Terrestrial Ecosystems

Ecosystem:

• A community of organisms and their physical environment

• Consists of biotic and abiotic elements

Biotic Elements of Ecosystems

• organisms: individuals of various specie

• biomass: all of the living and non-living biological material

• genetic resources: indicates total variation among populations of species in a community

Abiotic Elements of Ecosystems

• Air: gas exchange

• Water: photosynthesis

• Sunlight: photosynthesis

• Temperature: warmth for metabolic activity

• Nutrients: photosynthesis in plants; energy in animals and CO₂ is a major plant nutrients

• The list above constitue the potentially limiting factors to plant growth in an ecosystem

Photosynthesis

• 6CO₂ + 6H₂O —SUNLIGHT—> C₆H₁₂O₆ + 6O₂

• Carbon Dioxide + Water —> Carbohydrates + Oxygen

Biome

• a collection of broadly similar types of plants and animals in a geographical area

• Primarily a function of climate, which determines what kind of organisms can live there

Plant Growth Form

• Size/woodiness/lifespan

  • herb

  • annual

  • herbaceous perennial

  • woody perennial

  • tree

  • vine

• Degree of independence

  • green and rooted in the ground

  • parasitic

  • saprophytic

  • epiphytic

• Leaf traits

  • large or small

  • sclerophyllous

  • simple or compound

  • evergreen

  • winter deciduous

  • drought deciduous

  • needleleaf or broadleaf

Four Main Biome Types:

1. Forest

   • associations of large woody perennial tree species

   • height of trees generally allows them to form a closed canopy

   • exist only where there is a net moisture balance

2. Grassland

3. Desert

4. Artic and Alpine Tundra

Forest Ecosystems

• Tropical forests:

  • tropical rainforests

  • monsoon rainforest

  • thornbush and scrub forest

• Midlatitude forests:

  • Mediterranean sclerophyllous woodland

  • broadleaf deciduous forest

  • broadleaf evergreen forest

  • mixed forest

  • coniferous forest

Grassland Ecosystems

• Extensive in continental interiors with most precipitation in summer

• Grasses dominate where trees/shrubs can't tolerate soil moisture extremes

• Grasslands have expanded into forested areas due to human agriculture

Xerophytic Adaptations of Plants

• How plants cope with drought conditions:

  • deep roots (where there is deep soil moisture or groundwater: phreatophytes

  • small leaves

  • waxy coating on leaves

  • deciduous (winter or dry season)

  • rapid germination and flowering; annuals

  • water storage (succulence)

  • hairs or spines

  • shallow roots (when deep water does not exist)

  • CAM and C4 metabolic pathways

CAM and C4 metabolic pathways

• CAM:

  • 20,000 species in 40 families; 8% of all land plants

  • Examples:

    • bromeliads

    • agaves

    • cacti

    • many epiphytes ad succulents

• C4

  • adaptations to high temperature environments; more efficient use of water

  • 3% of all land plant species

  • 5% of all land plant biomass

  • 23% of terrestrial carbon fixation

  • Mostly grasses and sedges