Ecosystem structure and function
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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

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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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