Tree as a living island
Trees are one of the most visible and magnificent among all land organisms. Trees are one of the longest living organisms in the world. Some of the oldest oaks in Poland reach an age of more than 600 years. The oldest recorded living tree - a bristlecone pine - grew in the mountains of California and reached an age of over 4700 years! It makes trees the most stable and long-existing element of land biodiversity. In the landscape each single tree looks like a green island hidden in the blank spaces of old maps.
The Peppered MothBiston betularia is perfectly camoflaged on a birch-trunk. Photo: Frode Falkenberg.
What a great temptation for organisms of crowded ecosystems to colonise such a promising island! Like a piece of dry land for a ship-wrecked man, such ‘green islands’ offer lots of natural goods: space to live and rest, food, water and shade. Sunshine filtered through dense foliage gives good camouflage against predators. You would be surprised how many animals, and plants have come to use these elements of our tree during their life cycle! They compete with each other, eat leaves and fruits, hunt prey, lay eggs in nests or hollows and dig shelters in the trunk or under tree roots. Tree bark can be covered by a dense garden of lichens and mosses.
The fallen leaves and branches rot and crumble, offering hiding places and food for a vast array of fungi, ants, woodlice, beetles, earthworms and other forms that live mostly or exclusively in this habitat. When the tree is cut out or fallen, the soil and
ground litter dries out and warms up creating a new environment for a different array of animals, fungi and microorganisms that are not successful in the darkness of a closed canopy or forest.
Subjects: Biology, English, Citizenship.
- To observe different relations in the community connected with our tree.
- To understand how energy flows through trees.
- To understand the relationships between insects and plants found on trees and their role in the tree ecosystem.
- Guide to functional groups
- Observation sheet 1 and 2
- Binoculars for observation of birds
- Magnifying glass for insects
- Sample boxes
- Collecting pot
- Sweep net
There are several good starting questions for this activity. For example:
- Why are there so many species?
- Why do animals and plants use trees in so many ways?
- Why do some species sing in the summer time while other species in the early spring?
- What happens when humans behave in unsustainable ways?
- Why are all these tree dwelling plants and animals important?
- What would happen without pollinators such as bees and flies?
All activities should bring us to important reflection: Destruction of one single tree also means a “death sentence” to several other species!
Preferably the tree is the same as for phenological observation. Minimum and maximum options:
- Time for observation: one lesson (30 to 45 minutes)
- Introduction (Explanations, dividing into groups etc.)
- Handing out tasks and equipment
- 15 to 30 minutes for observations and investigations (see Field protocol sheet)
- Taking pictures
- Summarizing by the working groups
- Monitoring throughout the year: observing in 4 different phenological phases
- When the trees have their first leaves
- When the tree first flowers
- When the berries are ripe or when the seeds have developed
- During winter
- 10 min per week which can be done in lessons of as an extra-curricular activity outside of classroom sessions.
Out of classroom observation
- Start the observation from a distance of 50 metres. Watch the birds, squirrels or other animals using binoculars. Note them in the Field protocol (observation sheet 1).
- Reaching the tree observations should cover all accessible elements of the tree and the soil surface under the canopy: leaves, trunk, branches, surface roots, deadwood, dead leaves. Note the observations in observation sheet 1.
- Trunk: Which animals, plants, lichens, fungi, holes and cavities can be observed on the trunk?
- Leaves: Examine leaves on and under the tree from both sides of the leaf. Which organisms, prints of eaters (galls) and traces of mining insects can be observed?
- Soil surface (1 m² under the tree) including visible roots: Look for earthworms, woodlice and other decomposers. Examine the holes under the roots. Look for traces of animals eating fruits (footprints, faces, rest of seed shells).
- Branches and canopy: What can be observed from the ground (nests, mistletoe etc.)?
Of course it is impossible to count or classify all species. Try to group organisms by the role which they play in the community associated to your tree. The functional key will help you to place observed species in the functional categories listed on observation sheet 2.
You will need to allow time to analyse your results. Try to encourage students to move from their recording of data to expressing their own views and opinions based on data. Here are some suggestions:
- Find the appropriate functional group for each organism you observe: species eating the leaves, wood, fruit, feeding on flowers, pollinators, decomposers, predators, temporarily living and breeding, visitors. Fill in observation sheet 2 (Functional groups). Are there any relationships between the functional groups?
- Discuss interrelationships among functional groups and between the tree and the species.
- Discuss the situation if the tree was removed by man or fell down and left to decay naturally. What happens to the community living on the tree?
- Which pollinators did you observe? Why are pollinators so important?
- Discuss the situation when the tree buds earlier in the season - what are the consequences for the species connected to the tree? What about other changes?
- Do the communities living on trees change throughout the year (changing seasons)? Discuss your observations.
- Compare the results among the countries of the BEAGLE project.
- How could climate change affect the community living on the tree?
- Scientific research projects investigate the impact of changes in climate and land use on tree distributions. They use scenarios to describe “possible future worlds”. You can obtain more information here. The paper European phenological response to climate change matches the warming pattern might also be useful.
- How can your behaviour contribute to a more sustainable development of your area?