Plant Ecology

Plant Ecology

Plant Ecology

692 Pages ·2006·30.67 MB ·English

Plant Ecology

Ernst-Detlef Schulze · Erwin Beck · Klaus Mçller-Hohenstein


Plant Ecology Ernst-Detlef Schulze · Erwin Beck · Klaus Mçller-Hohenstein


Plant Ecology


With 506 Figures, most of them in colour, and 101 Tables


1 2 Professor Dr. Ernst-Detlef Schulze Translated by:


Max-Planck-Institute for Biogeochemistry


P.O. Box 100164 Gudrun Lawlor, FIL


07701 Jena Dr. Kirsten Lawlor


Germany Dr. David Lawlor


9 Burywick


Professor Dr. Erwin Beck Harpenden


Department of Plant Physiology Hertfordshire


University of Bayreuth AL5 2AQ


95440 Bayreuth UK


Germany


Professor Dr. Klaus Mçller-Hohenstein


Department of Biogeography


University of Bayreuth


95440 Bayreuth


Germany


Original title:


Ernst-Detlef Schulze/Erwin Beck/Klaus Mçller-Hohenstein, Pflanzenækologie


Copyright ° 2002 Spektrum Akademischer Verlag GmbH, Heidelberg


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31/3150 5 4 3 2 1 0±Printedonacid-freepaper Preface


Content: This textbook starts at the level of the sociates and last, but not least, our families.


cell and molecular aspects of plant responses to Without the support and help of many collea-


the environment, which is never stress free. gues, friends and coworkers, it would not have


Building on this molecular ecophysiology, the been possible to finish this book in time so that


organisation and regulation of metabolism of it does not contain chapters which are outdated


whole plants will be described from an autecolo- before publication. Particular thanks are given


gical perspective. In the following parts, this to Mrs Barbara Lçhker, without whose thorough


book deals with the interactions with other or- editorial work this book probably would have


ganisms at the level of the ecosystem. Finally, never been completed. For the critical reading of


geographical and long-term conditions for the individual chapters, for advice and pointers to


expansion and dynamics of plant populations the literature, the authors would like to thank


and species on earth are discussed. The book many colleagues, in particular: A. Arneth (Jena),


closes with the element cycles on earth and thus K. Beierkuhnlein (Bayreuth), C.M.P. Blum (Ut-


stresses the influence of man on original, so- recht), H. Bohnert (Urbana), U. Deil (Freiburg),


called natural ecosystems. W.H.O. Ernst (Amsterdam), S. Fettig (Bayreuth),


As the book covers several different concep- E.Gloor(Jena),G.Guggenberger(Halle),F.Haakh


tual levels, many aspects and facts will be illu- (Stuttgart), U. Heber (Wçrzburg), H.W. Heldt


minated from very different viewpoints: the cell, (Gættingen), J. Kaplan (Jena), O. Kolle (Jena),


the plant, the ecosystem, the zones of distribu- U.Kçper (Bayreuth), O.L. Lange (Wçrzburg),


tion and earth as a whole. Thus, the authors W.Larcher (Innsbruck), C. Neûhæfer and G. Or-


have tried to fully consider the enormous width lich (Bayreuth), C. Ploetz (Wuppertal), M. Popp


and complexity of plant ecology. (Vienna), R. Voeseneck (Utrecht), R. Scheibe


The reader: The textbook is aimed at advanced (Osnabrçck), W. Schulze (Tçbingen), E. Steudle


students and their teachers. Knowledge in var- (Bayreuth), C. Wirth (Jena) and W. Zech and


ious disciplines of natural sciences is expected, P.Ziegler (Bayreuth).


from molecular biology to the earth sciences. Special thanks are also extended to Springer-


The authors have tried to recommend textbooks Verlag for having translated the original German


and articles from the relevant literature in each book published by Spektrum Akademischer Ver-


chapter. This ªfurther readingº is intended to lag. Both publishers obliged most of the requests


deepen the relevant knowledge and to help de- by the authors in a constructive manner and re-


velop an understanding in relation to neighbour- spected the individuality of the authors, even


ing fields. Additionally, basic knowledge is revis- though they had to consider the homogeneity of


ited in concise box-type texts. Conceptual the final product.


knowledge is abstracted and strengthened in ex- The authors hope for a good reception of


tensive summaries at the end of each section. Plant Ecology by interested readers and welcome


Thanks: Writing this textbook has been a plea- constructive criticism in the knowledge that the


sure, but has also cost the authors much of the writing of a textbook about plant ecology in its


one commodity which they lack most: time. A entirety is an almost insurmountable task.


great deal of what could and should have been


done was left by the wayside. We therefore ask E.-Detlef Schulze, Erwin Beck and


all those whom we did not give enough of our Klaus Mçller-Hohenstein


time to make allowances, in particular our as- Bayreuth and Jena, October 2004 Contents


Introduction . . . . . . . . . . . . . . . . . . . . . . 1 1.5 Water Deficiency (Drought) . . 117


1.5.1 Water Balance of Drought-Stressed


Chapter 1 Cells . . . . . . . . . . . . . . . . . . . . . . . . 119


Stress Physiology . . . . . . . . . . . . . . . . . 5 1.5.2 Cellular Reactions to Drought Stress 123


1.5.3 CAM


(Crassulacean Acid Metabolism) . . . 135


1.1 Environment as Stress Factor:


1.5.4 Anatomical-Morphological Adapta-


Stress Physiology of Plants . . 7 tion to Drought . . . . . . . . . . . . . . . . 140


1.1.1 Abiotic and Biotic Environments


Cause Stress . . . . . . . . . . . . . . . . . . 7 1.6 Salt Stress (Osmotic Stress) . . 145


1.1.2 Specific and Unspecific Reactions


1.6.1 Physiological Effects of Salt Stress


to Stress . . . . . . . . . . . . . . . . . . . . . 9


(NaCl) . . . . . . . . . . . . . . . . . . . . . . . 146


1.1.3 Stress Concepts . . . . . . . . . . . . . . . . 11


1.6.2 Adaptive Responses of Plant Cells


1.1.4 Perception of Stress and Creation


to Salt Stress . . . . . . . . . . . . . . . . . . 149


of Signals . . . . . . . . . . . . . . . . . . . . 13


1.6.3 Avoidance of Salt Stress . . . . . . . . . 171


1.1.5 How to Measure Stress on Plants? . . 16


1.1.6 Production of Stress-Tolerant Plants


1.7 Heavy Metals . . . . . . . . . . . . . . . 175


by Genetic Engineering? . . . . . . . . . 16


1.7.1 Availability of Heavy Metals . . . . . . 176


1.1.7 Gene Silencing . . . . . . . . . . . . . . . . 19


1.7.2 Heavy Metal Deficiency ± Example


Iron . . . . . . . . . . . . . . . . . . . . . . . . . 176


1.2 Light . . . . . . . . . . . . . . . . . . . . . . . 23 1.7.3 Stress by Heavy Metal Ion Toxicity . 182


1.2.1 Visible Light . . . . . . . . . . . . . . . . . . 24 1.7.4 Reaction of Plants to Excess Supply


1.2.2 UV Radiation . . . . . . . . . . . . . . . . . 37 of Heavy Metals . . . . . . . . . . . . . . . . 184


1.7.5 Heavy Metal Resistance (Tolerance) 191


1.3 Temperature . . . . . . . . . . . . . . . . 45 1.7.6 Heavy Metal Extraction and Soil


1.3.1 Temperature Ranges and Tempera- Decontamination by Plants


tures Limiting Life . . . . . . . . . . . . . . 45 (Phytomining, Phytoremediation) . . 191


1.3.2 Temperature-Dependent Biochemical


Processes, Q and Activation Energy 48 1.8 Aluminium . . . . . . . . . . . . . . . . . 195


10


1.3.3 Temperature and Stability/Function 1.8.1 Forms of Aluminium Available to


of Biomembranes . . . . . . . . . . . . . . 49 Plants . . . . . . . . . . . . . . . . . . . . . . . 196


1.3.4 Heat (Hyperthermy) . . . . . . . . . . . . 50 1.8.2 Aluminium Toxicity . . . . . . . . . . . . 196


1.3.5 Cold . . . . . . . . . . . . . . . . . . . . . . . . 61 1.8.3 Al3+ Resistance . . . . . . . . . . . . . . . . 200


1.3.6 Frost . . . . . . . . . . . . . . . . . . . . . . . . 72 1.8.4 Al3+ Tolerance . . . . . . . . . . . . . . . . . 203


1.3.7 Concluding Comments . . . . . . . . . . 94


1.9 Xenobiotica . . . . . . . . . . . . . . . . . 207


1.4 Oxygen Deficiency 1.9.1 Herbicides . . . . . . . . . . . . . . . . . . . . 210


(Anaerobiosis and Hypoxia) . . 99 1.9.2 Gaseous Air Pollutants . . . . . . . . . . 215


1.4.1 Energy Metabolism of Plants Lacking


Oxygen . . . . . . . . . . . . . . . . . . . . . . 101


1.4.2 Anatomical-Morphological Changes


During Hypoxia . . . . . . . . . . . . . . . 105


1.4.3 Post-anoxic Stress . . . . . . . . . . . . . . 114 VIII Contents


1.10 Biotic Stress: Herbivory, 3.2 Processes in Stands and


Infection, Allelopathy . . . . . . . 235 Ecosystems . . . . . . . . . . . . . . . . . 403


1.10.1 Signal Chain in Wounding . . . . . . . 235 3.2.1 Self-Thinning . . . . . . . . . . . . . . . . . 403


1.10.2 Pathogen Attack and Defence . . . . . 246 3.2.2 Reversible and Irreversible Site


1.10.3 Allelopathy . . . . . . . . . . . . . . . . . . . 250 Changes Related to Resource


Exploitation . . . . . . . . . . . . . . . . . . 406


3.2.3 Complexity and Non-linear


Chapter 2 Behaviour . . . . . . . . . . . . . . . . . . . . 409


3.2.4 Number of Species and Habitat


Autecology: Whole Plant Ecology . . 253


Partitioning . . . . . . . . . . . . . . . . . . 411


3.2.5 Disturbances . . . . . . . . . . . . . . . . . 417


2.1 Thermal Balance of Plants . . 255


2.1.1 The Atmosphere as Habitat . . . . . . 257


3.3 The Biogeochemical Cycles . . 425


2.1.2 Climate of Air Near the Ground . . . 263


3.3.1 Water Turnover . . . . . . . . . . . . . . . 426


2.1.3 Energy Balance of Leaves . . . . . . . . 269


3.3.2 Carbon Turnover . . . . . . . . . . . . . . 427


2.1.4 Adaptation to Temperature


3.3.3 Nitrogen Cycle . . . . . . . . . . . . . . . . 438


Extremes . . . . . . . . . . . . . . . . . . . . 270


3.3.4 Cation Turnover . . . . . . . . . . . . . . . 444


2.2 Water Relations of Plants . . . 277


3.4 Biodiversity and Ecosystem


2.2.1 Water as an Environmental Factor . 277


Processes . . . . . . . . . . . . . . . . . . 449


2.2.2 Water Transport in the Plant . . . . . 283


2.2.3 Regulation of Stomata . . . . . . . . . . 296


3.5 Case Studies at the Scale


2.2.4 Transpiration of Leaves and


Canopies . . . . . . . . . . . . . . . . . . . . 303 of Ecosystems . . . . . . . . . . . . . . 455


3.5.1 Soil Acidification and Forest


2.3 Nutrient Relations of Plants . 313 Damage . . . . . . . . . . . . . . . . . . . . . 456


2.3.1 Availability of Soil Nutrients and Ion 3.5.2 Effect of Deciduous and Coniferous


Uptake . . . . . . . . . . . . . . . . . . . . . . 313 Forests on Processes in Ecosystems 460


2.3.2 Nitrogen Nutrition . . . . . . . . . . . . . 324 3.5.3 Plants of Limestone and Siliceous


2.3.3 Sulfur Nutrition . . . . . . . . . . . . . . . 335 Rocks . . . . . . . . . . . . . . . . . . . . . . . 462


2.3.4 Phosphate Nutrition . . . . . . . . . . . . 337


2.3.5 Nutrition with Alkaline Cations . . . 338


Chapter 4


2.4 Carbon Balance . . . . . . . . . . . . 347 Syndynamics, Synchorology,


2.4.1 Net Photosynthesis: Synecology . . . . . . . . . . . . . . . . . . . . . . . 465


Physiological and Physical Basis . . 347


2.4.2 Specific Leaf Area, Nitrogen Content 4.1 Historic-Genetic Development


and Photosynthetic Capacity . . . . . 357


of Phytocenoses and Their


2.4.3 Response of Photosynthesis


Dynamics . . . . . . . . . . . . . . . . . . 467


to Environmental Factors . . . . . . . . 361


4.1.1 History of Vegetation to the End


2.4.4 Growth and Storage . . . . . . . . . . . . 373


of the Tertiary . . . . . . . . . . . . . . . . 469


2.4.5 C and N Balance in Different Types


4.1.2 Change of Climate and Vegetation


of Plants . . . . . . . . . . . . . . . . . . . . . 379


in the Pleistocene . . . . . . . . . . . . . . 472


4.1.3 Late and Postglacial Climate and


Vegetation History . . . . . . . . . . . . . 475


Chapter 3


4.1.4 Changes in Vegetation Because of


Ecology of Ecosystems . . . . . . . . . . . . 397


Human Influence . . . . . . . . . . . . . . 479


4.1.5 Basis of General Vegetation


3.1 The Ecosystem Concept . . . . . 399 Dynamics . . . . . . . . . . . . . . . . . . . . 507


3.1.1 What is an Ecosystem? . . . . . . . . . . 400 4.1.6 Stability of Plant Communities . . . . 534


3.1.2 Boundaries of Ecosystems . . . . . . . 400


3.1.3 Compartmentalisation . . . . . . . . . . 401


3.1.4 System Characteristics . . . . . . . . . . 401 a Contents IX


4.2 Synchorology: Basis of Spatial 5.2.3 Nitrogen Cycle . . . . . . . . . . . . . . . . 636


Distribution of Plants . . . . . . . 541 5.2.4 Sulfur Cycle . . . . . . . . . . . . . . . . . . . 638


4.2.1 Distribution of Plants . . . . . . . . . . . 542


5.3 Human Influence on Carbon


4.2.2 Basis of Spatial Distribution


(Phytogeography) . . . . . . . . . . . . . . 548 Balance and Significance for


4.2.3 Relationship Between Area Global Climate . . . . . . . . . . . . . . 641


and Species . . . . . . . . . . . . . . . . . . . 555


4.2.4 Biodiversity . . . . . . . . . . . . . . . . . . . 562 5.4 Significance of Changes in


Land Use for Carbon Cycles . . 649


4.3 Interactions Between Vegeta-


5.4.1 Land Use and CO Emissions . . . . . 649


tion and Abiotic and Biotic 2


5.4.2 The Kyoto Protocol: Attempts To


Environments ± Synecology . . 579 Manage the Global Carbon Cycle . . 651


4.3.1 Influences of Vegetation on the Site 580 5.4.3 Importance of Climate Change


4.3.2 Interactions Between Plants and for Europe . . . . . . . . . . . . . . . . . . . . 659


Animals . . . . . . . . . . . . . . . . . . . . . . 585


4.3.3 Interactions Between Plants . . . . . . . 602 5.5 Influence of Human Activities


on Biodiversity . . . . . . . . . . . . . . 663


5.5.1 Decrease in Biodiversity . . . . . . . . . 663


Chapter 5


Global Aspects of Plant Ecology . . . 623 5.6 Socio-economic Interactions . 669


5.6.1 Syndromes . . . . . . . . . . . . . . . . . . . 670


5.1 Global Change and Global 5.6.2 Evaluation of Risks to Biodiversity


Institutions . . . . . . . . . . . . . . . . . 625 in Ecosystems . . . . . . . . . . . . . . . . . 673


5.2 Global Material Cycles . . . . . . . 633


5.2.1 Water Cycle . . . . . . . . . . . . . . . . . . . 633 Subject Index . . . . . . . . . . . . . . . . . . . . . 679


5.2.2 Carbon Cycle . . . . . . . . . . . . . . . . . . 635 Introduction


The term ªecologyº was defined by Ernst molecular stress physiology via ecology of whole


Haeckel in 1906 in his book, Principles of Gener- organisms and the ecosystem to the temporal


al Morphology of Organisms, as follows: ªEcol- and spatial differentiation of vegetation.


ogy is the science of relations of the organism Figure 1 shows the relations between (cellu-


to the surrounding environment which includes, lar) stress or ecophysiology, whole plant phys-


in its broadest sense, all `conditions for exis- iology and synecology (i.e. the ecology of vege-


tence'. These conditions may be organic or inor- tation cover) and ecosystem science where other


ganic; both are of the greatest importance for organisms, not only plants, are increasingly con-


the form of organisms, because they force the sidered. The interrelations between stress phy-


organism to adapt.º siology, whole plant physiology and synecology


Haeckel included in the science of ecology the are very close and obvious. In contrast, the path


areas physiology, morphology and chorology from stress physiology to ecosystems runs via


(the science of the distribution of organisms) to whole plant ecology and synecology because


understand the ªconditions for existenceº and morphology, i.e. the structure of plants, and the


ªadaptationº. In this book, we try to comply responses of populations are not primarily meta-


with Haeckel's understanding of plant ecology bolic. Applied ecology includes all disciplines


and to include the breadth of ecology as it was related to human activities. These include not


demanded by Haeckel. Adaptation to the envi- only agriculture and forestry, but also global


ronment starts at the molecular and cellular lev- change. Agriculture and forestry contain also


el where environmental conditions are detected physiological aspects of high-yielding and pest-


and the responses to changes in the environment free varieties of crops and the biological interac-


are accomplished. Starting from these physiolog- tions between crop plants and other organisms,


ical mechanisms, the morphological characteris-


tics of organisms/plants become important at


the level of the whole plant. Cellular metabolic


reactions and structural (morphological and an-


atomical) organisation are the biological ªtoolsº


with which organisms make use of certain envi-


ronmental conditions, avoid them or ªadaptº to


them. The combination of physiological and Ecology


morphological ªadaptationº is particularly im-


portant for plants, as they are fixed in their hab- Stress physiology


itat and the conditions for life are determined


by the variety and numbers of the organisms of


the ecosystem and not by the individual plant


Whole plant


alone. These environmental conditions and the Synecology


ecology


interaction of a plant with the environment de-


termine ªfitnessº, i.e. the possibility for growth


and reproduction in a spatial and temporal di-


Ecology of ecosystems


mension, thus resulting in an association with


Haeckel's ªchorologyº. Haeckel's understanding


Applied ecology, global change


of ecology was broader than our present botani-


cal usage. The present book views ecology in as


nFig. 1. Areas of ecology and their position within bot-


broad a context as Haeckel did, ranging from


any,ecosystemstudiesandinappliedecology 2 Introduction


e.g. for pollination. Research on global change of these strategies, certain species are able to


also includes the assessment of possible manage- avoid extreme conditions and use or change


ment systems for earth with respect to their ef- their habitat. Annual plants form the largest


fects on climate and maintaining biodiversity. proportion of plant species in dry areas. How-


Research on global change leads to model pre- ever, their active life is limited to favourable


dictions on future effects of human activities. conditions after rain, even if this only occurs


In this book, an attempt is made, for the first sporadically, perhaps only every few years or


time, to bring together and clearly organise the even decades. In contrast, perennial species have


large subdisciplines of plant ecology. We start mechanisms that regulate the water relations


from the molecular stress and ecophysiology of and enable survival in unfavourable climatic


plants in the broadest analysis yet attempted. periods. These include, for example, special leaf


Chapter 1 lays down the molecular basis for and root anatomy that allows the species to sur-


ecological ªadaptationsº to all essential environ- vive with intact shoot systems or to change their


mental factors. This ranges from climatic factors site conditions. Hydraulic lift, for example, en-


via salt stress in the soil to environmental pollu- ables roots to transport water from deep soil


tants. The stress theory considers the basic pos- layers to the upper horizons and thus moisten


sibilities of stress responses resulting from the upper soil layers. In temperate climates, the


strains and leading to resistance; finally, these accumulation of carbon in the soil changes site


provide the basis for understanding adaptive ra- fertility. The scope for ªadaptationsº by whole


diation of genotypes, and the processes leading plants is very broad, as are the responses of cells


to the evolution of new species. Plants not only to stress. They range from leaf structure and


react to stress in the sense of a response, the so- leaf movement, via the formation of variably di-


called feed-back reponse. There are also pre- mensioned vessels in the stem, to differentiation


paratory adaptations to changing environmental of the roots. In Chapter 2, the use of resources


conditions, the so-called feed-forward reactions, by whole plants is discussed. This includes the


setting off before an organism is stressed (e.g. plant±water relations, the heat and nutrient bal-


pre-winter frost hardening). In both cases, signal ances and the carbon relations.


chains are activated, leading to changes in the Cellular metabolism and structural character-


physiological/cell biological performance of istics are not only the basis for the spatial and


plants, enabling them to continue to exist under temporal patterns of plant species, dealt within


new conditions. The response to one stress fac- synecology (Chap. 4), but also the basis for ele-


tor often protects the organism also from dam- ment cycles in ecosystems, which are charac-


age by other stresses (ªcross-protectionº). This terisedbythediversityofspeciesandformsofor-


results in responses to a variety of stresses re- ganisation.Theseincludeindirectinteractionsbe-


sulting from a changing environment where not tween individual plants and other plant species.


one single factor (e.g. heat or drought), but mul- Here applies the wisdom that: ªEven the most


tiple stress types are acting in combination. The pious cannot live in peace if it does not please


basic principles of avoidance (as a sort of feed- the nasty neighbourª. Competition exists in the


forward response) and tolerance (as a sort of effective use of resources on limited space. If the


feed-back response) to stress are not only re- resources become scarce, ªefficiencyº means a


stricted to the level of ecophysiology, but occur better use of limiting resources at the cost of


also in responses of wholeplants, inthe distribu- the neighbour. This, of course, does not always


tionofspeciesandplantcommunities,particular- imply saving resources or using them most eco-


ly at extreme sites. nomically. Indeed, it may be more useful to use


At the level of the organism, we consider the more resources than required, if this brings ad-


plant as a whole and the relations between its vantages in competition with the neighbours.


organs from the root to the leaf, flower and Growth also plays an important role in ecosys-


seed. At the level of whole plant ecology new, tems, and the ªecological equilibriumº of an eco-


not (primary) metabolic characteristics are system probably does not exist in ªnatureº as it


added: although these are genetically deter- is. Metabolic cycles in ecosystems are not as


mined, they may be modified within limits. closed as previously assumed. This means that


These include plant structures including size the actual status as it may be observed as a mo-


and the life cycle (phenology, life span, strate- mentary picture of a system is in the long term


gies for reproduction and distribution). Because verydynamic. Not allprocesses ofasystemmove a Introduction 3


dry


alkaline


Limits of


a positive


shade


carbon balance


Flowering


and fruiting


possible


Without


competition


Temporal and


geographical


cold warm


range with


competition


acid


sunny


wet


nFig.2.Distributionofaspeciesdependsondifferentenvironmentalfactors.Theactualdistributionareaissignificantly


smaller thanthe potential areas ofdistribution whicharereachedwithoutcompetition attheextremelimits offlowering


or at the boundaries of a positive material balance. In the example shown, temperature is the dominant factor, but this


maydifferinothercases.Accordingtothespecies,thelimitsofdistributionchange


linearly in one direction.There are strengthening use of the available resources. In synecology, the


and weakening processes with a consequential broad spectrum of responses at the cellular and


complex, non-linear temporal behaviour. The sci- whole plant level is replaced by the enormous


entific basis of ecosystems is, for the first time, diversity of species (350,000 species of vascular


presented in Chapter 3 of this volume. General plants) which determine in different proportions


conclusions are drawn about how individual or- the composition of the vegetation cover of the


ganisms interact within the diversity of vegeta- earth. In Chapter 4, the historical and spatial di-


tion. This leads to the question about the degree mensions of species distributions and their bio-


towhichvegetationismorethanthesumofitsin- logical interactions are discussed.


dividualplants.Manycharacteristicsofvegetation Combining the ecology of ecosystems with


result from material fluxes which dictate the per- the field of synecology enables us to understand


formance of individual plants. For example, the also the distribution of species. Both the poten-


ªaero-dynamic roughnessº of the surface of vege- tial and actual areas (Fig. 2) are determined by


tation determines coupling to the meteorological several parameters. For example, considering


conditions in the atmosphere and thus deter- only the carbon balances, a plant species could


mines the survival of plant individuals or a spe- grow on a much larger area than the region in


cies inthe vegetation. It is only by large numbers which it actually reproduces. However, even this


of individuals of the same species which,through region is limited by different types of competi-


distribution of seeds or other ways of propaga- tion with other species, so that the area even-


tion, determine the habitat in relation to a dy- tually occupied is even further restricted. Agri-


namic diversity of other species. cultural crop plants (maize, beans, wheat, potato,


Synecology is the next higher level of plant soya and many others) are an interesting exam-


ecology, extending to populations based on the ple of evolution in a geographically limited area


strategies of propagation and distribution. Syn- (theso-calledgeneticcentres oforigin),butthese


ecology does not consider the fate of a single in- species are now distributed worldwide after do-


dividual, but the dynamic spatial and temporal mestication and management by humans.


behaviour of populations, including population The science of geobotany relates to global as-


growth, homoeostasis and decline. Only in ex- pects in plant ecology, which are included in the


ceptional cases does a single species form a veg- term global change, where the direct and indi-


etation. Generally, natural vegetation includes a rect influences of man through land use,


diversity of species which make complementary changes in land use and the subsequent changes


Ernst-Detlef Schulze · Erwin Beck · Klaus Mçller-Hohenstein


Plant Ecology Ernst-Detlef Schulze · Erwin Beck · Klaus Mçller-Hohenstein


Plant Ecology


With 506 Figures, most of them in colour, and 101 Tables


1 2 Professor Dr. Ernst-Detlef Schulze Translated by:


Max-Planck-Institute for Biogeochemistry


P.O. Box 100164 Gudrun Lawlor, FIL


07701 Jena Dr. Kirsten Lawlor


Germany Dr. David Lawlor


9 Burywick


Professor Dr. Erwin Beck Harpenden


Department of Plant Physiology Hertfordshire


University of Bayreuth AL5 2AQ


95440 Bayreuth UK


Germany


Professor Dr. Klaus Mçller-Hohenstein


Department of Biogeography


University of Bayreuth


95440 Bayreuth


Germany


Original title:


Ernst-Detlef Schulze/Erwin Beck/Klaus Mçller-Hohenstein, Pflanzenækologie


Copyright ° 2002 Spektrum Akademischer Verlag GmbH, Heidelberg


ISBN 3-540-20833-X Springer-Verlag Berlin Heidelberg New York


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31/3150 5 4 3 2 1 0±Printedonacid-freepaper Preface


Content: This textbook starts at the level of the sociates and last, but not least, our families.


cell and molecular aspects of plant responses to Without the support and help of many collea-


the environment, which is never stress free. gues, friends and coworkers, it would not have


Building on this molecular ecophysiology, the been possible to finish this book in time so that


organisation and regulation of metabolism of it does not contain chapters which are outdated


whole plants will be described from an autecolo- before publication. Particular thanks are given


gical perspective. In the following parts, this to Mrs Barbara Lçhker, without whose thorough


book deals with the interactions with other or- editorial work this book probably would have


ganisms at the level of the ecosystem. Finally, never been completed. For the critical reading of


geographical and long-term conditions for the individual chapters, for advice and pointers to


expansion and dynamics of plant populations the literature, the authors would like to thank


and species on earth are discussed. The book many colleagues, in particular: A. Arneth (Jena),


closes with the element cycles on earth and thus K. Beierkuhnlein (Bayreuth), C.M.P. Blum (Ut-


stresses the influence of man on original, so- recht), H. Bohnert (Urbana), U. Deil (Freiburg),


called natural ecosystems. W.H.O. Ernst (Amsterdam), S. Fettig (Bayreuth),


As the book covers several different concep- E.Gloor(Jena),G.Guggenberger(Halle),F.Haakh


tual levels, many aspects and facts will be illu- (Stuttgart), U. Heber (Wçrzburg), H.W. Heldt


minated from very different viewpoints: the cell, (Gættingen), J. Kaplan (Jena), O. Kolle (Jena),


the plant, the ecosystem, the zones of distribu- U.Kçper (Bayreuth), O.L. Lange (Wçrzburg),


tion and earth as a whole. Thus, the authors W.Larcher (Innsbruck), C. Neûhæfer and G. Or-


have tried to fully consider the enormous width lich (Bayreuth), C. Ploetz (Wuppertal), M. Popp


and complexity of plant ecology. (Vienna), R. Voeseneck (Utrecht), R. Scheibe


The reader: The textbook is aimed at advanced (Osnabrçck), W. Schulze (Tçbingen), E. Steudle


students and their teachers. Knowledge in var- (Bayreuth), C. Wirth (Jena) and W. Zech and


ious disciplines of natural sciences is expected, P.Ziegler (Bayreuth).


from molecular biology to the earth sciences. Special thanks are also extended to Springer-


The authors have tried to recommend textbooks Verlag for having translated the original German


and articles from the relevant literature in each book published by Spektrum Akademischer Ver-


chapter. This ªfurther readingº is intended to lag. Both publishers obliged most of the requests


deepen the relevant knowledge and to help de- by the authors in a constructive manner and re-


velop an understanding in relation to neighbour- spected the individuality of the authors, even


ing fields. Additionally, basic knowledge is revis- though they had to consider the homogeneity of


ited in concise box-type texts. Conceptual the final product.


knowledge is abstracted and strengthened in ex- The authors hope for a good reception of


tensive summaries at the end of each section. Plant Ecology by interested readers and welcome


Thanks: Writing this textbook has been a plea- constructive criticism in the knowledge that the


sure, but has also cost the authors much of the writing of a textbook about plant ecology in its


one commodity which they lack most: time. A entirety is an almost insurmountable task.


great deal of what could and should have been


done was left by the wayside. We therefore ask E.-Detlef Schulze, Erwin Beck and


all those whom we did not give enough of our Klaus Mçller-Hohenstein


time to make allowances, in particular our as- Bayreuth and Jena, October 2004 Contents


Introduction . . . . . . . . . . . . . . . . . . . . . . 1 1.5 Water Deficiency (Drought) . . 117


1.5.1 Water Balance of Drought-Stressed


Chapter 1 Cells . . . . . . . . . . . . . . . . . . . . . . . . 119


Stress Physiology . . . . . . . . . . . . . . . . . 5 1.5.2 Cellular Reactions to Drought Stress 123


1.5.3 CAM


(Crassulacean Acid Metabolism) . . . 135


1.1 Environment as Stress Factor:


1.5.4 Anatomical-Morphological Adapta-


Stress Physiology of Plants . . 7 tion to Drought . . . . . . . . . . . . . . . . 140


1.1.1 Abiotic and Biotic Environments


Cause Stress . . . . . . . . . . . . . . . . . . 7 1.6 Salt Stress (Osmotic Stress) . . 145


1.1.2 Specific and Unspecific Reactions


1.6.1 Physiological Effects of Salt Stress


to Stress . . . . . . . . . . . . . . . . . . . . . 9


(NaCl) . . . . . . . . . . . . . . . . . . . . . . . 146


1.1.3 Stress Concepts . . . . . . . . . . . . . . . . 11


1.6.2 Adaptive Responses of Plant Cells


1.1.4 Perception of Stress and Creation


to Salt Stress . . . . . . . . . . . . . . . . . . 149


of Signals . . . . . . . . . . . . . . . . . . . . 13


1.6.3 Avoidance of Salt Stress . . . . . . . . . 171


1.1.5 How to Measure Stress on Plants? . . 16


1.1.6 Production of Stress-Tolerant Plants


1.7 Heavy Metals . . . . . . . . . . . . . . . 175


by Genetic Engineering? . . . . . . . . . 16


1.7.1 Availability of Heavy Metals . . . . . . 176


1.1.7 Gene Silencing . . . . . . . . . . . . . . . . 19


1.7.2 Heavy Metal Deficiency ± Example


Iron . . . . . . . . . . . . . . . . . . . . . . . . . 176


1.2 Light . . . . . . . . . . . . . . . . . . . . . . . 23 1.7.3 Stress by Heavy Metal Ion Toxicity . 182


1.2.1 Visible Light . . . . . . . . . . . . . . . . . . 24 1.7.4 Reaction of Plants to Excess Supply


1.2.2 UV Radiation . . . . . . . . . . . . . . . . . 37 of Heavy Metals . . . . . . . . . . . . . . . . 184


1.7.5 Heavy Metal Resistance (Tolerance) 191


1.3 Temperature . . . . . . . . . . . . . . . . 45 1.7.6 Heavy Metal Extraction and Soil


1.3.1 Temperature Ranges and Tempera- Decontamination by Plants


tures Limiting Life . . . . . . . . . . . . . . 45 (Phytomining, Phytoremediation) . . 191


1.3.2 Temperature-Dependent Biochemical


Processes, Q and Activation Energy 48 1.8 Aluminium . . . . . . . . . . . . . . . . . 195


10


1.3.3 Temperature and Stability/Function 1.8.1 Forms of Aluminium Available to


of Biomembranes . . . . . . . . . . . . . . 49 Plants . . . . . . . . . . . . . . . . . . . . . . . 196


1.3.4 Heat (Hyperthermy) . . . . . . . . . . . . 50 1.8.2 Aluminium Toxicity . . . . . . . . . . . . 196


1.3.5 Cold . . . . . . . . . . . . . . . . . . . . . . . . 61 1.8.3 Al3+ Resistance . . . . . . . . . . . . . . . . 200


1.3.6 Frost . . . . . . . . . . . . . . . . . . . . . . . . 72 1.8.4 Al3+ Tolerance . . . . . . . . . . . . . . . . . 203


1.3.7 Concluding Comments . . . . . . . . . . 94


1.9 Xenobiotica . . . . . . . . . . . . . . . . . 207


1.4 Oxygen Deficiency 1.9.1 Herbicides . . . . . . . . . . . . . . . . . . . . 210


(Anaerobiosis and Hypoxia) . . 99 1.9.2 Gaseous Air Pollutants . . . . . . . . . . 215


1.4.1 Energy Metabolism of Plants Lacking


Oxygen . . . . . . . . . . . . . . . . . . . . . . 101


1.4.2 Anatomical-Morphological Changes


During Hypoxia . . . . . . . . . . . . . . . 105


1.4.3 Post-anoxic Stress . . . . . . . . . . . . . . 114 VIII Contents


1.10 Biotic Stress: Herbivory, 3.2 Processes in Stands and


Infection, Allelopathy . . . . . . . 235 Ecosystems . . . . . . . . . . . . . . . . . 403


1.10.1 Signal Chain in Wounding . . . . . . . 235 3.2.1 Self-Thinning . . . . . . . . . . . . . . . . . 403


1.10.2 Pathogen Attack and Defence . . . . . 246 3.2.2 Reversible and Irreversible Site


1.10.3 Allelopathy . . . . . . . . . . . . . . . . . . . 250 Changes Related to Resource


Exploitation . . . . . . . . . . . . . . . . . . 406


3.2.3 Complexity and Non-linear


Chapter 2 Behaviour . . . . . . . . . . . . . . . . . . . . 409


3.2.4 Number of Species and Habitat


Autecology: Whole Plant Ecology . . 253


Partitioning . . . . . . . . . . . . . . . . . . 411


3.2.5 Disturbances . . . . . . . . . . . . . . . . . 417


2.1 Thermal Balance of Plants . . 255


2.1.1 The Atmosphere as Habitat . . . . . . 257


3.3 The Biogeochemical Cycles . . 425


2.1.2 Climate of Air Near the Ground . . . 263


3.3.1 Water Turnover . . . . . . . . . . . . . . . 426


2.1.3 Energy Balance of Leaves . . . . . . . . 269


3.3.2 Carbon Turnover . . . . . . . . . . . . . . 427


2.1.4 Adaptation to Temperature


3.3.3 Nitrogen Cycle . . . . . . . . . . . . . . . . 438


Extremes . . . . . . . . . . . . . . . . . . . . 270


3.3.4 Cation Turnover . . . . . . . . . . . . . . . 444


2.2 Water Relations of Plants . . . 277


3.4 Biodiversity and Ecosystem


2.2.1 Water as an Environmental Factor . 277


Processes . . . . . . . . . . . . . . . . . . 449


2.2.2 Water Transport in the Plant . . . . . 283


2.2.3 Regulation of Stomata . . . . . . . . . . 296


3.5 Case Studies at the Scale


2.2.4 Transpiration of Leaves and


Canopies . . . . . . . . . . . . . . . . . . . . 303 of Ecosystems . . . . . . . . . . . . . . 455


3.5.1 Soil Acidification and Forest


2.3 Nutrient Relations of Plants . 313 Damage . . . . . . . . . . . . . . . . . . . . . 456


2.3.1 Availability of Soil Nutrients and Ion 3.5.2 Effect of Deciduous and Coniferous


Uptake . . . . . . . . . . . . . . . . . . . . . . 313 Forests on Processes in Ecosystems 460


2.3.2 Nitrogen Nutrition . . . . . . . . . . . . . 324 3.5.3 Plants of Limestone and Siliceous


2.3.3 Sulfur Nutrition . . . . . . . . . . . . . . . 335 Rocks . . . . . . . . . . . . . . . . . . . . . . . 462


2.3.4 Phosphate Nutrition . . . . . . . . . . . . 337


2.3.5 Nutrition with Alkaline Cations . . . 338


Chapter 4


2.4 Carbon Balance . . . . . . . . . . . . 347 Syndynamics, Synchorology,


2.4.1 Net Photosynthesis: Synecology . . . . . . . . . . . . . . . . . . . . . . . 465


Physiological and Physical Basis . . 347


2.4.2 Specific Leaf Area, Nitrogen Content 4.1 Historic-Genetic Development


and Photosynthetic Capacity . . . . . 357


of Phytocenoses and Their


2.4.3 Response of Photosynthesis


Dynamics . . . . . . . . . . . . . . . . . . 467


to Environmental Factors . . . . . . . . 361


4.1.1 History of Vegetation to the End


2.4.4 Growth and Storage . . . . . . . . . . . . 373


of the Tertiary . . . . . . . . . . . . . . . . 469


2.4.5 C and N Balance in Different Types


4.1.2 Change of Climate and Vegetation


of Plants . . . . . . . . . . . . . . . . . . . . . 379


in the Pleistocene . . . . . . . . . . . . . . 472


4.1.3 Late and Postglacial Climate and


Vegetation History . . . . . . . . . . . . . 475


Chapter 3


4.1.4 Changes in Vegetation Because of


Ecology of Ecosystems . . . . . . . . . . . . 397


Human Influence . . . . . . . . . . . . . . 479


4.1.5 Basis of General Vegetation


3.1 The Ecosystem Concept . . . . . 399 Dynamics . . . . . . . . . . . . . . . . . . . . 507


3.1.1 What is an Ecosystem? . . . . . . . . . . 400 4.1.6 Stability of Plant Communities . . . . 534


3.1.2 Boundaries of Ecosystems . . . . . . . 400


3.1.3 Compartmentalisation . . . . . . . . . . 401


3.1.4 System Characteristics . . . . . . . . . . 401 a Contents IX


4.2 Synchorology: Basis of Spatial 5.2.3 Nitrogen Cycle . . . . . . . . . . . . . . . . 636


Distribution of Plants . . . . . . . 541 5.2.4 Sulfur Cycle . . . . . . . . . . . . . . . . . . . 638


4.2.1 Distribution of Plants . . . . . . . . . . . 542


5.3 Human Influence on Carbon


4.2.2 Basis of Spatial Distribution


(Phytogeography) . . . . . . . . . . . . . . 548 Balance and Significance for


4.2.3 Relationship Between Area Global Climate . . . . . . . . . . . . . . 641


and Species . . . . . . . . . . . . . . . . . . . 555


4.2.4 Biodiversity . . . . . . . . . . . . . . . . . . . 562 5.4 Significance of Changes in


Land Use for Carbon Cycles . . 649


4.3 Interactions Between Vegeta-


5.4.1 Land Use and CO Emissions . . . . . 649


tion and Abiotic and Biotic 2


5.4.2 The Kyoto Protocol: Attempts To


Environments ± Synecology . . 579 Manage the Global Carbon Cycle . . 651


4.3.1 Influences of Vegetation on the Site 580 5.4.3 Importance of Climate Change


4.3.2 Interactions Between Plants and for Europe . . . . . . . . . . . . . . . . . . . . 659


Animals . . . . . . . . . . . . . . . . . . . . . . 585


4.3.3 Interactions Between Plants . . . . . . . 602 5.5 Influence of Human Activities


on Biodiversity . . . . . . . . . . . . . . 663


5.5.1 Decrease in Biodiversity . . . . . . . . . 663


Chapter 5


Global Aspects of Plant Ecology . . . 623 5.6 Socio-economic Interactions . 669


5.6.1 Syndromes . . . . . . . . . . . . . . . . . . . 670


5.1 Global Change and Global 5.6.2 Evaluation of Risks to Biodiversity


Institutions . . . . . . . . . . . . . . . . . 625 in Ecosystems . . . . . . . . . . . . . . . . . 673


5.2 Global Material Cycles . . . . . . . 633


5.2.1 Water Cycle . . . . . . . . . . . . . . . . . . . 633 Subject Index . . . . . . . . . . . . . . . . . . . . . 679


5.2.2 Carbon Cycle . . . . . . . . . . . . . . . . . . 635 Introduction


The term ªecologyº was defined by Ernst molecular stress physiology via ecology of whole


Haeckel in 1906 in his book, Principles of Gener- organisms and the ecosystem to the temporal


al Morphology of Organisms, as follows: ªEcol- and spatial differentiation of vegetation.


ogy is the science of relations of the organism Figure 1 shows the relations between (cellu-


to the surrounding environment which includes, lar) stress or ecophysiology, whole plant phys-


in its broadest sense, all `conditions for exis- iology and synecology (i.e. the ecology of vege-


tence'. These conditions may be organic or inor- tation cover) and ecosystem science where other


ganic; both are of the greatest importance for organisms, not only plants, are increasingly con-


the form of organisms, because they force the sidered. The interrelations between stress phy-


organism to adapt.º siology, whole plant physiology and synecology


Haeckel included in the science of ecology the are very close and obvious. In contrast, the path


areas physiology, morphology and chorology from stress physiology to ecosystems runs via


(the science of the distribution of organisms) to whole plant ecology and synecology because


understand the ªconditions for existenceº and morphology, i.e. the structure of plants, and the


ªadaptationº. In this book, we try to comply responses of populations are not primarily meta-


with Haeckel's understanding of plant ecology bolic. Applied ecology includes all disciplines


and to include the breadth of ecology as it was related to human activities. These include not


demanded by Haeckel. Adaptation to the envi- only agriculture and forestry, but also global


ronment starts at the molecular and cellular lev- change. Agriculture and forestry contain also


el where environmental conditions are detected physiological aspects of high-yielding and pest-


and the responses to changes in the environment free varieties of crops and the biological interac-


are accomplished. Starting from these physiolog- tions between crop plants and other organisms,


ical mechanisms, the morphological characteris-


tics of organisms/plants become important at


the level of the whole plant. Cellular metabolic


reactions and structural (morphological and an-


atomical) organisation are the biological ªtoolsº


with which organisms make use of certain envi-


ronmental conditions, avoid them or ªadaptº to


them. The combination of physiological and Ecology


morphological ªadaptationº is particularly im-


portant for plants, as they are fixed in their hab- Stress physiology


itat and the conditions for life are determined


by the variety and numbers of the organisms of


the ecosystem and not by the individual plant


Whole plant


alone. These environmental conditions and the Synecology


ecology


interaction of a plant with the environment de-


termine ªfitnessº, i.e. the possibility for growth


and reproduction in a spatial and temporal di-


Ecology of ecosystems


mension, thus resulting in an association with


Haeckel's ªchorologyº. Haeckel's understanding


Applied ecology, global change


of ecology was broader than our present botani-


cal usage. The present book views ecology in as


nFig. 1. Areas of ecology and their position within bot-


broad a context as Haeckel did, ranging from


any,ecosystemstudiesandinappliedecology 2 Introduction


e.g. for pollination. Research on global change of these strategies, certain species are able to


also includes the assessment of possible manage- avoid extreme conditions and use or change


ment systems for earth with respect to their ef- their habitat. Annual plants form the largest


fects on climate and maintaining biodiversity. proportion of plant species in dry areas. How-


Research on global change leads to model pre- ever, their active life is limited to favourable


dictions on future effects of human activities. conditions after rain, even if this only occurs


In this book, an attempt is made, for the first sporadically, perhaps only every few years or


time, to bring together and clearly organise the even decades. In contrast, perennial species have


large subdisciplines of plant ecology. We start mechanisms that regulate the water relations


from the molecular stress and ecophysiology of and enable survival in unfavourable climatic


plants in the broadest analysis yet attempted. periods. These include, for example, special leaf


Chapter 1 lays down the molecular basis for and root anatomy that allows the species to sur-


ecological ªadaptationsº to all essential environ- vive with intact shoot systems or to change their


mental factors. This ranges from climatic factors site conditions. Hydraulic lift, for example, en-


via salt stress in the soil to environmental pollu- ables roots to transport water from deep soil


tants. The stress theory considers the basic pos- layers to the upper horizons and thus moisten


sibilities of stress responses resulting from the upper soil layers. In temperate climates, the


strains and leading to resistance; finally, these accumulation of carbon in the soil changes site


provide the basis for understanding adaptive ra- fertility. The scope for ªadaptationsº by whole


diation of genotypes, and the processes leading plants is very broad, as are the responses of cells


to the evolution of new species. Plants not only to stress. They range from leaf structure and


react to stress in the sense of a response, the so- leaf movement, via the formation of variably di-


called feed-back reponse. There are also pre- mensioned vessels in the stem, to differentiation


paratory adaptations to changing environmental of the roots. In Chapter 2, the use of resources


conditions, the so-called feed-forward reactions, by whole plants is discussed. This includes the


setting off before an organism is stressed (e.g. plant±water relations, the heat and nutrient bal-


pre-winter frost hardening). In both cases, signal ances and the carbon relations.


chains are activated, leading to changes in the Cellular metabolism and structural character-


physiological/cell biological performance of istics are not only the basis for the spatial and


plants, enabling them to continue to exist under temporal patterns of plant species, dealt within


new conditions. The response to one stress fac- synecology (Chap. 4), but also the basis for ele-


tor often protects the organism also from dam- ment cycles in ecosystems, which are charac-


age by other stresses (ªcross-protectionº). This terisedbythediversityofspeciesandformsofor-


results in responses to a variety of stresses re- ganisation.Theseincludeindirectinteractionsbe-


sulting from a changing environment where not tween individual plants and other plant species.


one single factor (e.g. heat or drought), but mul- Here applies the wisdom that: ªEven the most


tiple stress types are acting in combination. The pious cannot live in peace if it does not please


basic principles of avoidance (as a sort of feed- the nasty neighbourª. Competition exists in the


forward response) and tolerance (as a sort of effective use of resources on limited space. If the


feed-back response) to stress are not only re- resources become scarce, ªefficiencyº means a


stricted to the level of ecophysiology, but occur better use of limiting resources at the cost of


also in responses of wholeplants, inthe distribu- the neighbour. This, of course, does not always


tionofspeciesandplantcommunities,particular- imply saving resources or using them most eco-


ly at extreme sites. nomically. Indeed, it may be more useful to use


At the level of the organism, we consider the more resources than required, if this brings ad-


plant as a whole and the relations between its vantages in competition with the neighbours.


organs from the root to the leaf, flower and Growth also plays an important role in ecosys-


seed. At the level of whole plant ecology new, tems, and the ªecological equilibriumº of an eco-


not (primary) metabolic characteristics are system probably does not exist in ªnatureº as it


added: although these are genetically deter- is. Metabolic cycles in ecosystems are not as


mined, they may be modified within limits. closed as previously assumed. This means that


These include plant structures including size the actual status as it may be observed as a mo-


and the life cycle (phenology, life span, strate- mentary picture of a system is in the long term


gies for reproduction and distribution). Because verydynamic. Not allprocesses ofasystemmove a Introduction 3


dry


alkaline


Limits of


a positive


shade


carbon balance


Flowering


and fruiting


possible


Without


competition


Temporal and


geographical


cold warm


range with


competition


acid


sunny


wet


nFig.2.Distributionofaspeciesdependsondifferentenvironmentalfactors.Theactualdistributionareaissignificantly


smaller thanthe potential areas ofdistribution whicharereachedwithoutcompetition attheextremelimits offlowering


or at the boundaries of a positive material balance. In the example shown, temperature is the dominant factor, but this


maydifferinothercases.Accordingtothespecies,thelimitsofdistributionchange


linearly in one direction.There are strengthening use of the available resources. In synecology, the


and weakening processes with a consequential broad spectrum of responses at the cellular and


complex, non-linear temporal behaviour. The sci- whole plant level is replaced by the enormous


entific basis of ecosystems is, for the first time, diversity of species (350,000 species of vascular


presented in Chapter 3 of this volume. General plants) which determine in different proportions


conclusions are drawn about how individual or- the composition of the vegetation cover of the


ganisms interact within the diversity of vegeta- earth. In Chapter 4, the historical and spatial di-


tion. This leads to the question about the degree mensions of species distributions and their bio-


towhichvegetationismorethanthesumofitsin- logical interactions are discussed.


dividualplants.Manycharacteristicsofvegetation Combining the ecology of ecosystems with


result from material fluxes which dictate the per- the field of synecology enables us to understand


formance of individual plants. For example, the also the distribution of species. Both the poten-


ªaero-dynamic roughnessº of the surface of vege- tial and actual areas (Fig. 2) are determined by


tation determines coupling to the meteorological several parameters. For example, considering


conditions in the atmosphere and thus deter- only the carbon balances, a plant species could


mines the survival of plant individuals or a spe- grow on a much larger area than the region in


cies inthe vegetation. It is only by large numbers which it actually reproduces. However, even this


of individuals of the same species which,through region is limited by different types of competi-


distribution of seeds or other ways of propaga- tion with other species, so that the area even-


tion, determine the habitat in relation to a dy- tually occupied is even further restricted. Agri-


namic diversity of other species. cultural crop plants (maize, beans, wheat, potato,


Synecology is the next higher level of plant soya and many others) are an interesting exam-


ecology, extending to populations based on the ple of evolution in a geographically limited area


strategies of propagation and distribution. Syn- (theso-calledgeneticcentres oforigin),butthese


ecology does not consider the fate of a single in- species are now distributed worldwide after do-


dividual, but the dynamic spatial and temporal mestication and management by humans.


behaviour of populations, including population The science of geobotany relates to global as-


growth, homoeostasis and decline. Only in ex- pects in plant ecology, which are included in the


ceptional cases does a single species form a veg- term global change, where the direct and indi-


etation. Generally, natural vegetation includes a rect influences of man through land use,


diversity of species which make complementary changes in land use and the subsequent changes


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