FOREST WALK
Energy and nutrients move through trophic levels in the forest ecosystem.
Students should understand the concepts of trophic levels, food
chains and food webs. Point out the importance of decomposers
as well as the more obvious producer and consumer levels.
As you discuss each organism with your group of students, ask them to describe its distribution in the forest. Ask the group to suggest biotic or abiotic factors that may affect the distribution of the organism (e.g. light intensity, associations with other organisms, availability of moisture, type of substrate, etc. Make sure that you discuss this for at least one member of the plant, animal and fungal kingdoms.
To start your walk head across campus to the Shell station. Walk carefully
across the road (watch for traffic!) and stop just beside the Shell station.
A number of features are described below, but feel
free to point out any other features of interest.
The first stop is the alder grove to the right of the
Shell station. Alder represents an early stage in forest succession,
the predictable sequence of replacement of the plants and other organisms
that make up a forest community. Discuss succession (primary versus
secondary) with your group, and explain why alder are a successful pioneer
species. Alder plants grow fast, quickly moving into and growing in newly
opened areas, such as logged areas. These trees are almost 30 years old,
the same age as SFU. The university gave them a start when they cleared
the old growth from the mountain top. Red alder seedlings are intolerant
of shade. The seedlings grow only in full sunlight. Nodules on alder
roots are packed with mutualistic bacteria. These bacteria fix nitrogen
into a form that is usable by the trees.
Walk down the trail that angles down from the Shell station and look at the shrubs beside the trail.
Indian plum is the first tree to come into leaf and
flower in the spring. Why does Indian plum flower so early? Southern B.C.
represents the northern limit to the distribution of this species, which
is common in Oregon and Washington. Indian plum is rarely found in exposed
areas this far north. The larger trees create a protected microclimate
that offers protection from frost.
On your left is salmonberry. This plant is clonal.
Above ground runners produce new upright plants, allowing a rapid spread
of this plant over a large area by asexual reproduction. Many of the shrubs
we see in the forest are clonal, including trailing blackberry and most
of the other berries. Discuss with your students the possible benefits
of clonal growth. How do we define an individual plant? Is it one upright
salmonberry plant or the whole clone? Salmonberry, with its showy flowers
of mauvey-red, flowers quite early in the spring. Chickadees feed on the
nectaries at the base of the flower, pulling off one petal to feed on insects
that visit the nectary and serve as pollinators.
Point out the cedars to the students. The cedars and alders probably
got started together. The fast growing alder is taller now, but the cedar
will eventually tower over it and shade it out. Cedar is important in continuing
forest succession, replacing alder as the next successional stage.
The broken alder trunks are testament to the massive
blowdown that took place in the Fall of 1994. Use this dramatic pile of
alder trunks to discuss the costs and benefits of deciduous vs evergreen
