Activity 6: For You To Do
Teaching Suggestions and Sample Answers

3. a) and b) The number of kinds of plants increased as the years passed. In the inland areas, three years after the eruption, from a bare ground, 2 kinds of plants appeared – grasses and ferns. After 13 years, the ferns disappeared and 3 kinds of plants dominated – grasses, orchids and horsetail trees. After 23 years, the grasses, orchids and horsetail trees now shared the island with coconut trees, making a total of 4 kinds of plants. After 47 years, the kinds of plants remained the same and only the numbers increased.

c) Yes. In the inland areas, in 10 years – from the 3rd year to the 13th year while the number of grasses increased, the ferns disappeared and orchids and horsetail trees appeared. Along the coastal areas, while the grasses, ferns and many tropical seashore plants disappeared; young coconut trees horsetail trees and sugar cane plants completely covered the area.

d) The plants came from neighboring islands. Plants propagate through very efficient seed dispersal. One way of seed dispersal is the use of wind for the spread of the plant seeds. Another way that is useful on this island, is the water dispersal of seeds.

e) Almost five decades was needed for the complete recovery of the forest growth.

f) It takes decades for a forest to recover from a volcanic eruption. Plants that appear initially may either increase their numbers or totally disappear. Shorter plants are replaced by taller trees.

g) Although the “rebirth” of plant life on the coastal areas is parallel to that in the inland areas, change occurred faster on the coastal areas. Comparing the two areas shows that change on the coastal area was a step ahead of the inland area. It took 13 years after the eruption, for the inland areas to be completely covered with young coconut trees, horsetail trees, and sugar-cane plants and 23 years for the inland areas to go through the same process. It appears that the coastal area’s recovery happened sooner than that of the inland area.

The coastal areas with their proximity to a large body of water had their temperature go down sooner than those in the inland areas. With the lower temperature and the presence of wind and water dispersed seeds, plants appeared sooner on the coastal areas compared with those in the inland areas.