Lab 12: Population Structure of a Forest

1
Lab 12 Population Structure of a Forest
2
Community Structure

• To understand dynamics of a community
• Succession
• Dominance
• Indicate community's position in the sere

3
Sandhill Association

• Overstory longleaf pine turkey oak
• Shrub layer rusty lyonia, saw palmetto
• Ground cover wiregrass
• Fire climax community
• Fire absent since 1963
• Sand pine dominates over longleaf in absence of
  fire.

4
Questions

• What species dominates the tree layer?
• Is secondary succession occurring?
• Succession is controlled by influences of one
  species on the autecology of another.
• LLP, SP, oaks
• Is dominance shifting?

5
Dominance

• Dominance ability to utilize more nutrients in a
  forest than another species
• Organize species by dominance level
• Dominant species indicates successional stage of
  the community.

6
Dominance Measures

• frequency plots w/ sp. X / total plots
• Is frequency a reliable indicator of dominance?
• Does not take into account of individuals or
  their size.
• Only relates the presence of species from
  different community types.

7
Dominance Measures

• Density individuals / unit area
• Is density a reliable indicator of dominance?
• Seedlings can inflate the measurement due to
  over-representation in their first years due to
  low levels of competition.
• 1 adult tree many small in terms of nutrient
  utilization

8
Dominance Measures

• Basal Area p r2 p (d/2)2
• Measure of the area a tree utilizes for nutrient.
• Proportional to the spread of a trees crown
• Drip line lateral extent of root system
• Competition among trees depends partially on
  crown size
• DBH
• Mirror periscope

9
DBH

• Diameter breast height
• Specially calibrated tape measure that measures
  diameter while wrapped around the circumference
  of a tree
• Breast height???
• 1.37 m or 4.5 ft