的抗寒性密切相关。     

小麦低分子量麦谷蛋白亚基与面团流变学特性关系的研究

采用十二烷基硫酸钠-聚丙稀酰胺凝胶电泳(SDS-PAGE)分离方法,以牛血清蛋白(67kD)和卵清蛋白(43kD)为分子量标记,对甘肃河西灌区近几年选育的17个小麦品系以及大面积栽培的2个春小麦品种的低分子量麦谷蛋白亚基组成以及不同亚基对面团流变学特性(面团韧性P、延伸性L、面团筋力W)的影响进行分析。19个试验材料中共标记出从35．2～60．5kD的LMW-GS共32条谱带;通过单因素方差分析(ANOVA)和逐步回归分析确定出对面团流变学特性P、L、W值影响显著的7个LMW-GS,分子量由高到低为：52．7kD、52kD、49．3kD、46．7kD、44．8kD、44．2kD、35．2kD。其中35．2kD和46．7kD亚基能显著地增加面团P值,44．8kD亚基能显著地降低面团P值;44．2kD和49．3kD亚基显著增加面团L值,52．7kD亚基降低面团L值;44．8kD、52．7kD亚基能显著降低面团的W值,52．0kD和46．7kD亚基能显著提高面团W值。     

广东金山温泉沉积物中原核与真核微生物多样性初步分析

[目的]本研究旨在采用不同的PCR引物对广东省恩平市金山温泉的高温水底沉积物微生物多样性进行初步的分析.[方法]采用改进的玻璃珠法抽提温泉沉积物中环境基因组DNA,通过对用4对引物分别扩增得到的原核微生物16S rRNA基因和真核微生物ITS序列的分析,将所得到的数据与国际基因数据库GenBank进行相似性比较并构建系统发育树.[结果]研究发现原核类群G的 14个优势克隆中7个都属于蛭弧菌属(Bdellovibrio).与它们最相似的序列是从海洋中分离到的两个菌株 Bacteriovorax sp. NE1 (EF092445)和Bdellovibrio sp. JS5 (AF084859),相似性分别为96%和99%.原核类群X的4个序列主要属于蓝细菌类群,其中JS-X2与在美国黄石公园温泉发现的Uncultured Cyanobacterium (L35331)有95%的相似性,并且与已经全基因组测序的嗜热蓝细菌聚球藻Thermosynechococcus elongatus BP-1 (47118315)有89%的相似性.真核类群Z有三个类群,分别是Penicillium sp.,Lodderomyces sp.和Gloeotinia sp..其中大部分序列与青霉属相似性在88%～ 90%之间.[结论]所得到的结果显示金山温泉中的微生物多样性十分丰富.