2. Bark - The tough outside covering of a woody stem or root

3. Biodegradable - Being able to be broken down or decomposed by natural means

4. By-product - Something that is made in the process of making something else

5. Cambium - Clusters of tree cells that produce a new layer of wood and an new layer of bark each year, thus forming the tree rings we can count to tell the age of a tree

6. Carbon Dioxide - A colorless, odorless, incombustible gas that is formed during respiration, combustion, and organic decomposition

7. Cells - The basic building blocks of living things

8. Cellulose - The material that makes up plant cell walls

9. Chlorophyll - The green substance found in leaves and needles

10. Compost - A collection of organic scraps and garbage that decays and becomes good fertilizer

11. Conifer - A cone-bearing tree

12. Decay The coming apart or rotting of organic material

13. Decompose To decay or come apart

14. Ecology - The study of how plants and animals interact with their environment

15. Energy - A source of usable power, such as sunlight or food

16. Environment - The conditions or elements that surround an ecological community or its members

17. Erosion - The wearing away of the soil, usually by wind or water

18. Feedback - The return of information about the result of a process or activity. It often results in change by the receiver of the feedback information.

19. Fiber - Thin threads that bind together to form animal and plant matter

20. Habitat - The place that is home to a plant or animal

21. Heartwood - The hard, inactive wood at the center of the tree

22. Hydroelectric plant - A place where electricity is produced by the energy of rapidly moving water

23. Landfills - Places in our communities where garbage is unloaded and then covered over with dirt and packed down

24. Lignin - The sticky substance that binds plant cells together

25. Natural regeneration - The process by which seeds sprout to produce seedlings in the wild (without the use of a nursery to cultivate them)

26. Natural Resources - Things we use that come from the earth

27. Organic - Material made of carbon; made of living matter

28. Oxygen - An element found freely in nature that is necessary for humans and animals to breathe and is needed for nearly all combustion to occur

29. Photosynthesis - The process of producing food for trees by combining sun light, water, chlorophyll and carbon dioxide

30. Pulp - The mash that forms when wood chips are cooked

31. Recyclable - Being able to be utilized again, often by being restructured into something else

32. Relic - An object with historic value that has survived from the past

33. Renewable - Having the capability of replenishing itself

34. Riparian zone - The area along a river or stream

35. Roots - The tree parts below ground that hold the tree upright. Root hairs, which push their way through the soil and absorb moisture, send water and nutrients up into the tree.

36. Sapwood - Wood that lies between the cambium and the heartwood. It acts as a major conductor of water and minerals for the tree

37. Spawning - The producing or depositing of eggs by fish

38. Web of Life - The network of relationships that interconnect all species of an ecological community

39. Wild fire - A fire that is burning out of control