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Agricultural Ecology By Dr. Rensen Zeng Department of Ecology College of Agriculture South China Agricultural University Email: [email protected] Textbook: ECOLOGYPrinciples and Application (Bilingual teaching 双语教学) Textbook and References 教材与参考文献 Ecology:Principles and applications (Second Edition edited by J L Chapman and M J Reiss, Cambridge University Press,1999) (影印版,清华大学出版社,2001) Ecological Principles of Agriculture Edited by L E Powers and R McSorley, Delmar of Thomson Learning,2000) 骆世明,农业生态学Agroecology. 中国农业出版社,2001 •How an organism can survive, reproduce and interact with other organisms? How does the organism obtain its food? How do plants and animals protect themselves? What Is Ecology Ecology is a science which studies the interactions (relationships) between organisms and their environment. 研究生物和环境之间相互关系及其作用机理的学科 主菜单 主目录 退出 • For example an ecologist may ask: • How does the organism obtain its food? • Is a particular nutrient limiting its growth • numbers? • Is something else limiting its growth or numbers? • Does it reproduce in this site and if so how? • Is it absent from parts of the site due to some factor? • How and when do the young disperse? • What causes the death of the organisms? What is "Ecology"? • To the layperson, it often means "environmentalism", • but • ecology is the science that underlies the concern for the effects of humans on the earth. In 1866, Haeckel used the term oecology: • from • • • OIKOS household, home and LOGOS study of, science of • (=the study of the household of nature) Ecology Definition: • the study of the interrelationships between organisms and their environment • • (includes the study of distribution and abundance, but encompasses more than that, unless you take a very broad view of those two terms). Ecology is a broad science that overlaps with other disciplines Physiology Behavior Ecology Evolution Genetics Ecology also overlaps with the physical sciences--geology, meteorology, hydrology, etc. • Since ecology draws on all these fields, the ecologist must be a jack-of-all-trades, knowledgeable in many areas and able to integrate many perspectives and levels of analysis; the challenge is to use everything you have learned in any area and integrate it all. • Levels of biotic organization – Individual – Population – Community – Ecosystem • • Concept of Community Ecosystem concept Ecosystem organization ¾Biosphere ¾Ecosystems ¾Communities Biosphere Ecosystems Communities ¾Populations ¾Organisms Populations Organisms Fig. 4.2, p. 72 There are four major areas of ecological study, although there is overlap among them. • • • • Physiological/functional ecology Population ecology Community ecology Ecosystems • (Landscapes) • (Biosphere) • Physiological / functional ecology (autecology) • --studies adaptations of organisms to their environment; how physiology, morphology, structure, behavior, and other attributes of individuals affect their functioning and survival; • --basically the study of an organism and the way it functions in its environment • (including the physical environment and other organisms). Individuals • Individuals: Genetically uniform and usually discrete – Why does the organism occur where it does and how does it interact for growth, resource procurement and reproduction? – The discipline is called Autecology, Physiological Ecology • Population--a group of individuals of the same species that co-occur in time and space • The population is the basic unit of genetics and hence evolution. • Population ecology studies numbers, distributions, regulation of population size, competition, mating systems and reproductive behavior, and other interactions among individuals that affect population characteristics. • Population: Collection of individuals of a species isolated inbreeding and adapted to environment through genetic diversity. – The discipline is called Population Ecology • Community--is a group of populations that co-occur in time and space • Groups of organisms of several species that co-occur in the same area and inter-act through trophic or spacial relationships. Often characterized by one or more dominant species Eucalyptus and pinecommunity. Community ¾ Community ecology studies the physical structure of assemblages as well as interactions among populations, succession, predator-prey relationships, diversity, etc. ¾ The discipline is called Community Ecology ¾ A community maintains mutual relationships through competition stratification dependency What is an ecosystem? bounded ecological system consisting of all the organisms in an area and the physical environment with which they interact • Ecosystem--a community (or group of communities) and the abiotic environment functioning together. • Ecosystem ecologists often study nutrient flow between living and nonliving components of the system, energy flow through the system as a whole, climate, biogeochemical cycles. Ecosystem A basic unit of ecology defined as a system of living organism interacting with the physical, chemical, biological and sociological environment. A conceptual tool and it has no physical boundary. •英国植物生态学家A.G. Tanslay 1935 •生态系统 ecosystem 生态系统 Ecosystem 1935年A.G. Tansley最先提出生态系统的概念 生物与环境构成一个不可分割的整体。 One unit of organism community and its environment. The community of organisms could not separated from the particular environment in which they live. Ecosystem • The word ecosystem is a relatively recent term. Sir Arthur Tansley invented the word in 1935 to apply to a whole community of organisms and its environment as one unit. • Tansley realised that the community could not be separated from the particular environment in which it lived. Arthur Tansley (1871-1955), Journal of Ecology 1. Melded “Clementsian” and “Gleasonian” perspective 2. Objected to holism and organismal concept, but also objected to reductionism 3. Proposed the ECOSYSTEM as middle ground: a system made up of partially overlapping systems The Odums: Eugene (1913-2002), UFL and Howard (1922-), UGA 1. Introduced new ecosystem tools to ecologists 2. Used electrical circuits and cybernetics to describe ecosystems 3. Embraced Clements's “ecosystem as organism”, alienated evolutionary and pop ecologists Eugene Howard 生物 1 物质 Nutrient Organisms 2 能量 Energy 相互关系 Interactions 3 信息 Information 4 依赖与改善 Dependence 环境 and amendment Environment 生物与环境之间的相互关系 Interactions between organisms and environment 环境 Environment 1. 无机环境 Inorganic (physical) environment 2. 有机环境 Organic (biotic) environment Competition, predation, parasitism, cooperation The ecosystem, or biocoenose, consists of the community of organisms plus the associated physical environment. Ecosystem Ecology Study of interactions among organisms and their physical environment as an integrated system An emerging level of organization (not yet well-developed): • Landscape--all of the interacting communities, ecosystems in a region; somewhat more extensive than an ecosystem (but boundaries are nebulous). • Landscape ecologists study change in a heterogeneous land area comprised of interacting systems. The Biosphere The BIOSPHERE =Living organisms plus those regions of the earth where life occurs. Life is restricted to this thin layer of the earth but is not uniformly distributed. This is the area where energy, nutrients, and appropriate substrate (surfaces) are available. • BIOSPHERE--those regions of the earth inhabited by life; the sum of all the earth's ecosystems. • Oceans, streams and lakes, the land to a soil depth of a few meters, and the atmosphere up to a few kilometers. • There has been relatively little study on global scales, until recently. Now, climate change (greenhouse effect), deforestation, acid rain, spread of nuclear wastes, etc. are being studied a bit. There are five fundamental processes that occur in the biosphere: • 1. Energy flow; with some rare exceptions, life depends on energy from the sun • 2. Nutrient dynamics (storage, flow, and turnover in organisms and inorganic pools) • 3. Population dynamics (all things that affect numbers of organisms at any given time, e.g., weather, predation) • 4. Evolution (natural selection) • 5. Cultural evolution (transmittal of acquired experiences from one generation to the next by non-genetic means, primarily in Homo sapiens. • Energy flow, nutrient dynamics, and population dynamics are sufficient to account for systems as they operate at the present time • (i.e., in ecological time), • whereas evolution and cultural evolution are necessary to account for changes that occur over longer periods, • i.e., evolutionary time. Some key questions in ecology: • What regulates distribution and abundance of organisms? e.g., zonation patterns? • How much do species compete and interact? • How do specific environmental factors affect distributions? • How do plants interact with animals, etc.? e.g., what is the effect of herbivory (being eaten by animals) on plants? • How do parts of systems interact? e.g., how do living and non-living components of the biosphere interact? Ecology 生态学 • Ecologists are always aiming to understand how an organism fits into its environment • The environment is of supreme importance to an organism and its ability to exist in the environment where it lives will determine its success or failure as an individual In the widest sense: Study of plants and animals as they exist in their natural home Generally speaking: Study of all aspects of living organisms with respect to their existence in nature Specifically: Relationships of plants and animals with one another and with their environment These interactions are complex and they vary with time, space and the species involve. The Odums: Eugene (1913-2002), UFL and Howard (1922-), UGA 1. Introduced new ecosystem tools to ecologists 2. Used electrical circuits and cybernetics to describe ecosystems 3. Embraced Clements's “ecosystem as organism”, alienated evolutionary and pop ecologists Eugene Howard E.P. Odum 1952 Fundamentals of Ecology 生态学基础 • 研究生态系统结构和功能的学科 • It studies the structure, functions of ecosystems Key Concepts ¾Basic ecological principles ¾Major components of ecosystems ¾Matter cycles and energy flow ¾Ecosystem studies ¾Ecological services WHY STUDY ECOLOGY? • Plants form the basis of all lives on earth; they are the primary produces. Chlor., light • 6CO2 + 6H2O ----------------- C6H12O6 + 6CO2 + 6O2 Enzymes • The earth is a space ship with fixed supply of matters that must sustain us for a long journey. • These matters must be efficiently recycled and reused over and over through complex processes. Functional dynamics: Web of complex interactions and interdependencies among plants. Synergy: System whose components are tied together through interactions. Stability: Dynamic equilibrium. Diffuse boundaries: Gradual change in composition Ecology is a synthetic science seeking to comprehend the whole. • Ecology can be considered on a wide scale, moving from individual molecule to the entire global ecosystem. However, four identifiable subdivisions of scale are of particular interest, The Earth ’s Life -Support Systems Earth’s Life-Support ¾Troposphere Atmosphere Biosphere Vegetation and animals Soil Crust Rock ¾Stratosphere ¾Hydrosphere core Lithosphere ¾Lithosphere ¾Biosphere Mantle Crust Crust (soil and rock) Biosphere (Living and dead organisms) Hydrosphere (water) Lithosphere (crust, top of upper mantle) Atmosphere (air) Fig. 4.6, p. 74 Embranchment of Ecology 生态学的分支 Within ecology there are a number of fields, either focusing on specific areas of interest or using particular approaches to address ecological problem. 1. Organism difference: Plant, animal, microorganism, and human ecology 2. Environmental difference:Terrestrial, Ocean and lake ecology, etc. 按生物类别分为:动物生态学、植物生态学、微生 物生态学、人类生态学等 按环境性质分为:陆地、海洋、湖沼等生态学。 Stages of social development Idyllic life Urban life Ecological life Types of ecosystems Natural Managed Artificial Agricultural Ecology (Agroecology 农业生态学) • Agroecology is a branch of ecology in agriculture. It studies the structure, functions, regulation, and management of agricultural ecosystems. The aim is to develop sustainable agriculture. • 农业生态学是用生态学和系统论的原理和方法,将农 业生物与其自然环境作为一个整体,研究其中的相互 作用、协同演变,以及社会经济环境对其调节控制规 律,促进农业全面持续发展的学科。 Agricultural Ecosystem Interactions between agricultural components Agricultural Ecology Predict the sustainability of this system Adopt more sustainable practices on land not well suited to agricultural uses Advise governmental or non-governmental organizations promoting land conservation practices such as terracing, agroforestry, and carbon sequestration. Agricultural Ecology Excesses of early use and abuse of technology – ignoring the adverse side effects of the GR technologies – pesticide use on CG center exper. plots • Carson, Pimentel: Killing the World with Pesticides… (Silent Spring Syndrome) • Avery: Saving the World with Pesticides and Plastics Agricultural Ecology ¾ Understand and predict the properties of agricultural production systems in all of the relevant dimensions that have come to be represented by the concept of sustainability ¾ Make possible the transition to a science-based agricultural policy that is needed to make an efficient use of the agricultural resource base Agricultural Ecology The new science needed to understand agriculture as a managed ecosystem will be derived in part from the developments in science that are focused on understanding complex natural and human systems. Agricultural Ecology Agriculture as a Managed Ecosystem Hypothesis: Agriculture is best understood and predicted as a complex, dynamic system with spatially varying inputs and outputs that are the results of interrelated physical and biological processes and human decision making processes. Agriculture as a Managed Ecosystem Some key terms (1): ¾ system = a set of interrelated processes ¾ ecosystem = ecological processes ¾ managed vs. natural systems ¾ exogenous drivers ¾ endogenous variables Some key terms (2) ¾ state variables = stocks at a point in time ¾ flow variables = inputs and outputs from processes, units defined by processes ¾ feedback = two or more linked state or flow vars. ¾ temporal and spatial scale: defined by processes ¾ loosely and closely coupled systems ¾ integrated system Agriculture as a Managed Ecosystem Agroecosystems are typically modeled as a set of linked sub-models, each with its own sets of drivers, state variables, flow variables and processes. ¾ loosely coupled system: state or flow variables from one sub-model are drivers in other sub-models ¾ closely coupled system: states and processes from one sub-model are linked directly to processes in another sub-model ¾ integrated system: a single set of drivers, endogenous variables for all model components that can represent all of the feedbacks in the system Agriculture as a Managed Ecosystem Biogeophysical drivers Production States Soil Nutrients Crop Economic States Crop State Ecosystem Model Fertilizer applications Soil Moisture Environmental Impact Decision Fertilizer Decisions Crop Yield Economic Capital Model Economic drivers Figure 1. Agroecosystems Represented as Loosely or Closely Coupled Ecosystem and Economic Models. Dotted connectors represent feedbacks from system states to drivers in a loosely coupled model, dashed connectors represent feedbacks between processes in a closely coupled agroecosystem model. Ecological engineering Ecological engineering The nature of ecology • The only way to find out how any organism survives, reproduces and interacts with other organisms is to study it. This makes ecology a practical science. Three main approaches to the study of ecology 1. The simplest method is to observe and record the organism in its natural environment. 2. A second type of study is to carry out experiments in the field to find out how the organism reacts to certain changes in its surroundings. 3. A third approach involves bringing organisms into a con-trolled environment in a laboratory, cage or green-house. • This method is very useful as it is often easier to record information under controlled conditions. • Ecology is a practical science requiring observations and experiments to investigate organisms • No single study can hope to discover everything there is to know about the relationships between an organism and its environment. These relationships are so varied that different kinds of investigation are needed to study them. • Often both study in the natural environment and experiments in the laboratory are required to discover even part of the picture. • So we have a picture of ecology as a subject full of complexity where an organism has many different responses and needs. • Theoretically, therefore, there is an almost infinite amount to be discovered about the ecology of the world. Even after a century of ecological study we are just scratching the surface of possible knowledge. The study of ecology • An ecologist could start any study by asking the question: 'Why does this organism live or grow here and not there?'. • In simplified terms this is the question ecological investigations often try to answer. Questions? • Is a particular nutrient limiting its growth numbers? • Is something else limiting its growth or numbers? Does it reproduce in this site and if so how? • Is it absent from parts of the site due to some factor? • How and when do the young disperse? • What causes the death of the organisms? Experimental design • There are several things to consider when looking at reported experiments or when designing your own. • (1) Is there a 'control'? • A control group of organisms is treated in the same way as the experimental group, except for the factors being studied in the experiment. (2) Are there replicates in the experiment? • The confidence with which conclusions can be drawn from an experiment is increased by repeating it several times (having replicate experiments) and considering all the results together. (3) Are the right data being collected? • Sometimes the wrong data are collected from an experiment or wrong recordings made during observation of organisms in their natural surroundings. It may be difficult to decide in advance what information is valuable to the study, so the best advice is to collect as much as possible and select what to analyse later. (4) Are the data correctly interpreted? • Because data from ecological experiments are often quite variable and sometimes inconclusive, it is often quite difficult to interpret the results. • Occasionally classic mistakes are made, as was the case for the worker who moved a plant into a different locality. • Experimental design is extremely important and requires, wherever possible, controls replicates, the accurate collection of data and careful interpretation of results. Where are we today? ¾ Putting individualistic perspective within context of overlapping systems ¾ Increasing awareness that organisms cannot be “black-boxed” ¾ Understanding human-caused change in the earth system ¾ New tools—rapid analysis, isotopes, models, global networks