Growth and antioxidant system of the cyanobacterium Synechococcus elongatus in response to microcystin-RR

Microcystins, one type of the cyanobacterial toxins, show a broad range of hazardous effects on other organisms. Most of the researches on the toxic effects of microcystins have involved in animals and higher plants. Little work, however, has been done on evaluating the mechanisms of microcystin toxicity on algae. In this study, the toxicological effects of microcystin-RR (MC-RR) on the cyanobacterium Synechococcus elongatus were investigated. For this purpose, six physio-biochemical parameters (cell optical density, reactive oxygen species (ROS), malondialdehyde (MDA), glutathione (GSH), glutathione peroxidase (GSH-Px) and glutathione S-transferase (GST)) were tested in algal cells when exposed to 100 mug(-1) microcystin-RR. The results showed that the growth of Synechococcus elongatus ( expressed as optical density) was significantly inhibited compared with the control. At the same time, the treated algae exhibited a pronounced increase in production of ROS and MDA after 6 days exposure to microcystin-RR. Signi. cant changes in GSH levels and GSH-Px, GSH activities were also detected in algal cells, with higher values being observed in the toxin treated algae after 6 days exposure. GST activities in the treated algae exhibited a decline after exposure and rapid augmentation on day 3, thereafter, they kept at a high level when compared to the control group. GSH contents and GSH-Px activities were also significantly raised in the toxin-treated algae cells from day 3, but they showed a sharp decrease on day 4, which was the onward of cell proliferation. These results suggested that oxidative stress manifested by elevated ROS levels and MDA contents might be responsible for the toxicity of microcystin to Synechococcus elongatus and the algal cells could improve their antioxidant ability through the enhancement of enzymatic and non-enzymatic preventive substances.

Physiological and biochemical microcystin-RR toxicity to the Synechococcus elongatus

Freshwater Microcystis may form dense blooms in eutrophic lakes. It is known to produce a family of related cyclic hepatopeptides (microcystins, MC) that constitute a threat to aquatic ecosystems. Most toxicological studies of microcystins have focused on aquatic animals and plants, with few examining the possible effects of microcystins on phytoplankton. In this study we chose the unicellular Synechococcus elongatus (one of the most studied and geographically most widely distributed cyanobacteria in the picoplankton) as the test material and investigated the biological parameters: growth, pigment (chlorophyll-a, phycocyanin), photosynthetic activity, nitrate reductase activity, and protein and carbohydrate content. The results revealed that microcystin-RR concentrations above 100 mug (.) L-1 significantly inhibited the growth of Synechococcus elongatus. In addition, a change in color of the toxin-treated algae (chlorosis) was observed in the experiments. Furthermore, MC-RR markedly inhibited the synthesis of the pigments chlorophyll-a and phycocyanin. A drastic reduction in photochemical efficiency of PSII (F-v/F-m) was found after a 96-h incubation. Changes in protein and carbohydrate concentrations and in nitrate reductase activity also were observed during the exposure period. This study aimed to evaluate the mechanisms of microcystin toxicity on a cyanobacterium, according to the physiological and biochemical responses of Synechococcus elongatus to different doses of microcystin-RR. The ecological role of microcystins as an allelopathic substance also is discussed in the article. (C) 2004 Wiley Periodicals, Inc.

放牧强度对江河源区垂穗披碱草（Elymus natans）／星星草（Puccinellia tenuflora）混播草地群落和高原鼠兔（Ochotona curzoniae）的影响

在江河源区披碱草（Elymus natans）／星星草（Puccinellia tenuflora）混播人工草地上进行了两个放牧季（2003年6月29日～9月20日和2004年6月29日～9月20日）的牦牛放牧试验，研究了放牧强度对混播草地群落特征和高原鼠兔（Ochotona curzoniae）种群密度的影响。结果表明：在两个放牧季内，随着放牧强度的提高，草地群落的盖度、地上现存量和优势种植物（披碱草和星星草）的株高降低，且放牧强度与其呈极显著负相关关系；对照处理组群落的物种多样性指数、丰富度指数和均匀度指数最低，中度放牧组最高，该结果支持“中度干扰理论”。随着放牧强度的提高，高原鼠兔的种群密度增加，且放牧强度与其呈极显著的正相关关系；不同放牧强度下群落的物种多样性指数、丰富度指数和均匀度指数与高原鼠兔的种群密度之间存在着一定的相关关系。

小麦族多年生植物的染色体组，系统学与进化

禾本科Poaceae小麦族Triticeae Dumort.的多年生物种是该族的重要组成部分，约占该族植物总数的三分之二以上，广泛地分布于全世界各地，主要集中于北半球温带地区。由于小麦族多年生植物的种类繁多，生态环境多样、种间和种内的形态变异极大，而大多数多年生物种又具有多倍体起源，加之属间及种间的天然杂交也十分频繁，以致于造成了其系统学研究的巨大困难。通过近三十年来对小麦族植物的大量属间和种间杂交以及对其杂种的减数分裂染色体配对行为分析，对该族各个属的染色体组构成及其在进化上的关系和意义已经有了较为深入的认识。小麦族中的多倍体属是由来源不同的二倍体祖先属经过天然杂交和染色体自然加倍而形成，因而研究和分析各个二倍体属之间及与多倍体属间的染色体组亲缘关系，为揭示小麦族各属、种之间的系统与进化关系提供了非常有价值的资料。本研究通过对一些小麦族多年生植物的形态学、地理分布、属间和种间杂交以及染色体组之间的亲缘关系的一系列研究，对不同属以及同一属内不同组的物种之间的进化关系进行了深入的分析，并对其系统学进行了讨论。同时对于一些异常的细胞遗传学现象，如染色体在属间杂种的缺失、重复以及染色体配对的遗传控制也作了初步的分析。通过上述研究，本研究对于小麦族多年生的一些属、特别是披碱草属Elymus厶、拟鹅观草属Pseudorocgneria Love和大麦披碱草属Hordelymus (Jessen) Harz,的染色体组构成以及与各物种的形态学关系，物种之间的进化关系均有了更为深刻的认识。

羊草遗传多样性分析和赖草属的分子系统发育

羊草（Leymus chinensis（Trin.）Tzvel.或Aneurolepidium chinense Trin.），隶属禾本科（Gramineae），大麦族（Hordeae），小麦亚族（Triticieae），赖草属（Leymus），兼具重要的生态价值和经济价值。面向国家重大需求，本论文选择羊草作为主要研究对象，开展了两方面的研究工作，即我国羊草种质资源的遗传多样性评价和赖草属物种的系统发育分析。 羊草是一种多年生根茎型禾草，根据叶色可以划分为黄绿型和灰绿型两种生态型。其分布范围横穿亚欧草原的东部，包括朝鲜和蒙古的西部，以及西伯利亚的西北部，集中分布于我国的东北部。羊草是我国典型草原植物群落中的优势种。它可以在多种土壤和气候条件下正常生长，如松嫩平原、内蒙古草原和黄土高原。从另一个角度讲，不同类型的生境也造就了羊草丰富的遗传多样性。 自上世纪90年代中期开始，我们陆续从我国东北部6个省市收集了293份羊草种质，包括205份灰绿型羊草和88份黄绿型羊草。经过连续3年的观测记录，通过37个重要农艺性状，对293份羊草的遗传多样性进行了评估。依据10个质量性状和27个数量性状，统计了羊草不同性状和不同地域羊草的Shannon遗传多样性指数，同时还使用了主成分分析和通径分析做了相关统计。结果显示：（1）与黄绿型羊草相比，灰绿型羊草具有更高的遗传变异（P<0.05）。结合这两个趋异型羊草的分布范围，可以得出两种类型羊草之间存在稳定的遗传差异;（2）通径分析显示，羊草营养生长性状和遗传多样性两者的组合效应可以解释羊草生殖特性中20.6％的遗传变异;（3）在124-128ºE这一区域，羊草的遗传多样性指数最高（H＝2.252），表明这一地区具有最丰富的羊草种质资源。 赖草属（Leymus Hochst.）是一个异源多倍体属，约有34个物种，该属未知基因组的起源一直争论不休。其倍性范围从四倍体（2n=4x=28）、八倍体（2n=8x=56）一直到十二倍体（2n=12x=84）。新麦草属（Psathyrostachys Nevski）只含有Ns一个基因组，约有9个物种。这两个属都是多年生牧草，具有抗旱、抗病和耐盐碱等生物学特性。 应用核糖体ITS（Internal Transcribed Spacer）序列和叶绿体trnL-F序列，我们对13个赖草属物种、小麦族18个属（40份二倍体材料）、以及Elymus californicus和Bromus catharticus，共计57份材料进行了系统发生分析。ITS序列分析表明，赖草属分别与新麦草属和小麦族中一个未知属在进化上具有紧密的关系。ITS谱系树表明赖草属内部存在大量的分化，以及赖草属物种具有多次起源的特征。trnL-F序列分析表明，赖草属物种的母本，部分来自Ns基因组，部分来自Xm基因组，这可能与赖草属物种的地理分布有关，分布于亚欧大陆的物种其母本是新麦草属，而分布于北美的大部分物种其母本是Xm基因组。trnL-F序列分析还表明，E. californicus和赖草属未知的基因组具有紧密的关系。以上研究结果表明：（1）从分子层面证明，赖草属的未知基因组并非来自薄冰草属，或是一个修正的新麦草基因组，其基因组组成应是NsNsXmXm;（2）赖草属物种的母本，部分来自Ns基因组，部分来自Xm基因组，这可能与赖草属物种的地理分布有关;（3）E. californicus的母本是Xm基因组，父本是Ns基因组，该物种应从披碱草属转移至赖草属。

云南盘ju属Discogobio鱼类四新种

报道云南盘ju属鱼类4新种: 多鳞盘juD. polylepis、长鳔盘juD. macrophysallidos、长体盘juD. elongatus和短鳔盘juD. brachyphysallidos。全模标本存中国科学院昆明动物研究所。图4参9

铬离子对藻类生长的影响

利用自然光照条件,在不同铬离子质量浓度下,对5种藻类的生长进行了实验研究。研究结果表明:5种藻类在不同的光波长下,其吸收光谱存在两个最强的吸收区:420～440nm的蓝紫光部分和660nm的红光部分;在不同铬离子质量浓度0～20.63mg·L-1范围内,5种藻类生长受到不同程度的抑制,其耐受性也尽不相同,经过分析和比较后得出5种藻类对铬的耐受性大小顺序为:微囊藻(Microcystis)>水华鱼腥藻(Anabaena flos-aquae)>细长聚球藻(Synechococcus elongatus)>斜

Sequences of cytochrome b gene for primitive cyprinid fishes in East Asia and their phylogenetic concerning

1140 bp of cytochrome b gene were amplified and sequenced from 14 species of primitive cyprinid fishes in East Asia. Aligned with other ten cytochrome b gene sequences of cyprinid fish from Europe and North America retrieved from Gene bank, we obtained a matrix of 24 DNA sequences. A cladogram was generated by the method of Maximum likelihood for the primitive cyprinid fishes. The result indicated that subfamily Leuciscinae and Danioninae do not form a monophyletic group. In the subfamily Danioninae, Opsariichthys biden and Zacco platypus are very primitive and form a natural group and located at the root. But the genera in subfamily Danioninae are included in different groups and have not direct relationship. Among them, Aphyocypris chinensis and Yaoshanicus arcus form a monophyletic group. Tanichthys albonubes and Gobiocypris rarus have a close relation to Gobioninae. The genus Danio is far from other genera in Danioninae, In our cladogram, the genera in Leuciscinae were divided into two groups that have no direct relationship. The genera in Leuciscinae distributed in Europe, Sibera and North America, including Leuciscus, Rutilus, Phoxinus, N. crysole, Opsopoeodus emilae, form a monophyletic group. And the Leuciscinae in southern China including Ctenopharyngodon idellus, Mylopharyngodon piceus, Squalibarbus and Ochetobius elongatus have a common origination.

中国横断山区裂腹鱼亚科(Schizothoracinae)部分类群的系统分类和谱系地理学研究

论文以线粒体细胞色素b 基因对裂腹鱼属鱼类的两个分布广泛的物种 (灰裂腹鱼Schizothorax griseus 和光唇裂腹鱼Schizothorax lissolabiatus)进行了谱系地理学研究；对灰裂腹鱼进行了物种分化研究；对光唇裂腹鱼进行了地理变异研究；并进一步对横断山区分布的裂腹鱼属鱼类进行了谱系地理学研究；整理了中国境内伊洛瓦底江水系分布的裂腹鱼属鱼类。对灰裂腹鱼和光唇裂腹鱼的谱系地理学研究结果表明：1、来自不同水系的灰裂腹鱼和光唇裂腹鱼个体间存在明显的遗传差异，两个物种各自不呈单系；灰裂腹鱼和光唇裂腹鱼同域分布的个体有共享单倍型的情况；北盘江、牛栏江、乌江和元江的个体在系统树上有较近的亲缘关系。2、对灰裂腹鱼进行了重新描述并对来自于不同水系被认为是灰裂腹鱼的标本进行了查看，结果表明：灰裂腹鱼分布于金沙江下游及其支流；分布于澜沧江的，过去被认为是灰裂腹鱼的种类代表裂腹鱼属鱼类一新种——裸腹裂腹鱼Schizothorax nudiventris sp. nov.；分布于南盘江的过去被认为是灰裂腹鱼的种类代表一新种——异鳔裂腹鱼Schizothorax heterophysallidos sp. nov.；分布于北盘江的过去被认为是灰裂腹鱼的种类代表一新种——北盘裂腹鱼Schizothorax beipanensis sp. nov.。3、本研究还陈述了光唇裂腹鱼的各地理种群(怒江、澜沧江、元江、南盘江和北盘江)部分形态特征以及差异情况。主成分分析结果表明：怒江和澜沧江个体在形态上无差异；澜沧江上游和下游个体在部分特征上表现出一定程度上的渐变异。4、横断山区裂腹鱼属鱼类的谱系地理学研究表明：系统树不支持裂腹鱼属鱼类亚属的划分；本属不同种类Cyt b 基因序列的最大遗传距离为11.2%；怒江和澜沧江的个体以较高的支持率聚成一单系；伊洛瓦底江水系与雅鲁藏布江的个体以较高的支持率聚成一单系；金沙江流域与元江、南盘江、北盘江的个体聚成一单系；晚中新世(9.5 Ma) 和早上新世(3.6 Ma)的青藏高原的强烈隆升可能是横断山区裂腹鱼属鱼类物种分化的重要时间；裂腹鱼属鱼类的演化是历史生物地理学过程中隔离分化假说的一个实例；横断山区的古河道向南入海可能有3 个方向，它们是雅鲁藏布-伊洛瓦底江方向、怒江-澜沧江方向、金沙江及其支流-红河方向(包括南盘江-红河)；不支持长江第一湾为袭夺湾的观点，古金沙江入古红河可能不经剑川-洱海一线；滇中、滇东北水系发育复杂。5、本研究还对中国境内伊洛瓦底江水系分布的裂腹鱼属鱼类进行了整理。认为本地区裂腹鱼属鱼类共8 种(包括2 新种)：南方裂腹鱼Schizothorax meridionalis、奇异裂腹鱼Schizothorax heteri sp. nov.、独龙裂腹鱼Schizothorax dulongensis、软刺裂腹鱼Schizothorax malacathus、少鳞裂腹鱼 Schizothorax oligolepis、吸口裂腹鱼Schizothorax myzostomus、细身裂腹鱼 Schizothorax elongatus 和白体裂腹鱼Schizothorax leukus sp. nov.。

云南抚仙湖的鱼类及其在进化过程中的生物学表达

本文依据生物与环境相统一、生物的演化必然在其生态学特性上表达出来，从进化的观点出发，以生态学作为一种手段，结合湖泊的地质变迁，借以阐明抚仙湖的鱼类区系在漫长的演化过程中是怎样形成的。全文分八部分。着重介绍区系的概貌、起源及鱼类演化的生物学表达。经鉴定，抚仙湖共有土著鱼类23种，根据属的分布中心可把它们分为四个分布型，即广泛分布型、云南弧分布型、南亚分布型和青藏高原分布型。它们从宏观上反映了抚仙湖鱼类区系起源的背景和演化的阶段性。研究结果表明，抚仙湖鱼类的演化是从时间(time)、空间(space)、形式(form)三个方面展开的。具体表现在鱼类物种和区系两个层次的生物学特点均源自对抚仙湖由浅变深的时、空演变过程的适应。随着湖泊由浅变深和贫营养化，抚仙湖的鱼类区系产生了一系列相应的变化：鱼类区系的空间分布由古抚仙湖的广泛性浅水生活类型分化为目前的沿岸浅水区生活类型、敞水区中上层生活类型、深水区中下层生活类型；种间食性出现多种多样的分歧；生长的演化表现为生长速度减慢，体型趋向细长；繁殖期延长，而且每两个产卵批次之间有一定的时间间隔，个体的繁殖力趋向降低，种群性比趋向悬殊，雌性增多。这些综合分化的结果就形成了今天抚仙湖鱼类的多样性。它们各得其所，各就其位，保持一个相对稳定而复杂的网络关系。文中还记述了2新种和1新亚种，它们是抚仙高原鳅(Triplophysa fuxianensis)、后鳍云南鳅(Yunnanilus opisthopterus)和小鳔长身 (Acheilognathus elongatus elongatus)。这进一步反映了云南高原湖泊鱼类区域化较突出的特点。抚仙湖鱼类区是云南高原湖泊鱼类区系的典型代，而且是云南众多湖泊中唯一仍基本保持其自然而貌的湖泊，因此，发展抚仙湖渔业生产的方针应不同于其它湖泊，即有选择地增殖土著鱼类，首先是增殖鱇 白鱼和云南倒刺鲃；谨慎引入外来种。同时还要兼顾湖泊的多功能性加以综合利用，不可就某一功能就满打满算。

中国急流牙甲族的系统学研究

急流牙甲族Sperchopsini属于鞘翅目Coleoptera牙甲科Hydrophilidae的水牙甲亚科Hydrophilinae，共包括五属，即水龟虫属 Hydrocassis、革牙甲属 Ametor、Sperchopsis、Anticura、Cylomissus，世界共计有25种，我国分布有2属18个种。 本文回顾了水甲虫、牙甲科以及急流牙甲族的研究简史；综述了水甲虫在分类学、保护生物学、形态学、遗传学、分子生物学等方面研究进展，总结了水甲虫与生态因子的关系以及水甲虫作为生态系统健康指示物的可行性。还简要介绍了昆虫分子系统学，以及细胞色素氧化酶亚基I（COI）和rDNA内部转录间隔区（ITS）在昆虫学研究中的应用。 通过对收集到的700余号急流牙甲族的标本观察和分类研究，发现了一新种（内蒙水龟甲Hydrocassis mongolica sp.nov.）。并且对已知全部种类重新作了描述，特别是长茎革牙甲 Ametor elongatus雄性外生殖器部分，首次对7个种类（长茎革牙甲 Ametor elongatus、粗革牙甲 Ametor scabrosus、帝水龟甲 Hydrocassis imperialis、伪舟水龟甲Hydrocassis pesudoscapha、条纹水龟甲Hydrocassis scapulata、舟水龟甲 Hydrocassi scapha、四川水龟甲Hydrocassis sichuana）的雌性个体进行了描述。编制了急流牙甲族的分属、分种检索表。 采用支序分类学的方法对中国急流牙甲族种类的系统发育关系进行探讨。结果显示革牙甲属内的A. latus、A. rudesculptus、A. rugosus 及A. scabrosus 构成单系（不包括A. elongates），支持皱革牙甲A. rugosus和A. latus属于革牙甲属。水龟虫属内H. anhuiensis、H. baoshanensis、H. lacustris、H. pseudoscapha、H. scaphoides、H. scapulata、H. sichuana、H. taiwana、H. uncinata、H. schillhammeri构成一个单系。水龟虫属包括两大类群，一类群包括H. anhuiensis、H. lacustris、H. scapulata、H. sichuana 、H. taiwana，另一类群包括H. baoshanensis、H. scaphoides、 H. schillhammeri 、H. uncinata。两类群的不同之处在于后一类群的阳基侧突上有一齿状凸起。 测序了H. scapulata、H. sichuana和H. mongolica雌雄各一个个体的COI和ITS2序列。全部的COI基因序列为828bp，编码275个氨基酸。H. scapulata的ITS2序列有446bp，H. sichuana的有456bp，H. mongolica的有455bp。用MEGA 3.1计算比对距离（pairwise distances）和构建邻近系统树。结果显示对于COI，种内的比对距离分别是0(H. scapulata)、0.008(H. mongolica)、0.004(H. sichuana)，种间的比对距离在0.024-0.045之间。对于ITS2，种内的比对距离分别为0.005(H. scapulata)、0(H. mongolica)、0.007(H. sichuana)，种间的比对距离在0.028-0.047之间。H. sichuana和新种间的比对距离在0.024-0.037(COI)和0.044(ITS2)。比对距离揭示出种内低于0.008，种间在0.024-1.078之间。因而，它们之间应该是种间关系而不是种内的关系。COI数据集和ITS2数据集所构建的系统树存在一定的差异，前者显示四川水龟甲和条纹水龟甲是姐妹种，后者显示新种和条纹水龟甲是姐妹种。总之，在内蒙古自治区发现的为一新的物种。

增温对川西北高寒草甸植物群落结构及几种主要植物生长和生理的影响

由于人类活动所引起的地球大气层中温室气体的富集已导致全球地表平均温度在20世纪升高了0.6 ℃，并预测在本世纪将上升1.4-5.8 ℃。气候变暖对陆地植物和生态系统影响深远，并已成为全球变化研究的重要议题。高海拔、高纬度地带的生态系统对气候变化最敏感。而在高原和高山极端环境影响下所形成的高寒草甸生态系统极其脆弱，对由于温室效应引起的全球气候变化极其敏感，对这些变化的响应更具有超前性。 本研究以川西北高寒草甸植物群落及几种主要物种为研究对象，采用国际山地综合研究中心（ITEX）普遍所采用的增温方法-----开顶式生长室（OTC）模拟气候变暖来研究增温对高寒草甸植物群落结构、物质分配及其主要物种生长和生理的影响，以探讨高寒草甸植物响应与适应气候变暖的生物学和生态学机制。主要研究结论如下： 1、OTC的增温效果 由于地温、地表温度和气温的平均值在OTC内分别高出对照样地0.28℃、0.46℃和1.4℃，这说明本研究所采用的开顶式生长室（OTC）起到了增温的作用；同时，由于温室内与温室外接受的降水量相同，温室内由于热量条件的改善，土壤蒸发和植被的蒸腾作用增强，直接导致了OTC内土壤表层相对湿度的减少。 2、群落结构对增温的响应 由于增温时间较短，增温内外样地的物种组成并未发生改变；但增温后一定程度上改变了植物群落的小气候环境，从而导致物种间的竞争关系被破坏，种间竞争关系的破坏引起群落优势种组成发生相应的改变，在对照样地，鹅绒委陵菜、甘青老鹳草、遏蓝菜和蚤缀是占绝对优势的物种，而在OTC内，小米草、尼泊尔酸模、垂穗披碱草、发草和羊茅的重要性显著增加。 禾草和杂草由于对增温的生物学特性及其资源利用响应的不同，加之增温造成土壤含水量下降等环境因子的改变。与对照样地相比较，OTC内禾草的盖度及生物量都显著增加，而杂草的盖度和生物量则显著下降。 3、植物生长期对增温的响应 OTC内立枯和调落物的生物量在生长季末（10月份）都要小于对照样地的立枯和调落物生物量，而OTC内的地上鲜体生物量在10月份却略高于对照样地。这说明OTC内植物的衰老或死亡得以延缓，而植物的生长期得以延长。 4、群落生物量及分配对增温的响应 OTC内的地上鲜体生物量(10月份除外)和地下0-30cm的根系生物量与对照样地相比较，都出现了不同程度的减少；土壤根系的分配格局也发生了明显的改变，其中，OTC内0-10cm土层的生物量分配比例增加，而20-30cm土层生物量分配比例的减少。 5、群落碳、氮对增温的响应 增温后，OTC内植物群落地上活体和地下活根的碳浓度不同程度的高于对照样地，植物群落的碳库在OTC内也略高于对照样地；而OTC内植物群落地上活体和地下活根的氮浓度不同程度的低于对照样地，其植物群落的氮库与对照样地相比也略有下降。 6、几种主要植物的生长及物质分配对增温的响应 垂穗披碱草在增温后株高、比叶面积和地上生物量均显著地增加；尼泊尔酸模在增温后比叶面积和单株平均生物量积累显著地增加，而各组分中，增温处理使叶的生物量显著增加，而根的生物量却显著下降；鹅绒委陵菜在增温后株高、比叶面积和单株平均生物量积累显著地减少，而各组分中，增温处理使叶和茎的生物量显著减少，根的生物量却显著地增加。 尼泊尔酸模的LMR、RMR、R/S、根部碳含量、碳和氮在叶片与根部的分配比例在增温后显著地增加，而SMR、根部氮含量、碳和氮在茎部的分配比例在增温后却显著地降低；鹅绒委陵菜的RMR、R/S、碳和氮在根部的分配比例在增温后显著地增加，而SMR、LMR、碳在叶片的分配比例在增温后却显著地降低 7、几种主要植物的光合生理过程对增温的响应 增温使垂穗披碱草和尼泊尔酸模叶片中的叶绿素a、叶绿素b、总叶绿素含量显著增加；而鹅绒委陵菜叶片的叶绿素a、叶绿素b、总叶绿素含量在增温后显著减少，类胡萝卜素含量在增温后却显著增加。 增温对3种植物的气体交换产生了显著影响。其中，垂穗披碱草和尼泊尔酸模叶片的光响应曲线在增温后明显高于对照处理，A、E、gs、Pmax、、Rday、AQY和LSP显著增加，而LCP则显著降低；鹅绒委陵菜的光响应曲线在增温后则明显的低于对照处理，A、E、gs、Pmax、、Rday、AQY和LSP显著减少，而LCP则显著增加。 增温后垂穗披碱草和尼泊尔酸模叶片的Fv/Fm、Yield和qP显著增加；而鹅绒委陵菜叶片的Fv/Fm、Yield和qP则显著减少，qN却显著地增加。 8、几种主要植物的抗氧化酶系统对增温的响应 增温使垂穗披碱草和尼泊尔酸模体内抗氧化酶活性和非酶促作用有所提高，植物膜脂过氧化作用降低；鹅绒委陵菜叶片中酶促反应和非酶促反应在增温后也显著提高，但可能由于增温后的土壤干旱超过了鹅绒委陵菜叶的抗氧化保护能力，抗氧化酶活性及非酶促反应（脯氨酸、类胡萝卜素）的提高不足以完全清除干旱诱导形成的过量活性氧，因此叶片的膜脂过氧化程度仍然显著提高。 Enrichment of atmospheric greenhouse gases resulted from human activities such as fossil fuel burning and deforestation has increased global mean temperature by 0.6 ℃ in the 20th century and is predicted to increase in this century by 1.4-5.8 ℃. The global warming will have profound, long-term impacts on terrestrial plants and ecosystems. The ecoologcial consequences arising from global warming have also become the very important issuses of global change research. The terrestrial habitats of high-elevation and high-latitude ecosystems are regarded as the most sensitive to changing climate. The alpine meadow ecosystme, which resulted from the composite effects of mountain extreme climatic factors in Tibetan Plateau, is thus thought to be especially vulnerable and sensitive to global warming. In this paper, the response of plant community and several main species in the alpine meadow of Northewst Sichuan to experimemtal warming was studied by using open-top chambers (OTC). The aim of the this study was to research the warming effects on plant community structure, substance allocation, growth and physiological processes of several mian species, and to explore the biological and ecological mechanism of how the alpine meadow plants acclimate and adapt to future global warming. The results were as follows: 1. Warming effects of OTC The mean soil temperature, soil surface temperature and air temperature in OTC manipulation increased by 0.28℃、0.46℃ and 1.4℃ compared to the control during the growing season. This suggested that the OTC used in our study had increased temperature there. Meanwhile, the OTC manipulation slightly altered thermal conditions, but the same amount of precipitation was supplied to both the OTC manipulation and the control, so higher soil evaporation and plant transpiration in OTC manipulation directly lead to the decrease of soil surface water content. 2. The reponse of community structure to experimental warming The species richness was not changed by the short-term effect of OTC manipulation. However, experimental warming changed the microenvironment of plant community, therefore competitive balances among species were shift, leading to changes in species dominance. In the present study, the dominant plant species in the control plots were some forbs including Potentilla anserine, Geranium pylzowianum, Thlaspi arvense and Arenaria serpyllifolia, however, the importance value of some gramineous grasses including Elymus nutans, Deschampsia caespitosa, Festuca ovina, and some forbs including Euphrasia tatarica and Rumex acetosa significantly increased in OTC. The different biology characteristics and resource utilizations between gramineous grasses and forbs, and enhanced temperature caused change in some environment factors such as soil water content. As a result, the coverage and biomass of gramineous grasses significantly increased in OTC compared to the control, however, the coverage and biomass of forbs singnifciantly decreased in OTC compared to the control. 3. The reponse of plant growing season to experimental warming Both the standing dead and fallen litter biomass in OTC were lower than those in the control in October, and the biomass of aboveground live-vegetation in OTC was higher than that of the control. The results indicated that the senescence of plants was postponed, and the growing season was prolonged in our research. 4. The reponse of community biomass accumulation and its allocation to experimental warming Experimental warming caused the decrease of aboveground live biomass and belowground root biomass except for the aboveground live biomass in October. Experimental warming also had pronounced effects on the pattern of root biomass allocation. In the present study, the root biomass in 0-10cm soil layer increased in OTC manipulation compared to the control, however, the root biomass in the 20-30cm soil layer decreased in OTC manipulation compared to the control. 5. The reponse of community C and N content to experimental warming The C concentration and stock in aboveground live and belowground root both increased in OTC manipulation compared to the control. However, the N concentration and stock in aboveground live and belowground root both decreased in OTC manipulation compared to the control. 6. The reponse of gowth and biomass, C and N alloction of several species to experimental warming Experimental warming significantly increased the height, SLA (specific leaf area) and aboveground biomass of Elymus nutans in OTC manipulation compared to the control. The SLA and total biomass of Rumex acetosa also significantly increased in OTC manipulation compared to control, among the different components of Rumex acetosa, leaf biomass significantly increased, but root biomass significantly decreased in OTC manipulation compared to the control. However, the height, SLA and total biomass of Potentilla anserina significantly decreased in OTC manipulation compared to the control, among the different component of Potentilla anserina, leaf and stem biomass significantly decreased, but root biomass significantly increased in OTC manipulation compared to the control. The LMR (leaf mass ratio), RMR (root mass ratio), R/S (shoot/root biomass ration) and root C concentration of Rumex acetosa significantly increased in OTC manipulation compared to outside control, also, Rumex acetosa allocated relatively more C and N content to leaf and root in response to experimental warming, however, the SMR (stem mass ration) and root N concentration of Rumex acetosa significantly decreased in OTC manipulation compared to outside control, also, Rumex acetosa allocated relatively less C and N content to stem in response to experimental warming. The RMR and R/S of Potentilla anserina significantly increased in OTC manipulation compared to outside control, also, Potentilla anserina allocated relatively more C and N content to root in response to experimental warming, however, the SMR and LMR of Potentilla anserina significantly decreased in OTC manipulation compared to outside control, also, Potentilla anserina allocated relatively less C and N content to leaf in response to experimental warming. 7. The reponse of physiological processes of several species to experimental warming Experimental warming significantly increased chlorophyll a, chlorophyll b and total chlorophyll of Elymus nutans and Rumex acetosa in OTC manipulation compared to outside control. However, chlorophyll a, chlorophyll b, total chlorophyll and carotenoid of Potentilla anserina in OTC manipulation significantly decreased compared to outside control. Experimental warming had pronounced effects on gas exchange of Elymus nutans, Rumex acetosa and Potentilla anserine. In the present study, warming markedly increased the light response curves of Elymus nutans and Rumex acetosa in OTC manipulation compared to outside control, and also singnificantly increased A (net photosynthesis rate), E (transpiration rate), gs (stomatal conductance), Pmax (maximum net photosynthetic rate), Rday (dark respiration rate), AQY (apparent quantum yield) and LSP (light saturation point), but LCP (photosynthetic light compensation) of Elymus nutans and Rumex acetosa in OTC manipulation singnificantly decreased compared to outside control. However, warming markedly decreased the light response curves of Potentilla anserina in OTC manipulation compared to outside control, and also singnificantly decreased A, E, gs, Pmax, Rday, AQY and LSP, but LCP of Potentilla anserina in OTC manipulation singnificantly increased compared to outside control. Experimental warming singnificantly increased the chlorophyll fluorescence kinetics parameters such as Fv/Fm, Yield and qP of Elymus nutans and Rumex acetosa and qN of Potentilla anserina in OTC manipulation, but Fv/Fm, Yield and qP of Potentilla anserina in OTC manipulation singnificantly decreased. 8. The reponse of antioxidative systems of several species to experimental warming Experimental warming tended to increase the activities of antioxidative enzymes and stimulate the role of non-enzymes of Elymus nutans and Rumex acetosa. As a result, MDA content of Elymus nutans and Rumex acetosa decreased. The activities of antioxidative enzymes and non-enzymes of Potentilla anserina also significantly increased in OTC manipulation, but more O2- was produced because of lower soil water content, and the O2- accumulation exceeded the defense ability of antioxidative systems and non-enzymes fuctions. As a result, MDA content of Potentilla anserine still increased in OTC manipulation compared to outside control.

不同放牧强度下高山草甸生态系统碳氮分布格局和循环过程研究

本研究针对川西北高山草甸缺乏科学管理，过度放牧导致草场退化，并由此引发的一系列生态环境问题，选取红原县瓦切乡1996 年草地承包后形成的四个放牧强度草场，即不放牧、轻度（1.2 头牦牛hm-1）、中度（2.0 头牦牛hm-1）和重度放牧（2.9 头牦牛hm-1），作为研究对象，研究了不同放牧强度对草地植物-土壤系统中碳、氮这两个最基本物质的分布格局和循环过程的影响，并探讨了放牧干扰下高山草甸生态系统的管理。 1．放牧对草地植物群落物种组成，尤其是优势种，产生了明显的影响。不放牧、轻度、中度和重度放牧草地群落物种数分别为22，23，26，20 种，群落盖度分别是不放牧96.2%＞中度93.6%＞轻度89.7%＞重度73.6%。随放牧强度的增加， 原植物群落中的优势种垂穗鹅冠草（ Roegneria nutans ）、发草（Deschampsia caespitosa）和垂穗披碱草（Elymus nutans）等禾草逐渐被莎草科的川嵩草（Kobresia setchwanensis）和高山嵩草（Kobresia pygmaea）所取代成为优势种。同时，随放牧强度的增加，高原毛茛（Ranunculus brotherusii）、狼毒（Stellera chamaejasme）、鹅绒委陵菜（Potentilla anserina）和车前（Plantagodepressa）等杂类草的数量也随之增加。 2．生长季6～9 月份，草地植物地上和地下生物量（0～30cm）都是从6 月份开始增长，8 月份达到最高值，9 月份开始下降。每个月份，通常地上生物量以不放牧为最高，重度放牧总是显著小于不放牧；地下生物量随放牧强度的增加表现为增加的趋势，通常重度和中度放牧显著高于不放牧和轻度放牧草地。不放牧、轻度、中度和重度放牧草地6～9 月份4 个月的植物总生物量平均值分别是1543、1622、2295 和2449 g m-2，但随放牧强度的增加越来越来多的生物量被分配到了地下部分，地下生物量占总生物量比例的大小顺序分别是重度88%＞中度82%＞轻度76%＞不放牧69%。生物量这种变化主要是由于放牧使得群落优势种发生改变而引起的，其分配比例的变化体现了草地植物对放牧干扰的适应策略。 3．植物碳氮贮量的季节变化类似与生物量的变化。每个月份，不同放牧强度间植物地上碳氮的贮量有所不同，一般重度放牧会显著减少植物地上碳氮贮量。植物根系(0～30cm)碳氮贮量随放牧强度的增加表现为增加的趋势，通常重度和中度放牧显著高于不放牧和轻度放牧草地。不放牧、轻度、中度和重度放牧草地6～9 月份4 个月的植物总碳平均值分别是547、586、847 和909 g m-2，根系碳贮量占植物总碳的比例大小顺序分别是重度88%＞中度82%＞轻度76%＞不放牧69%；放牧、轻度、中度和重度放牧草地6～9 月份4 个月的植物总氮平均值分别是17、17、23 和26 g m-2，根系氮贮量占植物总氮的比例大小顺序分别是重度79%＞轻度71%＞中度70%＞不放牧65%。 4. 土壤有机碳贮量（0～30cm）的季节变化表现为7 月份略有下降，8 月开始增加，9 月份达到的最大值。土壤氮贮量的季节变化表现为随季节的推移逐渐增加的趋势。增加的放牧强度不同程度的增加土壤有机碳氮的贮量。不放牧、轻度、中度和重度放牧6～9 月份4 个月的土壤有机碳贮量的平均值分别是9.72、10.36、10.62 和11.74 kg m-2，土壤氮贮量分别为1.45、1.56、1.66 和1.83 kg m-2。土壤中有机碳（氮）的贮量都占到了植物-土壤系统有机碳（氮）的90%以上，但不同放牧强度之间的差异不明显。 5. 土壤氮的总硝化和反硝化，温室气体N2O 和CO2 的释放率的季节变化表现为从6 月份开始增加，7 月份达到最大值，8 月份开始下降，9 月份降为最小值。增加的放牧强度趋向于增加土壤氮的总硝化和反硝化作用，温室气体N2O和CO2 的释放率，通常情况下，中度放牧和重度放牧显著地加强了这些过程。 6．垂穗鹅冠草（Roegneria nutans）和川嵩草（Kobresia setchwanensis）凋落物在不同放牧强度下经过1 年的分解，两种凋落物的失重率及其碳氮的损失率3都随放牧增加表现为增加的趋势。在同一放牧强度下，川嵩草凋落物的失重率和碳氮的损失率都高于垂穗鹅冠草凋落物。 7. 尽管重度放牧显著增加了土壤碳氮的贮量，但同时也显著降低了植被群落盖度，降低了植物地上生物量，因此，久而久之会减少植物向土壤中的碳氮归还率；与不放牧和轻度放牧相比，重度放牧又显著增加了土壤CO2 和NO2 的排放量，这是草地生态系统碳氮损失的重要途径。由此可见，对于这些地处青藏高原的非常脆弱的高山草甸生态系统，长期重度放牧不仅导致植物生产力降低，而且将导致草地生态系统退化，甚至造成土壤中碳氮含量减少。 Long-term overgrazing has resulted in considerable deterioration in alpine meadowof the northwest Sichan Province. In order to explore management strategies for thesustainability of these alpine meadows, we selected four grasslands with differentgrazing intensity (no grazing-NG: 0, light grazing-LG: 1.2, moderate grazing-MG: 2.0,and heavy grazing-HG: 2.9 yaks ha-1) to evaluate carbon, nitrogen pools and cyclingprocesses within the plant-soil system in Waqie Village, Hongyuan County, Sichuan Province. 1. Grazing obviously changed the plant species composition, especially ondominant plant species. Total number of species is 22, 23, 26, and 20 for NG, LG, MGand HG, respectively. Vegetation coverage under different grazing intensity ranked inthe order of 96.2% for HG＞93.6% for MG＞89.7% for LG＞73.6% for NG. Thedominator of HG community shifted from grasses-Roegneria nutans andDeschampsia caespitosa dominated in the NG and LG sites into sedges-Kobresiapygmaea and K. setchwanensis. At the same time, with the increase of grazingintensity, the numbers of forbs, such as Ranunculus brotherusii, Stellera chamaejasme,Potentilla anserine and Plantago depressa, increased with grazing intensity. 2. Over the growing season, aboveground and belowground biomass showed a 5single peak pattern with the highest biomass in August. For each month, abovegroundbiomass usually was the highest in the NG site and lowest in the HG site.Belowground biomass showed a trend of increase as grazing intensity increased and itwas significantly higher in the HG and MG site than in the NG and LG sites. Totalplant biomass averaged over the growing season is 1543, 1622, 2295 and 2449 g m-2for NG, LG, MG and HG, respectively. The proportion of biomass to total plantbiomass for NG, LG, MG and HG is 88%, 82%, 76% and 69%, respectively. Higherallocation ratio for is an adaptive response of plant to grazing. 3. Carbon and nitrogen storage in plant components followed the similar seasonalpatterns as their biomass under different grazing intensities. Generally, heavy grazingsignificantly decreases aboveground biomass carbon and nitrogen compared to nograzing. Carbon and nitrogen storage in root tended to increase as grazing increasedand they are significantly higher in the HG and MG sites compared to the LG and NGsite. Total Carbon storage in plant system averaged over the growing season is 547,586, 847 and 909 g m-2 for NG, LG, MG and HG, respectively, while 17, 17, 23 and 26g m-2 for nitrogen. The proportion of carbon storage in root to total plant carbon forNG, LG, MG and HG is 88%, 82%, 76%, 69%, respectively, while 65%, 71%, 70%and 79% for nitrogen. 4. Carbon storage in soil (0-30cm) decreased slightly in July, then increased inAugust and peaked in September. Nitrogen storage in soil tended to increase withseason and grazing intensity. Total Carbon storage in soil averaged over the growingseason is 9.72, 10.36, 10.62 and11.74 kg m-2 for NG, LG, MG and HG, respectively,while 1.45, 1.56, 1.66 and 1.83 for nitrogen. The proportion of carbon (nitrogen)storage in soil to plant-soil system carbon (nitrogen) storage for NG, LG, MG and HGis more than 90%, which is not markedly different among different grazing intensities. 5. Gross nitrification, denitrification, CO2 and N2O flux rates in soil increasedfrom June to July and then declined until September, all of which tended to increasewith the increase of grazing intensity. Generally, heavy and moderate grazing intensitysignificantly enhanced these process compared to no and light grazing intensity. 6. After decomposing in situ for a year, relative weight, carbon and nitrogen loss in the litter of Roegneria nutans and Kobresia setchwanensis tended to increase asgrazing intensity increased. Under the same grazing intensity, relative weight, carbonand nitrogen loss in the litter of Kobresia setchwanensis were higher than these in thelitter of Roegneria nutans. 7. Although heavy grazing intensity resulted in higher levels of carbon andnitrogen in plant and soil, it decreased vegetation coverage and aboveground biomass,which are undesirable for livestock production and sustainable grassland development.What is more, heavy grazing could also introduce potential carbon and nitrogen lossvia increasing CO2 and N2O emission into the atmosphere. Grazing at moderateintensity resulted in a plant community dominated by forage grasses with highaboveground biomass productivity and N content. The alpine meadow ecosystems inTibetan Plateau are very fragile and evolve under increasing grazing intensity by largeherbivores; therefore, deterioration of the plant-soil system, and possible declines insoil C and N, are potential without proper management in the future.