Download Ecosystem

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