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1、第九章 群落的动态Community Dynamics,群落的内部动态群落的演替地球上生物群落的进化,Glacier Bay,Alaska,群落的内部动态,包括季节变化和年际变化波动(fluctuation)：在不同年度之间生物群落常有的明显变动，只限于群落内部的变化，不产生群落的更替现象波动多数是由群落所在地区气候条件的不规则变动引起的其特点是群落区系成分的相对稳定性，群落数量特征变化的不定性以及变化的可逆性在波动中，群落在生产量、各成分的数量比例、优势种的重要值以及物质和能量的平衡方面会发生相应的变化,群落波动的类型,不明显波动：群落各成员的数量关系变化很小，群落外貌和结构基本保持不变摆动
2、性波动：群落成分在个体数量和生产量方面短期波动，与优势种的逐年交替有关偏途性波动：是气候和水分条件的长期偏离而引起一个或几个优势种明显变更的结果不同的生物群落具有不同的波动性特点。一般说来，木本植物占优势的群落较草本植物稳定一些；常绿木本群落要比夏绿木本群落稳定一些。在一个群落内部，许多定性特征（如种类组成、种间关系、分层现象等）较定量特征（如密度、盖度、生物量等）稳定一些；成熟的群落较之发育中的群落稳定,群落的形成条件,迁移(migration)：繁殖体的传播过程，是形成群落的首要条件，也是群落变化和演替的主要基础定居(ecesis)：植物繁殖体到达新地点后，开始发芽、生长和繁殖的过程竞争(
3、competition)：随着裸地上定居种类和个体数量的增加，个体间以及物种间对光、水、营养和空气等空间和营养物质的竞争,In 1794,Captain George Vancouver visited the inlet to what is today called Glacier Bay,Alaska,he could not pass beyond the inlet to the bay,however,because his way was blocker by a mountain of iceIn 1879,John Muir explored the coast of Ala
4、ska,he did not find the“mountains of ice”described by Vancouver,but found open water.He eventually found the glaciers,which had retreated to 30 to 40 km up the glacial valley since Vancouvers visit 85 years earlierIn 1916,William S.Cooper visited Glacier Bay,and saw the place as the ideal laboratory
5、 for the study of ecological succession,群落演替的概念,演替(succession)：群落变化过程中，由低级到高级，由简单到复杂，一个阶段接着一个阶段，一个群落代替另一个群落的自然演变现象。The gradual change in plant and animal communities in an area following disturbance or the creation of new substrate裸地：没有植物生长的地段原生裸地(primary bare area)：从来没有植物覆盖的地面，或者原来存在过植被，但被彻底消灭了的地段次
6、生裸地(secondary bare area)：原有植被已不存在，但原有植被下的土壤条件基本保留，甚至还有曾经生长在此的种子或其他繁殖体的地段原生演替(primary succession)：发生在原生裸地上的演替。Succession occurs on newly exposed geological substrates,not significantly modified by organisms次生演替(secondary succession)：发生在次生裸地上的演替。Succession occurs in areas where disturbance destroys a
7、community without destroying the soil,Primary succession,地衣苔藓,Primary succession at Glacier Bay,Alask,Species richness increased rapidly in the early years of succession and then more slowly during the later stages,approaching a possible plateau in species richnessNot all groups of plants increased
8、in diversity throughout succession,Change in plant species richness during primary succession at Glacier Bay,Alaska(data from Reiners,Worley,and Lawrence 1971),Secondary succession on an abandoned field in North Carolina,幼苗,Change in woody plant species richness during secondary forest succession in
9、 eastern North America(data from Oosting 1942),Change in number of breeding bird species during secondary forest succession(data from Johnston and Odum 1956),演替的类型,按发生的时间进程快速演替：几年内发生的演替，如：草原撂荒地上的演替长期演替：几十年或几百年的演替，如：森林采伐后的恢复演替世纪演替：以地质年代计算的演替Primary forest succession around Glacier Bay may require abo
10、ut 1500 years,and secondary forest succession on the Piedmont Plateau takes about 150 years,the successional change in rock intertidal communities occurred within about 1.5 years,and ecological succession within a desert stream occurs in less than 2 months,演替的类型,按引起演替的主导因素群落发生演替：在原生和次生裸地上发生内因生态演替：演替
11、是环境变化所决定，但环境变化是群落种类成分生命活动的结果，群落改变了生态环境外因生态演替：由环境条件的变化造成，但不是群落成分生活活动的结果,演替的类型,按基质的性质水生基质演替系列旱生基质演替系列按群落代谢特征自养性演替异养性演替我国刘慎谔教授的划分：时间演替空间演替植被类型发生演替,演替系列,生物群落的演替过程，从植物的定居开始，到形成稳定的植物群落为止的过程演替系列中的每一个明显的步骤，称为演替阶段或演替时期水生演替系列旱生演替系列,Did you ever see this?,Did you ever see this as well?,1.Submersed aquatic plan
12、ts in the deeper water.2.Emergent cattails（香蒲）and bulrushes（芦苇）rooted in the mud of shallow water.3.Willow thickets（柳树灌丛）along the banks of distant shoreline.4.Conifer forest（针叶林）in drier,well drained soil above the willow thickets.,湿草甸,灌丛沼泽,沼泽,水生演替系列 Hydrosere,裸底阶段,浮叶根生植物阶段,挺水植物和沼泽植物阶段,沉水植物阶段,水生演替系
13、列 Hydrosere,自由漂浮植物阶段：湖底为原生裸地，植物漂浮生长，死亡残体沉入湖底，湖岸雨水冲刷物也沉积湖底，逐渐提高湖底沉水植物阶段：湖底出现轮藻等，湖底有机质积累加快，抬升加快，其余一些高等植物大量出现，如金鱼藻、眼子菜等浮叶根生植物阶段：湖底日益变浅，浮叶根生植物出现，如莲等，残体进一步促进湖底抬升直立水生阶段：湖底大大变浅，挺水植物如芦苇等取代浮叶根生植物，使湖底迅速抬高湿生草本植物阶段：喜湿生的沼泽植物出现，如莎草科和禾本科中的湿生种类木本植物阶段：木本灌木出现，然后乔木出现，形成森林,Succession in stream communities,Rapid success
14、ion has been well documented in Sycamore Creek,Arizona,which has been studied for nearly two decades by Stuart Fisher and his colleagues(1982)The creek is a tributary of the Verde River,lies approximately 32 km northeast of Phoenix,Arizona,where it drains approximately 500 km2 of mountainous desert
15、terrain.Evaporation（蒸发）nearly equals precipitation（降雨量）within the Sycamore Creek catchment,so flows are generally low and often intermittent.However,the creek is subject to frequent flash floods with sufficient power to completely disrupt the community and initiate succession,Succession in Sycamore
16、Creek after floods,Two days after floods,the majority of the stream bottom consisted of bare sand with some patches of diatomsFive days after floods,diatoms covered about half the streambedWithin 13 to 22 days,diatoms almost completely covered the stream bottom,other algae,especially blue-green alga
17、e and mats consisting of a mixture of the green alga Cladophora and blue-green algae,appeared in significant quantities by day 35By day 63,the bottom of Sycamore Creek consisted of a patchwork of areas dominated by diatoms,blue-green algae,and mats of Cladophora and blue-green algaeThe diversity of
18、diatoms and other algae,as measured by H,leveled off after only 5 days,and then began to decline after about 50 daysMost macroinvertebrate species survived the flood,because the invertebrate community of the creek is dominated by insects whose adults are terrestrial,during the floods of August,many
19、adult insects were in the aerial stage and the flood passed under them,these adults were the source of most invertebrate recolonization of the flood-devastated creek,Algal species diversity during succession in Sycamore Creek,Arizona(data from Fisher et al.1982),旱生演替系列 Xerosere,地衣植物群落阶段：岩石表面无土壤，光照强，
20、温度变化大，贫瘠而干燥，最先出现地衣，分泌的有机酸腐蚀岩石，加上自然的风化，岩石表面出现含有机质的小颗粒，并逐渐增多苔藓植物群落阶段：地衣群落后期开始出现苔藓植物，能忍受极端干旱环境，生长可以积累更多的腐殖质，对岩石表面的改造作用更强烈，岩石颗粒变细小，松软层更厚，为土壤的发育和形成创造条件草本植物群落阶段：一些耐旱的高等植物侵入，对环境改造更强烈，小气候和土壤条件更有利于植物的生长灌木群落阶段：一些喜阳的灌木开始出现，常与高草混生乔木群落阶段：喜阳的树木增加，逐渐形成森林，最后形成与当地气候相适应的乔木群落，形成顶级群落,群落初生演替经历的地衣阶段、苔藓阶段、草本植物阶段、灌木阶段和森林阶段
21、,Secondary succession in temperate forests,Succession of plant species on abandoned fields in North Carolina.Pioneer species consist of a variety of annual plants.This successional stage is then followed by communities of perennials and grasses,shrubs,softwood trees and shrubs,and finally hardwood t
22、rees and shrubs.This succession takes about 120 years to go from the pioneer stage to the climax community,Succession in rock intertidal communities,The first species to colonize open space on intertidal boulders were a green alga in the genus Ulva and the barnacle（甲壳动物）Chthamalus fissusThe next arr
23、ivals were several species of perennial red algaeFinally,if there was no disturbance for 2 to 3 years,Gigartina canaliculata grew over the other species and dominated 60%to 90%of the space,Succession in number of macroinvertebrate and macroalgae species on intertidal boulders(data from Sousa 1979),控
24、制演替的主要因素,环境变化植物繁殖体的散布植物之间直接或间接的相互作用群落种类组成中新的植物分类单位不断发生人类活动,演替方向,进展演替(progressive succession)：生物群落的结构和种类成分由简单到复杂，群落对环境的利用由不充分到充分，群落的生产力由低到高，群落对外界环境的改造逐渐强烈。A succession where the community becomes complex and contains more species and biomass over time 逆行演替(regressive/retrogressive succession)：导致生物群落结
25、构简单化，不能充分利用环境，生产力逐渐下降，不能充分利用地面，对外界环境的改造轻微。A succession where the community becomes simplistic and contains fewer species and less biomass over time.Some retrogressive successions are allogenic in nature.For example,the introduction of grazing animals result in degenerated rangeland,Comparison of pla
26、nt,community,and ecosystem characteristics between early and late stages of succession,This dense marsh was completely washed away by a flash flood that roared down the canyon（峡谷）,演替过程的理论模型Mechanisms of succession,经典的演替观：每一演替阶段的群落明显不同于下一阶段的群落；前一阶段群落中物种的活动促进了下一阶段物种的建立个体论演替观：初始物种组成决定着群落演替后来的优势种。当代的演替观
27、强调个体生活史特征，物种对策，以种群为中心，和各种干扰对演替的作用。究竟演替的途径是单向性的，还是多途径的？初始物种组成对后来物种的作用如何？演替的机制如何？这些是当代演替观的活跃领域。,演替过程的理论模型Mechanisms of succession,促进模型(facilitation model)：物种替代是由于先来物种改变了环境条件，使它不利于自身生存，而促进了后来其他物种的繁荣，因此物种替代有顺序性、可预测性和具方向性Pioneer species modify the environment in such a way that it becomes less suitable f
28、or themselves and more suitable for species characteristic of later successional stages.In other words,these early successional species“facilitate”colonization by later successional species,Mechanisms of succession,抑制模型(inhibition model)：认为演替具有很强的异源性，因为任何一个地点的演替都取决于哪些植物种首先到达那里。植物种的取代不一定是有序的，每一个种都试图排
29、挤和压制任何新来的定居者，使演替带有较强的个体性。演替并不一定总是朝着顶极群落的方向发展，所以演替的详细途径是难以预测的该学说认为演替通常是由个体较小，生长较快，寿命较短的种发展为个体较大，生长较慢，寿命较长的种。显然，这种替代过程是种间的，而不是群落间的，因而演替系列是连续的而不是离散的The early occupants of an area modify the environment in a way that makes the area less suitable for both early and late successional species.Simply,early
30、arrivals inhibit colonization by later arrivals.Later successional species can only invade an area if space is opened up by disturbance of early colonists,Mechanisms of succession,耐受模型(tolerance model)：该模型介于促进模型和抑制模型之间。认为：早期演替物种先锋种的存在并不重要，任何种都可以开始演替。植物替代伴随着环境资源的递减，较能忍受有限资源的物种将会取代其他种。演替就是靠这些种的侵入和原来定居
31、物种的逐渐减少而进行的，主要决定于初始条件The initial stages of colonization are not limited to a few pioneer species;species colonizing early in succession do not facilitate colonization by species characteristic of later successional stages;successional species are simply those tolerant of environmental conditions ear
32、ly in succession;the climax community is established when the list of tolerant species has been exhausted,三类模型的共同点和区别,演替中的先锋物种最先出现，它们具有生长快，种子产量大，有较高的扩散能力等特点。这类易扩散和移植的物种一般对相互遮荫和根间竞争的环境是不易适应的，所以在三种模型中，早期进入物种都是比较易于被挤掉的重要的是演替的机制，即物种替代的机制，是促进？抑制？还是现存物种对替代影响不大？而演替机制决定于物种间的竞争能力,Alternative successional mec
33、hanisms(data from Connell and Slatyer 1977),Which of these models does the weight of evidence from nature support,Most studies of succession support the facilitation model,the inhibition model,or some combination of the two,Successional mechanisms in the rocky intertidal zone,Sousas experiments show
34、ed that ulva（石莼）(early successional species)strongly inhibits recruitment by red algae(middle successional species),the middle successional species inhibit late successional species,supporting the inhibition model for successionEarly successional species are more vulnerable to a variety of physical
35、and biological factors causing mortalityTurners experiments demonstrated obligate facilitation during intertidal succession,其余理论,适应对策演替理论（Adapting strategy theory）R对策种，适应于临时性资源丰富的环境；C对策种，生存于资源一直处于丰富状态下的生境中，竞争力强，称为竞争种；S对策种，适用于资源贫瘠的生境，忍耐恶劣环境的能力强，叫做耐胁迫种。Grime（1988）提出，RCS对策模型反映了某一地点某一时刻存在的植被是胁迫强度、干扰和竞争之
36、间平衡的结果。该学说认为，次生演替过程中的物种对策格局是有规律的，是可以预测的。一般情况下，先锋种为R对策，演替中期的多为C对策，而顶级群落中的种则多为S对策种,其余理论,资源比率理论（Resource ratio hypothesis）该理论认为，一个种在限制性资源比率为某一值时表现为强竞争者，而当限制性资源比率改变时，因为种的竞争能力不同，组成群落的植物种也随之改变。因此，演替是通过资源的变化而引起竞争关系变化而实现的,其余理论,等级演替理论（Hierarchical succession theory）该理论包含有三个层次第一是演替的一般性原因。即裸地的可利用性，物种对裸地利用能力的差异
37、，物种对不同裸地的适应能力第二是将以上的基本原因分解为不同的生态过程，比如裸地可利用性决定于干扰的频率和程度，种对裸地的利用能力决定于种的繁殖体生产力、传播能力、萌发和生长能力等第三个层次是最详细的机制水平，包括立地种的因素和行为及其相互作用，这些相互作用是演替的本质,演替顶级学说Climax theory,演替顶极(climax)是指每一个演替系列都是由先锋阶段开始，经过不同的演替阶段，到达中生状态的最终演替阶段a climax community,or climatic climax community,is a biological community of plants and ani
38、mals which,through the process of ecological succession the development of vegetation in an area over time has reached a steady state.This equilibrium occurs because the climax community is composed of species best adapted to average conditions in that areaclimax theory A theory that embraces the id
39、ea of successional development to an optimum sustainable vegetation community that is in equilibrium with its environment.Two conceptual models of climax vegetation exist:monoclimax and polyclimax,单元顶极论（monoclimax hypothesis）,Clements认为，在任何一个地区内，一般的演替系列的终点决定于该地区的气候性质，主要表现在顶极群落的优势种，能够很好地适应于地区的气候条件，这样
40、的群落称之为气候顶极群落在同一气候区内，无论演替初期的条件多么不同，植被总是趋向于减轻极端情况而朝向顶极方向发展，从而使得生境适合于更多的植物生长,多元顶极论（polyclimax theory）,认为：如果一个群落在某种生境中基本稳定，能自行繁殖并结束它的演替过程，就可看作顶极群落在一个气候区域内，群落演替的最终结果，不一定都汇集于一个共同的气候顶极终点，还有土壤顶级、地形顶级、火烧顶级、动物顶级等,顶极-格局假说（climax-pattern hypothesis）,该理论认为，在任何一个区域内，环境因子都是连续不断地变化的。随着环境梯度的变化，各种类型的顶极群落，如气候顶极、土壤顶极、地
41、形顶极、火烧顶极等，不是截然呈离散状态，而是连续变化的，因而形成连续的顶极类型，构成一个顶极群落连续变化的格局。在这个格局中，分布最广泛且通常位于格局中心的顶极群落，叫做优势顶极（prevailing climax），它是最能反映该地区气候特征的顶极群落，相当于单元顶极论的气候顶极。顶级群落的组成由土壤养分、湿度、坡度、光照等许多因素决定,演替与生态恢复,“生态恢复”指通过人工方法，按照自然规律，恢复天然的生态系统。“生态恢复”的含义远远超出以稳定水土流失地域为目的种树，也不仅仅是种植多样的当地植物，“生态恢复”是试图重新创造、引导或加速自然演化过程。人类没有能力去恢复出真的天然系统，但是我们
42、可以帮助自然，把一个地区需要的基本植物和动物放到一起，提供基本的条件，然后让它自然演化，最后实现恢复。因此生态恢复的目标不是要种植尽可能多的物种，而是创造良好的条件，促进一个群落发展成为由当地物种组成的完整生态系统。或者说目标是为当地的各种动物提供相应的栖息环境生态恢复的方法有物种框架方法和最大多样性方法,物种框架方法,指建立一个或一群物种，作为恢复生态系统的基本框架。这些物种通常是植物群落中的演替早期阶段（或称先锋）物种或演替中期阶段物种这个方法的优点是只涉及一个（或少数几个）物种的种植，生态系统的演替和维持依赖于当地的种源（或称“基因池”）来增加物种和生命，并实现生物多样性。因此这种方法最
43、好是在距离现存天然生态系统不远的地方使用，例如保护区的局部退化地区恢复，或在现存天然斑块之间建立联系和通道时采用,最大多样性方法,是尽可能地按照该生态系统退化以前的物种组成及多样性水平种植物种进行恢复，需要大量种植演替成熟阶段的物种，先锋物种被忽略这种方法适合于小区域高强度人工管理的地区，例如城市地区和农业区的人口聚集区。这种方法要求高强度的人工管理和维护，因为很多演替成熟阶段的物种生长慢，而且经常需要补植大量植物，因此需要的人工比较多,人工林,有人不仅将人工林看作是对日益增长的人类对木材和木纤维需求的解决途径,而且作为天然林丧失的一种补救。他们认为,人工林解决了人类对天然林的需求,从而对环境保护作出了贡献另一些人则认为,人工林是生物多样性的沙漠、水的消耗者、人类生计的破坏者和自然景观的毒瘤,复习思考题,相关概念：演替、原生演替、次生演替、进展演替、逆行演替、演替顶级原生演替与次生演替的区别水生演替与旱生演替系列的过程演替过程的主要模型演替理论对生态恢复的意义,
