PowerPoint Presentation

							       Ecosystem Ecology:
Case studies on the Colorado Plateau

             FOR 479     BIO 479
             FOR 599     BIO 599

                Stephen C. Hart
     Self-proclaimed “Ecosystem Ecologist”
           School of Forestry, NAU
      What is an Ecosystem?

• A bounded ecological system
  consisting of all the
  organisms in an area and the
  physical environment with
  which they interact (Chapin
  et al. 2002)
• The sum of all of the
  biological and non-biological
  parts of an area that interact
  to cause plants to grow and
  decay, soil or sediments to
  form, and the chemistry of
  water to change (Aber &
  Melillo 2001)
        What is an Ecosystem?
• A community and its environment
  treated together as a functional
  system of complementary
  relationships, and transfer and
  circulation of energy and matter
  (Whittaker 1975)
• Any unit that includes all of the
  organisms (i.e., “the community”) in
  a given area interacting with the
  physical environment so that the
  flow of energy leads to clearly
  defined trophic structure, biotic
  diversity, and material cycles (i.e.,
  exchange of materials between
  living and nonliving parts) within the
  system (E. Odum 1971)
     Simple ecosystem model

Key Attributes:
•Biotic and abiotic
processes
•Pools and fluxes
 What is Ecosystem Ecology?
• the study of the interactions
  among organisms and their
  environment as an integrated
  system (Chapin et al. 2002)
• the study of the movement of
  energy and materials,
  including water, chemicals,
  nutrients, and pollutants, into,
  out of, and within ecosystems
  (Aber & Melillo 2001)
   Ecosystem
   Structure &
    Function
• Ecosystem Structure –
  The vertical and
  horizontal distribution of
  ecosystem components
  (e.g., vegetation ht.,
  distribution of plant
  biomass above and
  below ground, etc.)
• Ecosystem Function –
  processes that are
  conducted or evaluated
  at the ecosystem scale
  (e.g., NPP, nutrient
  uptake, actual
  evapotranspiration, etc.)
Interdisciplinary
1) ecosystem processes
are controlled by factors
traditionally in the
purview of separate
disciplines, and
2) questions in ecosystem
ecology cross broad
scales in space and time




The unique
contribution of
ecosystem ecology is
its focus on biotic and
abiotic factors as
interacting components
of a single integrated
system
Spatial
 scale
  Delineating Ecosystem Boundaries

• How do we decide where to draw the lines
  around an ecosystem?
• Depends on the scale of the question
  being asked
   – Small scale: e.g., soil core; appropriate for
     studying microbial interactions with the soil
     environment, microbial nutrient
     transformations
   – Stand: an area of sufficient homogeneity
     with regard to vegetation, soils,
     topography, microclimate, and past
     disturbance history to be treated as a
     single unit; appropriate questions include
     impact of forest management on nutrient
     cycling, effects of acid deposition on forest
     growth
     Delineating Ecosystem Boundaries

Natural Boundaries: ecosystems sometimes
 are bounded by naturally delineated borders
 (lawn, crop field, lake); appropriate questions
 include whole-lake trophic dynamics and
 energy fluxes (e.g., Lindeman 1942)

Watershed: a stream and all the terrestrial
surface that drains into it
  • rich history of watershed scale studies in
    ecosystem ecology (“Small Watershed
    Approach” e.g. Bormann and Likens
    1967)
  • watershed studies use streams as
    ‘sampling device’, recording surface
    exports of water, nutrients, carbon,
    pollutants, etc., from the watershed;
    deforestation impacts on water supply to
    a city.
       Time Scales in Ecosystem
               Ecology
• Instantaneous: leaf-level
  photosynthesis and sunflecks
• Seasonal: deciduous forest, desert
  grassland
• Successional: 3 months after fire,
  300 years after fire
• Species migration/invasions: 1 to
  thousands of years
• Evolutionary history: Archaea and
  methane production
• Geologic history: glacial/interglacial
  cycles
      General Approaches
• Systems approach
  – Top-down
  – Based on observations of general patterns
• Mechanistic approach
  – Bottom-up
  – Based on process understanding
           Levels of Simplifying
              Assumptions
• Equilibrium - many early studies assumed some
  ecosystems were at equilibrium with their
  environment
   –   Closed systems dominated by internal recycling of materials
   –   Self-regulation and deterministic dynamics
   –   Stable endpoints or cycles
   –   Absence of disturbance and human influence
• Steady State – Balance between inputs and outputs
  to the system show no temporal trend (allows for
  spatial and temporal variation)
• Dynamic change – directional changes caused by
  humans?
      Ecosystem components
•   Plants
•   Decomposers
•   Animals
•   Abiotic components
    – Water
    – Atmosphere
    – Soil minerals
                     Feedbacks

• Negative feedbacks ( homeostatic) – when two
  components of a system have opposite effects on
  each other
   – i. predator – prey
   – ii. thermostat
• Positive feedbacks – when two components of a
  system have the same effect (positive or negative) on
  each other
   – runaway greenhouse effect – rising CO2 increases
       temperature, increasing respiration, increasing CO2
• Negative feedbacks are key to maintaining
  ecosystems in a given state, because they resist
  change
• Positive feedbacks, if unchecked, have the potential
  to shift ecosystems from one state to another
    Ecosystem processes: transfers of
    energy and materials from one pool
               to another
•   Can be transfers within the
    ecosystem, or, transfers between
    the ecosystem and its surroundings
    (e.g., atmosphere)
     –   Photosynthesis is a key ecosystem
         process, converting atmospheric
         CO2 to organic matter, and thereby
         providing the energy feeding the
         entire system
     –   Respiration – another key
         ecosystem process; oxidizes
         organic matter to CO2, consuming
         the energy provided by
         photosynthesis, and thereby returns
         CO2 to the atmosphere
     –   Other examples of ecosystem
         processes: Weathering,
         Evaporation, Nutrient uptake, Death
         & decomposition, Herbivory
   Controls over ecosystem processes: state factors,
          interactive controls, and feedbacks


                                            State factors
                                           set the boundary
                                           conditions – they
                                           are independent
                                            of ecosystem
                                               processes
 These effects
     (between                                 Interactive
   interactive                               controls both
  controls and                              affect and are
   ecosystem                                 affected by
   processes)                                 ecosystem
are mediated by                                processes
    feedbacks
  Why should we care about
    Ecosystem Ecology?

• Ecosystem ecology provides a mechanistic
  basis for understanding the Earth System
• Ecosystems provide goods and services to
  society
• Human activities are changing ecosystems
  (and therefore the Earth System)
            History of Ecosystem Ecology:
        contributions from various disciplines…
•    Tansley, British plant ecologist (1935) “The use
     and abuse of vegetational concepts and terms,”
     Ecology
•     First to coin term, ‘ecosystem’; emphasized
     interactions between biotic and abiotic; argued
     against exclusive focus on organisms
•     “The more fundamental conception is ... the whole
     system, including not only the organism complex,
     but also the whole complex of physical factors
     forming what we call the environment ... the habitat
     factors in the widest sense .... Our natural human
     prejudices force us to consider the organisms ... as
     the most important parts of these systems, but
     certainly the inorganic ‘factors’ are also parts, ...
     and there is constant interchange of the most
     various kinds within each system, not only between
     the organisms but between the organic and
     inorganic. These ecosystems, as we may call
     them, are of the most various kinds and sizes.”
    Frederick Frost Blackman (1866-1947), Plant physiologist (left)
    Sir Arthur George Tansley (1866-1947), Plant ecologist (right)
        History of Ecosystem Ecology:
    contributions from various disciplines…
• Vasily Vasilyevich Dokuchaiev
  (1846-1903)
• 1880s, led Russian soil scientists in
  developing a new scientific philosophy
  about soils and their relationship to
  climate, vegetation, parent material
  and time
• Dokuchaiev demonstrated that the
  most prevalent soils in any region of
  Russia, when broadly classified in
  terms of their most prominent soil
  profile characteristics, correlated well
  with climatic zones (zonal soils;
  intrazonal – influenced more by other
  factors and azonal - undeveloped)
       History of Ecosystem Ecology:
   contributions from various disciplines…
• Hans Jenny (1899-1992), soil
  scientist, “Factors of Soil
  Formation” (1941), and “The soil
  resource: origin and behavior”
  (1980)
• Formalized quantitatively
  Dokuchaiev’s factors of soil
  formation (S = f(clorpt))
• Many patterns of soil and
  ecosystem properties correlate
  with state factors
     - for example, very good correlation
     on the global scale between climate
     and ecosystem structure and
     processes
       History of Ecosystem Ecology:
   contributions from various disciplines…
• Raymond L. Lindeman (1915-1942),
  American limnologist, “The trophic-
  dynamic aspects of ecology” (1942) in
  journal Ecology
• Quantified pools and fluxes of energy
  in a lake ecosystem, emphasizing
  biotic and abiotic components and
  exchanges
• Fluxes of energy, critical ‘currency’ in
  ecosystem ecology, basis for
  comparison among ecosystems
• Synthesized with mathematical model
• Coupled energy flow with nutrient
  cycling
     History of Ecosystem Ecology:
 contributions from various disciplines…
• Lindeman’s model system at Cedar Bog Lake in
  Minnesota
          History of Ecosystem Ecology:
      contributions from various disciplines…
• J.D. Ovington, English forester (1962)
• Central question, how much water and
  nutrients are needed to produce a given
  amount of wood?
• Constructed ecosystem budgets of
  nutrients, water, and biomass (like
  Lindeman’s, but for forests)
• Also included inputs and outputs: exports
  of logs involves exports of nutrients, thus
  inputs of nutrients to forest required to
  maintain productivity
• One of the first to state the need for more
  basic understanding of ecosystem function
  for managing natural resources
History of Ecosystem Ecology:
contributions from various disciplines…
• Used radioactive tracers to study
  movement of energy and
  materials through a coral reef,
  documenting patterns of whole
  system metabolism

                                 Eugene P. Odum, 1913-2002


                • Systems analysis


               Howard T. Odum, 1924-2002
    Earth System and Global Change –
   Making History in Ecosystem Ecology
• Impact of human activities on
  Earth has led to the need to
  understand how ecosystem
  processes affect the atmosphere
  and oceans

• Large spatial scale, requiring new
  tools in Ecosystem Ecology
   – Eddy flux tower measurements of
     gas exchange over large regions
   – Remote sensing from satellites
   – Global networks of atmospheric
     sampling
   – Global models of ecosystem
     metabolism
       Earth System and Global Change –
      Making History in Ecosystem Ecology
Frontiers in Ecosystem Ecology,
integrating systems analysis,
process understanding, and global
scale
 – How do changes in the environment
   alter the controls over ecosystem
   processes?
 – What are the integrated system
   consequences of these changes?
 – How do these changes in ecosystem
   properties influence the earth system?
   Rapid human-induced changes
   occurring in ecosystems have blurred
   any previous distinction between basic
   research and management application.