Coniferous vs. Deciduous

Transcription

1 The purpose of the leaves on a tree is twofold: the leaves help exchange gases (they inhale carbon dioxide and exhale oxygen; now go thank a tree), and to collect sunlight for photosynthesis. Small openings on the leaves, called stomata (singular: stoma), can open and close, allowing CO2 into the tree s circulatory system. CO2 and sunlight combine to make essential sugars for the plant, but the open stomata also lose water during respiration. In a tree s ideal world, it would be bright and sunny all year long with high humidity. That way, the leaves could collect lots of sunlight without losing a lot of water, and not have to survive a winter. Since that only happens in the tropics, where competition for those amazingly available resources is high, trees have evolved some pretty neat methods of surviving winters in the rest of the world.

2 Eastern hardwood forest, primarily made up of deciduous broadleaf trees. Let s do some basic vocab first. Deciduous = the dropping of a part that is no longer needed, in this case leaves Coniferous = bearing pinecones, most of which are evergreen Evergreen = retaining leaves year round, therefore remaining forever green Broadleaf = a thin, broad leaf structure with a good deal of surface area Needle = a thin, long modified leaf typical of conifers

3 The difference in survival strategies between coniferous and deciduous trees boils down to two basic things: energy and soil. Deciduous trees live in areas where the soil is pretty nutritious. This is critical for deciduous trees because it takes a big nutrient boost to produce hundreds or thousands of new leafy suncatchers. And broadleaves do, in fact, collect an enormous amount of sunlight compared to their coniferous cousins, meaning that they can photosynthesize at high rates through the warm season. Then, when autumn rolls around, the leaves can be dropped essentially on top of the tree s roots, where they ll recharge the soil with nutrients when decomposing. During the winter, most of the energy in the tree moves into its roots and it has a vastly reduced need for food, water, and growth during that time. Beech leaves. Coniferous trees are typically evergreen. They retain their needles year-round, replacing them slowly throughout the year rather than all at once. Needles have a variety of benefits: they are smaller, more watertight and more windproof, and can photosynthesize all year long. Needles don t collect a lot of sunlight themselves, but overall the tree can continue photosynthesizing at a reduced rate whenever sunlight is available during winter months. Needles, with their reduced surface area, are harder to destroy and less tasty to insects. Since conifers don t drop all their needles at once, they don t need a big nutrient boost in the spring which is good, because conifers typically inhabit areas with poor soils and less water than their deciduous cousins.

4 Match the following pictures with their classification: Deciduous Coniferous A Broadleaf B Needle C D

5 Answer True or False for the following questions: 1) Coniferous trees absorb great amounts of sunlight in the summer. 2) Evergreens are named because they hold onto their leaves all year long, keeping them green all the time. 3) For deciduous trees, most of the photosynthesis happens during the summer months. 4) When coniferous trees drop their leaves in the winter, the leaves decompose and are then absorbed by the roots as nutrients. 5) Needle-shaped leaves are easier for animals and insects to eat because they are smaller. 6) The stomata are tiny openings in the leaves that allow CO 2 into the leaves of trees, so it can be changed into oxygen. In your own words, write a brief paragraph describing the differences between coniferous trees and deciduous trees.

6 Research one type of deciduous tree and one type of coniferous tree in Alberta, and write a brief description of them. Make sure you include the name of the tree, where it can be found, and the type of leaves on the tree. Coniferous Deciduous