1. 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

2. HOW DO WE STUDY AND DEFINE ECOSYSTEM STRUCTURE? – I +Much of ecosystem structure can be inferred from vegetation structure: Plants  Consumers (fauna)  Decomposer fauna and flora  Soil structure (Ricklefs)

3. HOW DO WE STUDY AND DEFINE ECOSYSTEM STRUCTURE? – II +Vegetation structure defined by dominant plants: – By dominance and density of trees, shrubs, grasses –  Forest  woodland  savanna  grassland  Shrubland  shrubsteppe  grassland SAVANNAGRASSLAND (profiles from Walter, 1985)

4. HOW DO WE STUDY AND DEFINE ECOSYSTEM STRUCTURE? – III +Functional aspects of vegetation in definition Leaf duration – Evergreen, winter or drought deciduous Leaf shape/size – Broadleaf, needleleaf Photosynthetic pathway: for Grasses (C3, C4) Tropical Savanna with Drought-Deciduous Trees and C4 Grasses Tropical Rain Forest with Broadleaf Rain-Evergreen Trees (profile/photo from Walter, 1985)

5. WHY IMPORTANT? – ROLE OF VEGETATION STRUCTURE IN THE EARTH SYSTEM – I +FUNCTION FOLLOWS STRUCTURE: Biophysical processes vary with vegetation type ATMOSPHERE-BIOSPHERE EXCHANGE   MATTER – H 2 O (Transpiration)  ENERGY – SOLAR ABSORPTION, HEATING REGIONAL AND GLOBAL CLIMATE (Mackenzie 1998)

6. 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

7. WHY IMPORTANT? – ROLE OF VEGETATION STRUCTURE IN THE EARTH SYSTEM – III Vegetation structure affects wildlife habitat  Food, shelter  Vegetation complexity  Habitat complexity Vegetation and human society –  Managed vs. unmanaged uses  Shelter – Wood, fiber  Food – Grazing, crops, secondary forest products  Watershed management  Aesthetic, cultural values

8. WHAT FACTORS CONTROL VEGETATION DISTRIBUTION? – I FIVE KEY FACTORS: +REGIONAL CLIMATE – 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.)

9. WHAT FACTORS CONTROL VEGETATION DISTRIBUTION? – II FIVE KEY FACTORS (con’t): +REGIONAL CLIMATE – Broad patterns of: Physical Climate  Seasonal thermal, moisture, and light regime  Climate variability and directional change Chemical Climate  Atmospheric CO 2 concentration – fertilization effect  Acid rain  N deposition – fertilization effect

10. 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)

11. DRIVERS OF FUTURE ECOLOGICAL CHANGE: MULTIPLE FACTORS +Climate change – Anthropogenic forcings: Greenhouse gas emissions (GHG): CO 2, CH 4, etc Sulfate aerosols (SUL), Cloud condensation nuclei,.. Landuse change  Surface biophysical properties +Disturbance – Landuse change: Deforestation, cropland conversion Overgrazing, desertification Species invasions +Fertilization effects: CO 2 N deposition