1. Signs of Forest Succession in Maine
Prepared for Maine EcoScienceWorks,
August 2006
All images by Robert Bryan except as noted. All images except those by others may be reproduced for educational purposes with the following credit: Photo by Robert Bryan, Maine Audubon
Use “normal” view to see detailed notes

2. Note to teachers:
This slide show is designed to introduce some of the concepts of “Field to Forest” and “Forest to Forest” succession that commonly occurs in Maine. This presentation is designed to be reviewed before conducting the EcoScienceWorks succession field exercise. It would be a good general introduction to succession and could be reviewed with students before doing the EcoBeaker Beaver Pond Succession lab.
This presentation could be used as a self study module for students, or it can be presented to the entire class. In the latter case, depending on your teaching style, you might want to delete some of the text boxes, since they say much of what you might say in class.
Note to students and teachers:
First, view the presentation in “slide show” view because some of the slides have layered effects that are only available in that view. If you come to a question, look at the slide and try to answer the question before clicking for the answer.
Then view the presentation in “normal” view to see the notes at the bottom. These notes have more detail than the brief text boxes on the slides.

3. Have you seen something like this? What happened here?
Field to forest succession. Who has seen this when walking in the woods? Four million acres in Maine (an area almost the size of New Hampshire) that was once farmland is now forest.
This was once a pasture with no trees. 4 million acres in Maine like this have undergone “field to forest” succession.
This slide show will help you become a forest detective by teaching you common “signs of succession” that you can find in most woodlots.

4. 1855
1830
Succession after farm abandonment. Much of southern and central Maine looked like this at different times over the last 150 years. These scenes are from central Massachusetts. The peak of farming was a little later in Maine, probably around the time of the Civil War.
2000
1910
Farm to Forest Succession – Harvard Forest Dioramas (source:

5. Note the open landscape Your town’s historical society will probably have photos like this.
Bowdoin, ME (undated)
Source:

6. Old Farmhouse Foundation, Acton, Maine, 2005.
Trees in old farmhouse foundation, Acton, ME
Old Farmhouse Foundation, Acton, Maine, 2005.

7. 3 Stages of Succession, Falmouth, ME Field
Young Forest
Shrub
3 stages of succession: field, old field with red-osier dogwood and alder (species you will meet in the Ecobeaker computer lab) and young hardwood forest.
3 Stages of Succession, Falmouth, ME
Field

8. Early succession, old field 10 years after last mowing
White Pine Seed Source
White Pine
Common Juniper
Red Oak
Early succession, old field 10 years after last mowing

9. This tree grew up in an open pasture (note the wide, spreading crown and low branches). Sheep once sought shade under this tree. Now it is surrounded by young deciduous forest. Foresters call these old field trees “wolf trees.”
Yellow Birch “Wolf Tree.” Wide spreading branches show that this tree grew in the open before the small trees were growing. Nobleboro, ME

10. Early succession aspen-birch forest. Note the stumps
Early succession aspen-birch forest. Note the stumps. Logging and other forms of disturbance “set back the clock” of succession.
Early succession, aspen (popple) and birch after heavy logging disturbance, Bangor, ME

11. Each succession stage has its characteristic wildlife species
Each succession stage has its characteristic wildlife species. Moose like early-succession deciduous forest that provides abundant browse.
Different species of wildlife prefer different stages of succession. Moose thrive in young forests, which have broad-leaved plants within easy reach.

12. Forest structure is a key “sign of succession
Forest structure is a key “sign of succession.” This is an aspen forest in Colorado that probably became established after a forest fire. (Aspens sprout from roots after the tree is cut or killed by fire). Note that the trees are all about the same size and there is no understory growth. For a forest, this is still early succession. The dense canopy shades out new trees and shrubs. As forests get taller and older and trees begin to die, gaps in the canopy allow light to reach the forest floor and new trees will begin to grow.
The dense canopy of young forests shades out most understory plants. A single canopy layer of small to medium-sized trees is also characteristic of young forests. Aspen (“popple”) forest, Colorado.

13. Young aspen forest in Maine. Note the conifers in the understory
Young aspen forest in Maine. Note the conifers in the understory. Succession is occurring - evnetually the aspens will die (they only live about 100 years) and the conifers and long-lived deciduous trees will take over the site.
Early succession stages have sun loving plants like these aspens and birches, but these trees usually have short life span for a tree (about 100 years). Trees and other plants that can tolerate shade grow in the understory and eventually dominate the site when the other trees die. Note the understory conifers that will eventually reach the overstory through succession.

14. Here is a similar site a later stage in succession
Here is a similar site a later stage in succession. Hemlock, a long-lived shade-tolerant conifer is replacing the sun-loving aspen, birch, and red maple.

15. White pine is a common “old field” tree species in New England
White pine is a common “old field” tree species in New England. These trees are all about the same height, and there is little understory. These trees are perhaps years od. This is still the first phase of forest succession. Note the stick nest in the middle tree. Goshawks are fearless predators that hunt birds in flight by flying beneath the forest canopy. They nest in areas of extensive forests and will attack humans that get too near the nest when they have young.
White pine is a common “old field” tree species in New England. Recall the earlier slide with white pine seedlings in a field. Note forest structure. What stage does this suggest?

16. This is a red spruce forest on Cranberry Island off Friendship Maine
This is a red spruce forest on Cranberry Island off Friendship Maine. Like most Maine islands, Cranberry was cleared for pasture in he 1800’s. (See if you can find a “Hog,” “Sheep,” or “”Cow” Island on a map!. This forest may be over 80 years old, but it still has a “young” forest structure. Note the dense canopy, medium diameter of trees, and lack of understory and downed logs. Red spruce can live for over 250 years. Spruce-fir forests are found in cool moist habitats, including coastal islands and peninsulas, mountains, and in the deep woods of northern and Down East Maine.
Island spruce, Muscongus Bay, ME. Although more than 80 years old this forest still has a “young” structure.

17. Late succession stages have plenty of dead trees like this old growth spruce-fir forest in Colorado.
Late-succession spruce-fir forest in southern Colorado. Note the abundance of downed logs.
Some times the oldest stage of succession is called a “climax forest” because it can last a long time and regenerate itself after disturbances.

18. Dead and dying trees and logs have many ecological values.
Many species of insects, fungi, birds, and mammals live only in dead and dying trees and many depend of them to find food.
Porcupine den tree, Hinckley, ME, 2006.

19. Older hemlock-spruce forest in Beddington, ME at Pleasant River Lake State Park. If there were more big trees over 40 cm (16 inched) diameter and more understory development we might call this a “late-successional” forest. Hemlock reproduces well in small gaps (it is “shade-tolerant”) so in the absence of major disturbance it can form a stable long-lived community called a “climax” community.
Hermit thrush nest. Hermit thrushes nest under ground cover vegetation in mature forests.
Hemlock forest, Pleasant River State Park, Beddington, ME. What signs of succession do you see?

20. Hermit thrushes prefer to nest in older forests with dense ground cover. Hermit thrushes are related to robins, which also have blue eggs but nest in small trees and shrubs.

21. Shade-tolerant plants
Late Succession
Early Succession
Sun-loving plants
Shade-tolerant plants
0 years
0-10
10-30
30-80
125+ years
Young, simple forest
Old, complex forest
Mown Field
Old Field
Sapling-shrub
This is a general timeline for field to forest succession and forest to forest succession (caused by disturbance) in the northeast.
Disturbance

22. Forest disturbance allows light to reach the forest floor and new plants to grow. “Pillow and cradle” topography created by fallen trees is characteristic of areas that were never plowed.
Wind belw down these trees. This created a gap in this hemlock forest that will enable seedlings to become established.
Over time the wood will rot and the soil will form a “hummock and hollow” or “cradle and pillow” pattern suggested by the red line. This pattern can be seen in many woodlands. An area that was a plowed field will usually be very smooth on the surface, but and area that was pasture will have a hummock and hollow pattern. Seedlings will often become established on the pile of soils that forms the “hummock.”

23. Can you see what happened here?
This is an area with older pillows and cradles, created when trees fell in a hurricane about 50 years ago. Hog Island, Muscongus Bay, Maine, 2006.

24. What killed these trees?
This wet meadow in Orono, ME was once a forest that was flooded by beavers.
Beavers cause intermediate-sized disturbances. Note the trees from the forest that stood here before the beavers flooded this area. Now the beavers have left and grasses and sedges (which have edges!) are growing where there was once several feet of water. Over time the process of succession will continue, with shrubs and then trees taking over the site.

25. What Happened here?
Wind blew down the trees in middle. The older, sun-loving white spruce in the canopy only lives for 100 years. It is being replaced by shade-tolerant red spruce that can live for more than 300 years. Hog Island, Muscongus Bay, ME, 2006.

26. Insects are another form of disturbance that can “set back the clock” of succession. The mature trees in this Colorado lodgepole pine forest were killed by pine beetle. You can see the process of succession starting again. Over time the young pines on that you see will grow into a mature forest.
Insects are another form of disturbance that will set back the clock of succession. Here, the mature forest canopy is being replaced by younger trees. Lodgepole pine, Colorado. Name other types of forest disturbance.

27. Succession and Disturbance: forests: are always changing…
Much of this area at South Branch Pond in Baxter State Park was heavily logged and burned before it became a park.
Succession and Disturbance: forests: are always changing…