Ecology

The Acadian forest has a role for every tree – young and old, living and dead

The Acadian forest is home to 32 native tree species. The Acadian forest is made up of all different ages of trees. Each tree, of each age, plays an important role in keeping the forest healthy and all systems working properly. Within each mature forest there are typically mature trees, dead and dying trees, and seedlings and saplings.

Dead and dying trees provide nesting sites and homes for hundreds of species of wildlife. Woodpeckers are able to drill holes in trees that become softer with age and decay. These woodpecker-made holes are called tree cavities. Birds and mammals often nest in tree cavities that are made in the older trees, or dead trees called snags.

When these dead trees fall down, they create habitat for many species, like insects and salamanders. Many forest insects feed on the dead wood and by digesting the dead wood, turn it into new soil. Salamanders in turn feed on these insects. The dead wood on the ground is also called coarse woody debris. Coarse woody debris provides the perfect nursery for seedlings. The coarse woody debris provides nutrients, soft material in which to establish roots and often lift the seedlings up off the ground to provide a little extra light and freedom from competition of other established plants.

Seedlings and saplings are young trees in the forest that provide the new generation of trees for our future forest. Most seedlings never grow up to become trees, they are eaten by forest wildlife, or fail to get enough light to grow, or are killed by disease. Many trees are damaged or killed at the sapling stages as well. The seedlings and saplings that do survive are the healthy and strong trees, well suited to meet the demands of their environment. These are the trees that make up our forest.

Mature trees dominate the forest canopy and provide the seed that produce forest seedlings. Mature trees produce seed and transfer genes to the next generation of seedlings. This process continues until the tree grows old and dies – providing more snags and coarse woody debris, and eventually making up the soil that will support the future generation of trees.

How old is the Acadian forest?

The Acadian forest began developing over 10,000 years ago when the glaciers began moving North after the last ice age. After the ice left the Maritimes, species slowly began moving northward. Species that were adapted to colder conditions would have been the first to migrate into the Maritime Provinces, including spruce, white birch and poplar. Then as the temperatures began warming, southern species would have migrated northward as well. Because today’s climate still has a cold winter, but warm springs in summers, our forest remains a diverse mix of both northern and southern species.

Acadian forest has the ability to grow to be a very old forest. Tree species such as sugar maple, ash, cedar and yellow birch can reach ages of over 200 years. Red spruce and white pine can grow to be 400 years old. Eastern hemlock is our oldest living species, sometimes living to the age of 800 years.

Most of these these species can grow up under the canopy of older, established trees, not requiring very much sunlight. These species are otherwise known as shade tolerant species – because they have the ability to tolerate shade. Young trees take advantage of small gaps in the canopy that open up when older and larger individual or small groups of trees die, or blow down. This causes the many layers of trees you can see in the Acadian forest – with seedlings, saplings, mature trees and dead wood all existing in the same stand. All of these trees play an important role in keeping our Acadian forest healthy.

What are some of the ecologically important features of New Brunswick’s public forest?

The headwaters of the Miramichi, Restigouche, Upsalquitch, Nepisiguit, and St. Croix Rivers have their source on Crown Lands and flow almost entirely through our public forests.

Crown lands are home to 32 species of native trees and 30,000 species of wildlife. The Canada lynx is currently listed as endangered. At least 40 species of forest plants are provincially listed as May be at Risk. The grey wolf was extirpated from NB in 1921 due to overhunting. The woodlands caribou was extirpated from NB in the 1930s. Wolverine and timberwolf are other species that  have been extirpated from New Brunswick.

Biodiversity provides ecosystem stability

The common analogy is the airplane story. How many rivets can you remove from an airplane before the airplane falls apart? How many species and structures of the forest can you remove and still have the forest function properly? Many species rely on both hardwood and softwood species for their habitat needs.

Here are some examples…

Northern Flying Squirrels can glide up to 40 feet between trees, using their specially flattened tails as a directional rudder. Northern Flying Squirrels will typically choose softwood trees for their landings, because the softwood’s thick bark is easier to grab and hold. When fueling up for their gliding sessions flying squirrels feed on truffles (mushrooms) that grow around the roots of softwood and hardwood trees. As the squirrels move throughout the forest, they release the mushroom spores in their pellets.

The spores eventually meet with a hardwood tree root and develop an important relationship with the roots. The roots provide water and nutrients to the fungus as it grows. As the fungus grows it is able to reach even further into the soil than the trees own root system and provides the tree with even more water and nutrients than the tree could acquire on its own. This is one way the animals and plants of the Acadian forest work together to increase forest productivity!

The Blackburnian Warbler likes to nest at the very tops of spruce and hemlock trees. When it comes to feeding, they prefer stands with lots of leaves that are high in the canopy. Mixed wood stands (which have a mixture of softwood and hardwood trees) provide the right conditions for the trees to grow very tall. In these stands, the leaves in the canopy can grow very high providing the perfect conditions for the Blackburnian Warbler.

Blackburnian Warblers along with dozens of other species of migratory forest birds, fly all the way from South America to the Acadian forest every spring. Why? In order to take advantage of the incredible explosion of insects that takes place every spring in the Acadian forest. The insects are so abundant in New Brunswick in the spring and summer, that tropical birds move from their wintering grounds in the rainforests, to the Northern forests in order to raise their young. The Blackburnian warbler and dozens of other bird species play a key role in keeping insect populations under control in our forest. Without these birds the trees would have a much more difficult time defending themselves against pest outbreaks.

Maintaining the diversity of forest that these birds require for nesting and habitat needs will help ensure our forest remain in balance with insect populations and remain healthy!

The Red Spotted Newt is one of eight species of amphibians in New Brunswick. These amazing little animals begin and end their lives in temporary pools of water in the forest – called vernal pools. Adult red spotted newts are olive green in colour with bright red spots. They lay their eggs in temporary pools of water – vernal pools. Gilled larvae develop from the eggs. The larvae eventually develop legs and lungs, and turn into the bright red or orange “red efts” – the land phase form of the red spotted newt.

The red efts leave their vernal pools and take a long trip through the forest in search of a new vernal pool. Red efts require a certain amount of moisture in order to stay alive and need to stay under the protective canopy of the forest. Rainy days provide good days for traveling. On sunny days you are more likely to find a red spotted newt under an old dead log seeking shade, food and moisture. Red spotted newts feed on small insects and other invertebrates that live in the soil, forest litter and dead wood. Red efts play an important ecological role by helping to control invertebrate populations, and slowly releasing nutrients back into the forest soil. Red efts provide a highly visible indicator of mature forest.

The red efts journey through the forest ends 1 to 5 years later when they finally locate a new vernal pool. At the new pool the red efts turn into adult red spotted newts. They are then able to lay their own eggs and the cycle can begin all over again.

Natural disturbance in Acadian forest

The mixed wood forest in New Brunswick will suffer much less damage than a softwood dominated forest during a spruce budworm attack. The hardwood trees act as a buffer for the softwood trees in the stand.

The Acadian forest is typically not subject to large scale disturbances. Research suggests that fires would have been very infrequent in nutrient-rich hardwood forests. Fires in the nutrient-rich hardwood forests would have only occurred once every 800 to 1200 years. Forests with a higher percentage of softwood would have been more subject to stand replacing fires more frequently. Fires would have returned approximately every 250 years in lowland softwood forest dominated by red spruce.

Only individual trees or small groups of trees are typically affected by natural disturbances such as wind, insects or disease in the Acadian forest. The diversity of tree species in the Acadian forest makes this ecosystem naturally resistant to major disturbances. Occasionally large wind storms will cause major blow downs in the Acadian forest.

The small patch disturbances caused by insects and disease play a major role in creating the many layers of the Acadian forest. Insects and disease help create the dead wood, and small openings in the forest canopy to allow new trees to grow.

References

J. Loo and N. Ives. 2003. The Acadian forest: Historical condition and human impacts. The Forestry Chronicle. Mai/Juin. Vol. 79, No. 3. pg. 462-474.

A. Mosseler, J.A. Lynds, J.E. Major. Old-growth forests of the Acadian Forest Region. Environmental Review. 11: S47-S77.

Betts, M.G. and Loo, J. 2002. A Comparison of Pre-European Settlement Forest Characterization Methodologies. Forestry Chronicle. Vol.18. No. 3 123-129.