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ECOSYSTEM STRUCTURE AND FUNCTION. How do we define ecosystem structure Importance of ecosystem structure Factors controlling ecosystem structure Drivers of future ecological change. ©2001 T. Kittel, NCAR . HOW DO WE STUDY AND DEFINE ECOSYSTEM STRUCTURE? – I.

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ecosystem structure and function
ECOSYSTEM STRUCTURE AND FUNCTION
  • How do we define ecosystem structure
  • Importance of ecosystem structure
  • Factors controlling ecosystem structure
  • Drivers of future ecological change

©2001 T. Kittel, NCAR

how do we study and define ecosystem structure i
HOW DO WE STUDY AND DEFINEECOSYSTEM STRUCTURE? – I
  • Much of ecosystem structure can be inferred from vegetation structure:

Plants  Consumers (fauna)

 Decomposer fauna and flora

 Soil structure

(Ricklefs)

how do we study and define ecosystem structure ii
HOW DO WE STUDY AND DEFINEECOSYSTEM STRUCTURE? – II
  • Vegetation structure defined by dominant plants:

– By dominance and density of trees, shrubs, grasses –

      • Forest  woodland  savanna  grassland
      • Shrubland  shrubsteppe  grassland

SAVANNA

GRASSLAND

(profiles from Walter, 1985)

how do we study and define ecosystem structure iii

Tropical Rain Forest with Broadleaf Rain-Evergreen Trees

Tropical Savanna with Drought-Deciduous Trees and C4 Grasses

HOW DO WE STUDY AND DEFINEECOSYSTEM STRUCTURE? – III
  • Functional aspects of vegetation in definition
    • Leafduration – Evergreen, winter or drought deciduous
    • Leafshape/size – Broadleaf, needleleaf
    • Photosyntheticpathway: for Grasses (C3, C4)

(profile/photo from Walter, 1985)

why important role of vegetation structure in the earth system i
WHY IMPORTANT? – ROLE OF VEGETATION STRUCTURE IN THE EARTH SYSTEM – I
  • FUNCTION FOLLOWS STRUCTURE:
    • Biophysicalprocesses vary with vegetation type

ATMOSPHERE-BIOSPHERE EXCHANGE 

      • MATTER – H2O (Transpiration)
      • ENERGY – SOLAR ABSORPTION, HEATING

REGIONAL AND GLOBAL CLIMATE

(Mackenzie 1998)

why important role of vegetation structure in the earth system ii
WHY IMPORTANT? – ROLE OF VEGETATION STRUCTURE IN THE EARTH SYSTEM – II
  • Vegetation type affects biogeochemical processes

e.g., Global C and N Cycles

    • NET PRIMARY PRODUCTION – C assimilation, N uptake
    • PLANT C, N INPUTS TO SOIL  DECOMPOSITION RATES

TERRESTRIAL C, N FLUXES TO THE ATMOSPHERE

        • RADIATIVELY-ACTIVE TRACE GASES

GLOBAL CLIMATE

why important role of vegetation structure in the earth system iii
WHY IMPORTANT? – ROLE OF VEGETATION STRUCTURE IN THE EARTH SYSTEM – III
  • Vegetation structure affects wildlifehabitat
    • Food, shelter
    • Vegetation complexity  Habitat complexity
  • Vegetation and human society –
    • Managed vs. unmanaged uses
    • Shelter – Wood, fiber
    • Food – Grazing, crops, secondary forest products
    • Watershedmanagement
    • Aesthetic, cultural values
what factors control vegetation distribution i
WHAT FACTORS CONTROL VEGETATION DISTRIBUTION? – I

FIVE KEY FACTORS:

  • REGIONALCLIMATE – Broad patterns
  • TOPOGRAPHY – Slope, aspect, exposure
  • BEDROCK – Soil parent material, soil genesis
  • BIOTA – Competition, herbivory,

biotic disturbance (insect outbreaks, human)

  • TIME – Succession, disturbance (fire, etc.)
what factors control vegetation distribution ii
WHAT FACTORS CONTROL VEGETATION DISTRIBUTION? – II

FIVE KEY FACTORS (con’t):

  • REGIONALCLIMATE – Broad patterns of:
    • Physical Climate
      • Seasonalthermal, moisture, and light regime
      • Climatevariability and directional change
    • Chemical Climate
      • Atmospheric CO2 concentration – fertilization effect
      • Acid rain
      • N deposition – fertilization effect
what factors control vegetation distribution iii
WHAT FACTORS CONTROL VEGETATION DISTRIBUTION? – III

Scale determines relative importance of controls:

  • GLOBAL/CONTINENTAL – Broad patterns of climate determines biome to ecoregional vegetation
  • LANDSCAPE/LOCAL – Microclimate, geomorphology, soils, time, grazers, human activity

e.g., Conifer forests, Colorado Front Range

(Walter 1985)

(Neilson et al. 1998)

drivers of future ecological change multiple factors
DRIVERS OF FUTURE ECOLOGICAL CHANGE: MULTIPLE FACTORS
  • Climatechange – Anthropogenic forcings:
    • Greenhouse gas emissions (GHG): CO2, CH4, etc
    • Sulfate aerosols (SUL), Cloud condensation nuclei, ..
    • Landuse change  Surface biophysical properties
  • Disturbance – Landuse change:
    • Deforestation, cropland conversion
    • Overgrazing, desertification
    • Species invasions
  • Fertilizationeffects:
    • CO2
    • N deposition
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