1. Questions of the day 1. How are forests vital for humans?
2. Why are forests important to PA?

2. Succession: Changing Ecosystems
Ecological Succession:
Pond to Forest
Harvested/Disturbed Forest
to Old-growth Forest

3. Ecological Succession
Why do some organisms flourish and others disappear?
Conditions of the environment change and may become unsuitable for some species
The series of changes in which the original species are replaced by new species
Natural “aging” of an ecosystem
Rate: depends on climate, impacted by human activity

4. Pond to Forest Pioneer stage- muddy sandy bottom
Submerged plant stage-occurs due to humus that has accumulated
Emerging plant stage-cattails, bulrushes at edge of pond

5. Pond to Forest-cont’d
Marsh-shallow water with grasses and other rooted plants
Swamp-organic matter built up, tree species, (red cedar, red maple) seasonally wet
Beech-maple forest-climax community

6. Ecological Succession-Washington State’s Olympic Peninsula
Forests- disturbed by fires, landslide, clear cutting, etc.
Regeneration through succession
Time frame: decades to centuries
Field trip-Pacific Northwest, coastal area elevation 180 meters, visit over 300 year development

7. Site 1

8. Field trip: Site 1
Describe how the forest ecosystem has been disturbed.
What was the fate of the ecosystem’s organisms and what might happen to the soil?
If no human intervention, what will this site look like in 15 years?

9. Site 2 Young Red Adler Red Adler Young Douglas Fir
Nitrogen-fixing root nodules

10. Site 2 Characteristics:
Red alder-restore nitrogen back to the soil, with the nitrogen-fixing bacteria in nodules on the roots
Grasses
Young firs-need N
Deer, grazing species, field mice

11. Site 3 Douglas Fir Broadleaf Maple Young Douglas Fir Young Red Cedar
Young Western Hemlock
Sword Ferns

12. Site 3: 60-75 years later, no human intervention
What do you notice?
What new tree species are present?
What happen to the previous tree species?
What does that tell you about the pioneer species?

13. Site 4 Western Red Cedar Western Hemlock Young Western Hemlock
Sword Ferns

14. Site 4: 270-300 years, no H.I. What are the dominate tree species?
What are the shade-tolerant species?
What would the condition of the soil be?
Climax stage of succession: forest is mature, ecologically stable
Will it stay this way? What disturbances can bring it back to site 1?

15. Review Questions from yesterday’s activity