In New England, many of our ecosystems are recovering from past disturbances, such as clearing for agriculture. When economic conditions caused farms to move westward, land was left fallow, allowing nature to take over again.
Vegetation unfolds in a predictable pattern on abandoned land. First, it is colonized by a variety of weeds. Later, invading shrubs and seedlings, such as red maple, tend to dominate. Under the shade of these trees, long-lived species, such as sugar maple and oaks, gradually replace the early arrivals.
Ecologists have a number of theories about what controls this pattern of succession. Sometimes the early arrivals change the environment in a way that makes it more suitable for later colonists, such as by improving the quality of the soil.
Early arrivals often have wind-blown seeds that disperse rapidly over large areas, whereas long-lived, late establishers, such as many oaks, have heavy acorns that disperse more slowly. The last species to establish are often tolerant of deep shade, which means they can reproduce under the canopy provided by early arrivals.
Understanding succession has practical aspects. Electric utilities are interested in thwarting succession under power lines, to reduce the need to spray herbicides or to cut back vegetation. Foresters like to speed up succession, so desirable hardwoods establish faster on harvested lands.
And wildlife managers need to maintain shrubby ‘early succession’ habitat to ensure the survival of a variety of wildlife, including American woodcock, bobcat, and the New England cottontail.
Photo, taken on November 25, 2008 using a Pentax Optio 750Z, courtesy Matthew Rutledge via Flickr.