Secondary Succession Lab




For this lab you will determine the tree species in three separate plots, with the aide of your instructor.  Each plot will be farther back in the forest than the one before it. You will notice that the farther back into the forest you go the older the forest becomes. To better understand this lab, let’s look at what Secondary Succession is.

Secondary Succession begins in habitats where communities were entirely or partially destroyed by some kind of damaging events. For example, secondary succession occurs in habitats damaged by fire, floods, insects, overgrazing, or forest clear-cutting, and in disturbed areas such as abandoned agricultural fields or vacant lots. Because these habitats previously supported communities, soil and seeds are often already present. For example secondary succession on abandoned cropland (old-field succession) typically begins with the germination of r-selected species from seeds already in the soil (grasses, weeds, etc.). The trees that ultimately follow are region specific.  In some regions of the eastern US, pines take root next, followed by various hardwoods (oak, hickory, dogwood, etc.), as you will begin to see in this lab.

Our three plot examples will be constructed on an old field. After this field was abandoned, the site was colonized by weedy short-lived herbaceous species such as crab grass, the seed of which may have already been present in the soil. After a year or so the site was dominated by perennial herbaceous species such as goldenrod and dog fennel. These species have out competed the earlier colonists and replaced them. They produced many small seeds that were wind dispersed and could travel long distances. Later, woody species such as blackberries and sumac invaded. Birds and small mammals often dispersed the seed of these species. As they grew, they began to dominate and crowd out the goldenrods and dog fennels. Then early successional tree species such as loblolly pines invaded. Finally after the canopy of the pines closed, in fifteen to twenty years the sumacs, blackberries and young pines can no longer survive in the shady conditions. Then young shade tolerant species invaded and eventually replaced the pines. Finally the climax species for that site become established and dominate until another disturbance occurs.

Below is a list of tree species based on their tolerance to shade. You will need to include this information in your lab report.  The species requiring full sunlight for growth will only become established in the early stages of succession. Eventually as light levels on the forest floor decrease, they will be replaced by more and more shade tolerant species until the most shade tolerant or climax species dominate.


Very Tolerant
Tolerant
Intermediate
Intolerant
Very Intolerant
Hop hornbeam

Hornbeam

Beech

American Holly

Sugar Maple

Flowering Dogwood

Southern Magnolia

Spruce Pine

Virginia Bay Magnolia

Atlantic White Cedar

Poison Sumac

 Red Maple

Basswood

Persimmon

White oak

Elm

Shumard Oak

Sourwood

Carolina Laurel Cherry

Swamp Chestnut Oak

 Red oak

Hickory

Hackberry

Ash

Water oak

Upland laurel oak

 Yellow poplar

Sycamore

Sweetgum

Sassafras

Blackgum

Black Cherry

Red cedar

Short leaf pine

Loblolly pine

Mimosa

Pear

Southern Crab-apple

 Longleaf pine

Willows

Cottonwoods

Black locust

Bald Cypress

Alder
 

In this lab you will also calculate two diversity indexes for each of the three plots:

Discuss tree species diversity in relation to succession in your lab report.


Links:
Succession
Secondary Succession
Old-field Succession Photo Gallery
OLD FIELD SUCCESSION