Page 39 - Science Course 3 (Book 1)

Mo1-L4a: How Do Land Ecosystems Change?

In areas where existing ecosystems have been disturbed or destroyed, secondary succession can occur.

Secondary Succession

Pioneer Species Intermediate Climax
Species Community

Grasses and Grasses, shrubs, Mature oak and
Fire Annual plants perennials pines, young oak hickory forest
and hickory
0 years 1-2 years 3-4 years 5-150 years 150+ years

Settlers in New England cleared many acres of forest Seeds of grasses, wildflowers, and other plants
to create cropland. In places where people stopped quickly began to sprout and grow. Young shrubs and
planting crops, the forest began to grow back trees also started growing. These plants provided
habitats for insects and other small animals, such as
mice.

White pines and poplars were the first trees in the Eventually, a climax community of beech and maple
area to grow to their full height. They provided shade trees developed. As older trees die, new beech and
and protection to slower growing trees, such as maple seedlings grow and replace them.
beech and maple.

SUMMARY

How Do Land Ecosystems Change?
Ecosystems change in predictable ways The final stage of ecological succession in a
through ecological succession. land ecosystem is a climax community

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