Study Questions forAgroecosystems 2050:
1) What are the top 10 environmental challenges facing agriculture today?
2) Human population growth
3) Habitat loss, fragmentation, degradation
4) Fresh water quality and quantity
5) Threat of disease - plant and animal
6) unsustainable agricultural production
7) air pollution
8) degradation of marine habitats
9) Global climate change
10)Invasive species (plants animals)
2) Define the Greenhouse effect?
- some of the radiant heat from the Sun is captured in the lower atmosphere of the earth maintaining tem-
- gases that cause this are water vapor, carbon dioxide, methane, nitrous oxide and a variety of manufac-
- chemicals emitted from natural sources or anthropogenic activity
- past several decades the concentrations of these GHGs is rising -
3) Define Biodiversity:
- the degree of variation of life forms within a given species, ecosystems, biome or entire planet
- it is used as a measure of health of ecosystems
4) Describe the relationship between biodiversity and energy:
- biodiversity provides a niche space for excess energy in the environment to go to (excess energy from the
green house effect - which otherwise becomes heat
5) What are some ways to deal with erosion? (#1 problem facing agriculture)
- plant cover crops
- no till/reduced till
6) What is the carrying capacity of the earth?
7) How much water does a corn crop that produces 9 tones per hectare require during the growing season?
- 6 million liters
8) What are the challenges with an aquifer?
- use is split by city and agriculture
9) How is “tragedy of the commons” a description of water use from aquifers?
- tragedy of the commons definition = depletion of a shared resource by individuals, acting independently
and rationally, to each ones self interest, despite their understanding that depleting the common resource
is contrary to the groups long term best interests.
- predicts excessive rates of depletion under common property situation
- ground water a common-pool resource
- no private incentive exists for any user to reduce consumption for long term water conservation -
if one does others can use resource for self - so all increase to avoid losing share
- we have used 2.9 billion acre ft since predevelopment
10) Define “Dead Zone” and describe the dead zone in the gulf of mexico:
- no energy flow, no economic value - hypoxic (no oxygen) cause by excessive nutrient pollution from human activities along with other factors
that deplete the oxygen required to support most marine life in bottom and near bottom of water. (in
ocean and lakes)
- 11,000 km sqrd in gulf of mexico is dead zone - largest in the states
- The Mississippi river, which is drainage area of 41% of continental U.S. dumps high nutrient
runoff (N and P) into this area.
- 70% a result of agricultural runoff - including the Midwest (heart of US agribusiness)
11) Describe the OgallalaAquifer
- unconfined aquifer
- underlies 111.4 million acres or 174, 000 miles including 8 states - colorado, Kansas, Nebraska, new
mexico, Oklahoma, south dakota, texas, and wyoming
- gently rolling terrain, moderate precipitation, with low natural recharge rate
12) Describe how the dead zone forms?
1) during spring sun heated freshwater runoff from Mississippi river creates barrier layer in gulf, cutting off
saltier water below from contact with oxygen in air
2) Nitrogen and phosphorus from fertilizer and sewage in the freshwater layer ignite huge algae booms -
when algae die, they sink to saltier water, below and decompose, using oxygen in deeper water
3) Starved from oxygen and cut off from resupply the deeper water becomes dead zone, fish avoid or die in
massive numbers, tiny organisms that form the vital base of gulf food chain also die. Water brings
respite but spring runoffs start cycle anew
13) Why are significant unintended consequences of agriculture overlooked of intentionally ignored?
- lack of economic or ecological feedback loops
14) Describe Traditional Scientific Forms ofAnalysis
- focus is on separating the individual pieces of what is being studied
- reductionist science: to break into constituent parts
15) Define Systems Thinking:
- paying attention to the “ripple affect” of decisions and actions
- fundamentally different from traditional science
- focuses on how the thing being studied interacts with other constituents of the system
- instead of isolating smaller and smaller components of the system, systems thinking works by expanding
its view to take into account larger and larger numbers of interactions.
16) What does systems thinking work best for>
- complex problems that involve many sectors
- reoccurring problems where past attempts have made the situation worse
- issues where an action affects environments e.g. nitrogen use
- problems where the solution is not obvious
17) What is the philosophical basis of modern agriculture?
- maximizing productivity, economic return and efficiency
18) Define ecosystem:
- a community of living organisms and nonliving physical and chemical components of the environment
such as soil, light, moisture and temperature that work together
19) What is an issue when describing or working with ecosystems
- questions of size: farm? landscape? watershed? biosphere?
- an ecosystem has no particular size because it consists of all biotic and abiotic factors within a well de-
fined area linked together as a functioning unit.
20) What is the agroecosystems? - a model for the functioning of an agricultural system within a larger ecosystem
- can be viewed as the human activity of agriculture including the social, economic and environmental im-
- scale will vary from individual plant soil micro-organism, crops, herds of domesticated animals, farm or
landscape level, level of agricultural economies
- the application of ecological science in design and management
- provides a framework to integrate ecology, economics and sociology
21) Compare the predicted temperature changes of the equator, canada and the arctic
- arctic 6 deg, Canada 4 deg, Equator 0 or 1 deg
22) How do agroecosystems differ from natural systems?
Agroecosystem Natural System
Control External - Productivity Internal via feedback loops
Successional State Early Successional states Moving towards later suc-
Nutrient Cycles Open: energy can go in and out aka Closed
there is free flow
- input energy into system (input of
nitrogen) fossil fuels, human ener-
gy, animal energy
Determined by the strength of inter-
System Composition and Artificially managed to maximize actions among biotic and abiotic
function yield factors
- evolution is largely but not exclu-
sively through artificial selection evolution through natural selection
- disturbed community; natural se-- history and succession of natural
lection held back community
Dominant Source of Nutri- Fertilizers - high nutrient flux Soil food web
- links between biotic and abiotic
Microhabitats Low diversity High diversity
- reduced in order to channel energy
and nutrient flow into crop species
(biodiversity helps dissipate energy)
Niches Mostly open; Mostly occupied
- making susceptible, system is vul-
nerable to invasive species, pests,
disease Agroecosystem Natural System
Short and linear Complex and web-like
Symbiotic relationships Few Common
System Stability Low High
System efficiency economics Energy and resources
23) What 3 variables describe ecosystem stability?
1) Resistance: ability to remain unchanged during a period of stress - aka maintain structure and function
2) Resilience: ability to return to original state following period of stress/ disturbance (elasticity)
3) Strength of Linkages - ex. food webs influenced by 1 & 2
24) How are ecosystem functions influenced by stability, give 5 reasons and define each?
1) resistance, resilience, strength of linkages
2) sustainability (long term) ability of system to maintain structure and function indefinitely
3) self organization: ability to ensure efficient flow of energy within the system
4) diversity: maintenance of species richness - optimizing functional groups of species
5) efficiency of production: described as output per unit input
25) DefineAgroecological efficiency:
- yield or net income per unit of resource
25) Describe ecosystem adaption (to stress)
- infinity sign split into 4 quadrants:
- growth phase (r-phase) then conservation phase (K phase) then release phase (theta symbol) then reorga-
nization phase (alpha phase) then growth phase.....
26) Briefly describe the relationship between stress and change:
- sever stress can lead to ecosystem distress syndrome
- EDS = the situation that arises when a balanced equilibrium of an ecosystem is disturbed by a
failure or disruption of an essential link(s) in its chain of being
- moderate stress drives change 27) What are the 7 distressed ecosystem parameters, discuss each?
1) Poor Nutrient Cycling - increase in unused nutrients leaking from the system (input/output inefficiency)
2) Reduced Community Diversity - reduction in species diversity
3) Successional Retrogression - increased invisibility with a shift to R selected species (early successional
species - reproduction occurs quickly i.e. weed)
4) Primary Productivity Changes - either increase or decrease - higher productivity with early successional
ecosystems with stress due to resource limitation
6) Increased disease incidence: stress reduces defensive capabilities, i.e. increased climate change = in-
creased invasive species
7) Amplitude of population fluctuations: with a decrease in species diversity and an increase in invasive
new species, there is a breakdown in stable linkages, a reduction in the complexity of food webs and a
loss of stability - allowing for outbreaks of certain species
- ex. bird watching - monitoring species; or sharks, spotted in areas never seen before
28) What is the difference between R selected species and K selected species?
- R= ruderal species = well adapted to stress and high frequencies of disturbance
- increased fecundity = high reproductive rate
- K Selected expends more energy for fewer reproductive offspring
29) What is the relationship between a stressed system and risk to management?
- increase risk to management because increased variability
30) What are 7 factors of a healthy agroecosystem
- optimize long term productivity (not necessarily maximize
- maximize resistance to environmental variability
- maximize resilience to disturbance - how quickly the system can bounce back and return to productive
state - includes speed of return
- minimize inputs - energy, chemicals, costs
- support human communities
- minimize negative environmental impacts
- maximize sensory and nutritional quality
31) How can we maximize resistance and resilience?
- intercrop/cover crop
- increase biodiversity
32) What are our expectations of the ecosystems
1) Support (8) : nutrient cycling, soil formation, primary productivity, energy flow, water supply, refugia,
genetic resources, pollination and gene flow, gas temperature and regulation
2) Provide (9): Food, Fresh water, Wood and Fibre, Fuel, water storage and retention, habitat for resident
and transient populations, source of unique biological materials, movement of floral gametes, regulation
of atmospheric gases
3) Regulate (4): Climate, Flood, Disease, Water
4) Cultural (4):Aesthetic, Spiritual, Educational, Recreational
33) List some agro-ecosystem services that promote well being:
1) Security - food, resource access
3) Basic Needs - food and shelter
4) Social and Community relations and cohesion
34) What is the major difficulty to do with ecosystem services?
- appraising their worth...what are the minimum requirements of these services 35) Describe the problem of determining value of agro-ecosystem services:
- ecosystem services are not fully “captured” in commercial markets or adequately quantified in terms of
comparable value, as a result they are not often considered from an economic nor policy perspective
36) What are the benefits of determining value for ecosystem services?
- highlight these services
- establish the economic magnitude of global ecosystems
- establish an initial framework for further analysis
- stimulate additional research and debate
37) What is the environmental conundrum?
-are moral and economic arguments mutually exclusive?
38) What is the estimated value for ecosystem services? and what are the implications of this value?
- 33 trillion US $ per year
- if this value were taken into account it would change the entire global pricing system
39) What is a climax community?
- non-stable, it continues to change
39) Define Disturbance:
- selection pressure - imposes a genetic response on a population
- a relative discrete event in time and space that alters the structure of populations and communities - caus-
es changes in resource availability or the physical environment
- major cause of long term fluctuations in the structure and functioning
40) What 4 factors is the impact of disturbance on an agrosystem dependent upon?
1) Severity - magnitude of change
3) Type, size timing - what stage crop is it?
4) Intensity - the power of input
41) What are novel disturbances?
- slow recovery or trigger new successional pathways
- unexpected or never occurred before
- no genetic history for resistance
42) Discuss the relationship between disturbance type, size and timing - in succession:
- size effects landscape structure which influences food webs and energy flow
- creates gaps of different successional strategies and trajectories
- Timing of disturbance will influence the impact
- eg. frost at bud impact
41) Define Severity, what is its relation to vegetation regrowth?
- refers to the magnitude of change in the physical environment or nutrient cycling caused
- major factor in determining rate and trajectory of vegetation development
42) Why is knowing trajectory helpful?
- allows for manipulation of development - knowledge of where you want development to go
43) Define Intensity:
- the amount of energy released per unit area
- eg lightning, fires, hurricanes, intense storms that cause flooding
44) Describe the trends in disturbance frequency: a
- highly variable - herbivory may occur continuously vs fire outbreaks
- Influenced by human activity
45) Define Seed Bank:
- represents history of field, stored seeds for the future
46) Describe the relationship between disturbance, the seed bank and species type?
- as disturbance decreases, seed bank is closer to the surface
- Agr: seed bank should sit near top (top 5cm) where they will be active
- thus no-till is good to control weeds
- level of disturbance will influence the type of species that is present, it increases the perennials present
47) Why is important to keep seeds near the soil top, for weed control?
- you can manipulate biological system by exposing unwanted seed to the microbial, insect full, harsher en-
vironment of the soil
48) How does level of disturbance influence species development?
- more carbon present, initial stock of organic matter
- increased H2O, light and nutrients supports increased growth rates, initial growth decrease
- forces secondary succession - which does not compliment agriculture - works against nature
- increased nitrogen
39) Define succession:
- process of 1) individual replacement and 2) a change in performance of individuals
- successional pathway is the temporal patter of vegetation change
- process of succession refers to the interaction that causes change i.e. disturbance
- “road to recovery”
39) What is the relationship between agriculture and succession?
- ag. imposes management to control succession and chaos
- all biological systems naturally tend to want chaos
- process in which there is a change in species and a change of performance from these individuals
39) How do you manage succession?
- Disturbance: major influx of energy affecting system - till
- puts pressure on weeds, insects, diseases
- changes resource availability or physical environment
- Herbicides - weed control
- wipes out plant communities to increase yield (another disturbance)
39) What processes drive succession?
1) Facilitation: early species facilitate the the invasion of later ones
- increase nitrogen, increase in soil, build soil structure
- “helping” “assisting”
2) Inhibition - existing plants prevent or inhibit establishment of subsequent species (caused by chemical,
biotic, physical means - inhibitory effect of litter)
- black walnut tree
3) Tolerance: refers to the ability of a species to tolerate low levels of resources such as nutrients and envi-
- shade in undergrowth - long lived species are more likely to tolerate than shortlived species eg.
43) What are the stages of succession?
1) Primary: involves a change from a community governed by the dynamics of colonization to one gov-
erned by competition for resources 2) Secondary: initial species present at location due to intact seed bank (or seed and seedling bank - in for-
43) Compare and contrast the characteristics of primary and secondary succession?
Species - early colonizers have small - differs from primary succession
seeds that can disperse long in that many of the initial plant
distance by wind species are already present on
- vascular plant species that fix site immediately after distur-
nitrogen frequently bance
- successional trajectory for veg- - seed bank - agriculture
etation is influenced strongly by - seed and seedling bank -
the initial colonizers = founder forestry
Carbon Balance - Net primary productivity (NPP) - carbon dynamics much greater
and decomposition rates are of- because it begins with an initial
ten greatest in mid succession stock of soil organic matter
- NPP is a measure of new plant - high availability of light, water
material produced annually and nutrients supports high
- NPP = photosynthetic rate- rate growth rates if early colonizing
of respiration species
Decomposition - decomposition rates are very
low because it is limited by the
rate of litter input
- low organic matter results in
low moisture holding capacity
- nitrogen availability limits plant - Higher nitrogen availability
growth and biomass accumula- - Initial plant growth is not gener-
tion ally limited by nutrients
- rate of nitrogen input governed
by establishment of nitrogen fix-
ing plants and bacteria
- litter from non-nitrogen fixing
plants becomes an increasingly
important source of nitrogen
mineralization Primary Secondary
- - loss of vegetation and plant
community structure increases
- low evapotranspiration rates
because of loss of vegetation
which would have transferred
water to the atmosphere
Energy Exchange - - high surface temperatures oc-
cur in energy successional sites
42) When is primary succession likely to reoccur? When is secondary succession likely to reoccur - give examples
- primary succession may reoccur when disturbance removes soil and organic matter (- i.e. volcano erup-
tion, mining (ecosystem goes back to beginning)
- secondary succession may occur if the disturbance removes above ground biomass but soil and organic
matter are left eg. tillage, fire, hurricanes
- seed bank is undisturbed
43) What causes the high surface temperatures in early successional sites
1. Low albedo - the reflecting power of the surface - it is the ration of the reflected radiation from surface to
incident radiation (short wave reflected from soil - high in energy)
2. Lack of vegetation prevents transfer of energy via evapotranspiration to the atmosphere
3. Lack of vegetation cover - i.e. smooth surface - of early successional sites minimizes wind turbulence that
would act to transport heat away from the soil surface.
44) What is succession Hierarchy
- Causes - processes - defining factors
45) What are the causes of succession?
1) Open sites become available
2) species are differentially available at the site
3) Species differ in performance ability to handle stress - environment, nutrient, competition, predation, al-
46) What are the processes of succession?
- identifies the ecological processes that contribute to succession - e.g. disturbance, competition, dispersal,
Causes Processes Defining Factors
Site availability Disturbance Type and frequency of
tillage Causes Processes Defining Factors
Differential Species Avail- Dispersal through space -Proximity to weed seed re-
Dispersal through time - Seed bank composition
Differential Species Perfor- Resource Availability -Fertilizer placement,
Ecophysiology - Emergence timing, growth
Competition with crops - Herbicide use and timing,
cultivar competitive ability
47) How is an understanding of the mechanisms of succession applicable to management?
- allows us to predict changes in plant community structure in response to management ex. no till manage-
- allow for the design of production practices to closely mimic nature
48) Can agricultural production mimic nature? Give examples
- intercropping in the tropics, polyculture, agroforestry
- requires knowledge in the field, soil natural species
- micro-application technology
- cover crops
48) Define Biodiversity:
- refers to all species of plants, animals and microorganism existing and interacting within an ecosystem
- includes diversity within species, between species and of ecosystems
- operates not only on a present day functional level, but also ensures agains future extinction as well as
evolutionary flexibility in regards to future climate change
49) Describe how biomass and diversity change in secondary succession?
- both grow and peak near maturity (top = biomass production, bottom = species diversity)
Species diversity increases with biomass production- to a level of maturity
- disturbance stands in opposition to this 50) What are some examples of ecosystem services provided by diversity that go beyond food, fiber, fuel and in-
- nutrient recycling, micro climate control, detoxification, water control
- buffer zones - water purification
51) What is the net result of biodiversity simplification for agriculture?
- the “artificial ecosystem” that requires constant human intervention
- productive but dependent on external inputs
52) How do we enhance functional diversity in agroecosystems as an ecological strategy to enhance sustainability?
- intercropping, agroforestry, rotations, covercrops, no till, composting, green manure, organic matter addi-
53) Name 7 components of biodiversity and their functions:
Pollinators Pollination; genetic introgession
Predators and Parasites Population regulation; biological control
Herbivores Biomass consumption; nutrient cycling
Non-crop vegetation Competition allelopathy, sources of natural enemies,
crop wild relatives
Earthworms Soil structure, nutrient cycling
Soil mesofauna Decomposition, predation nutrient cycling
Soil microfauna Nutrient cycling, disease suppression
54) What are two types of biodiversity?
1) Planned biodiversity - associated with crops and livestock and purposely included within the system
2) Associated biodiversity - includes all flora, fauna, decomposers etc from surrounding environments
55) What factors does the degree to which biodiversity can be achieved within an agroecosystem depend on?
1) The diversity of the vegetation within and around the agroecosystem?
2) The permanence of various crops
3) The intensity of management
4) The extent of the isolation of the agroecosystem from natural vegetation
56) What is the Intrinsic value of biodiversity?
- the value biodiversity has on its own, encompassing cultural, social, aesthetic and ethical benefits
57) What is the Utilitarian value of biodiversity?
- encompasses commercial benefit, refers to the use of diversity to provide inputs into consumption and
production processes 58) What is the future value of biodiversity?
- the belief that in the future a new value will be discovered, eg undiscovered genetic potential
59) What is the functional value of biodiversity?
- biodiversity contribute to ecosystem life support functions and the preservation of ecological structure and
60) What is the relationship between diversity and function?
- enhances ecosystem function because different species or genotypes preform slightly different functions
i.e. occupy different niches
- is neutral or negative in that there are many more species than there are functions and thus redundancy is
built into the system
- essential functions of an ecosystem such as primary production, requires a minimal level of diversity to
maximize efficiency; this is saturated at a relatively low number of species
61) Define Functional Group give ex:
- the minimum number of species required to perform an ecosystem function
- a set of species that have similar effects on a specific ecosystem function or service
- essential plant species that contribute in different ways to key ecosystem functions
- ex. a functional group able to exploit diff components of available resources by differences in
canopy structure to maximize light interception or diff root architectures to optimize capture of
water and nutrients
62) List 7 key functional groups:
2) Decomposers (bacteria, fungi)
6) Macrofauna - organisms that change the structure of soil - eg worms
7) Autotrophic bacteria - utilize sources of energy other than organic matter - these bacteria play a key role
in nutrient cycling
63) Define Key Species: - what particular function did species have in what way did that contribute to the ecosys-
63) Why is diversity so important when environmental change happens?
- redundancy may be important - genetic reserves
64) What is the impact of agricultural intensification on biodiversity and agroecosystem function?
1) Functionally diverse systems are more effective in retaining nutrients than less diverse systems - worms,
2) Loss of Pollinators - through habitat decline, bees, bats, flys,