1. Daily Science
Review Concept Check questions from Friday
In your HIP projects, what did your group find in the research of your topic that caused a disturbance in the environment? Was it with land, animals, other?
OR…can you describe the example with the keystone species article we read last week where natural disruptions were beneficial to that ecosystem?

2. Concept 54.3: Disturbance influences species diversity and composition
Decades ago, most ecologists favored the view that communities are in a state of equilibrium
Recent evidence of change has led to a nonequilibrium model, which describes communities as constantly changing after being buffeted by disturbances

3. Characterizing Disturbance
A disturbance is an event that changes a community, removes organisms from it, and alters resource availability
Fire is a significant disturbance in most terrestrial ecosystems
It is often a necessity in some communities
The large-scale fire in Yellowstone National Park in 1988 demonstrated that communities can often respond very rapidly to a massive disturbance

4. Plant species different from the former forest are recovering
Fig
Plant species different from the former forest are recovering
Figure Recovery following a large-scale disturbance
(a) Soon after fire
(b) One year after fire

5. Controlled Prairie Burn
Controls invasive species and is “controlled” in part due to the lack of vegetation in some areas, note the green grass vs. the tall weeds.

6. Early-arriving species and later-arriving species may be linked in one of three processes:
Early arrivals may facilitate appearance of later species by making the environment favorable
They may inhibit establishment of later species
They may tolerate later species but have no impact on their establishment

7. Ecological Succession
Ecological succession is the sequence of community and ecosystem changes after a disturbance
Primary succession occurs where no soil exists when succession begins
Secondary succession begins in an area where soil remains after a disturbance

8. Retreating glaciers provide a valuable field-research opportunity for observing succession
Succession on the moraines in Glacier Bay, Alaska, follows a predictable pattern of change in vegetation and soil characteristics

9. 1941 1907 Dryas stage Pioneer stage, with fireweed dominant 1860
Fig
1941
1907 2
Dryas stage 1
Pioneer stage, with
fireweed dominant 5 10 15
1860
Kilometers
Glacier
Bay
Figure Glacial retreat and primary succession at Glacier Bay, Alaska
Alaska
1760 4
Spruce stage 3
Alder stage

10. Succession is the result of changes induced by the vegetation itself
On the glacial moraines, vegetation lowers the soil pH and increases soil nitrogen content

11. 60 50 40 Soil nitrogen (g/m2) 30 20 10 Pioneer Dryas Alder Spruce
Fig 60 50 40
Soil nitrogen (g/m2) 30 20
Figure Changes in soil nitrogen content during succession at Glacier Bay 10
Pioneer
Dryas
Alder
Spruce
Successional stage