What Is a Tree?
Trees grow, reproduce, and respond to their environment. Like all plants, trees manufacture their food through photosynthesis. Trees are in the family of woody plants which have cambium, a special layer of cells that allow the tree to increase in girth and are self-supporting with a single stem. Trees are perennials and can live for many years. The oldest known tree species is the Great Basin bristlecone pine, which is believed to reach ages of over 5,000 years old!
Food for trees is produced through a complex system starting with the leaves. Leaves produce sugar as a result of photosynthesis which combines carbon dioxide and sunlight. The by-product of photosynthesis that Trees produce is oxygen—a vital resource for other living organisms. Sugar that is produced runs down through the tree, under the bark down the trunk and to the roots of the tree. The sugar combines at the roots with minerals and water in the ground to move back up the tree trunk and under the bark back to the leaves to which starts the cycle of photosynthesis again. Along the way, minerals, water and sugar stimulate the growth and development of the tree or assist in its reproduction.
Tree Types
Trees can divided into two categories: deciduous and coniferous.
Deciduous Trees
are also known as broadleaf trees because the leaves are generally larger and wider than those of conifers. The larger leaf size means a greater surface area for photosynthesis, but it also means the leaf is too fragile to withstand winter conditions. Therefore, most deciduous trees drop their leaves in autumn.
Coniferous Trees
keep their leaves throughout the year, shedding only the oldest leaves. Usually these leaves are lower down on the tree and do not receive as much sunlight as newly developed leaves higher up. Some of the best-known members of the conifer family are pines, spruces, firs, and hemlocks. The cones of the conifers are its flowers.
Parts of a Tree
The crown of the tree is made up of the leaves and branches.
The trunk of the tree supports the crown and serves as a highway for food made in the leaves to travel to the roots and for water and nutrients from the roots to travel to the leaves.
The root collar is located at the base of the trunk just above where the roots join. Also called the root flare, due to the flared shape on some tree species, the root collar must always remain above ground when planting and mulching.
The roots of the tree support the trunk and crown, and also anchor the tree in the soil. They serve as a storage facility during the winter for the food produced by the leaves during the growing season. The roots also absorb water and nutrients from the soil for use by the tree.
Many wildlife species depend on trees for food, water, cover, or places to raise their young. You can help wildlife by planting trees and creating habitat in your community!
Benefits for Wildlife
From seed to dirt, trees are an important element of the landscape for wildlife. A tree's life cycle moves from seed to seedling to tree to snag to decaying to dirt. Along the pathway, wildlife and other plants are depending on the tree.
Living Trees
Trees support the lives of many large organisms. Trees are used for food, shelter, and sites for reproduction. Many animals also use trees for resting, nesting and for places from which to hunt or capture prey.
When the trees mature, animals are able to enjoy delicious fruits and foraging opportunities. During times of extreme heat or precipitation, animals can seek shade and shelter under the trees without being away from their food source.
Young trees can provide food for animals as well but need to be managed to ensure a percentage of new trees can grow and are not fully consume by wildlife.
Snags
Standing dead and dying trees, called “snags” are important for wildlife in both natural and landscaped settings, occurring as a result of disease, lightning, fire, animal damage, too much shade, drought, root competition, as well as old age.
Birds, small mammals, and other wildlife use snags for nests, nurseries, storage areas, foraging, roosting, and perching. Live trees with snag-like features, such as hollow trunks, excavated cavities, and dead branches can provide similar wildlife value. Snags occurring along streams and shorelines eventually may fall into the water, adding important woody debris to aquatic habitat. Dead branches are often used as perches; snags that lack limbs are often more decayed and, may have more and larger cavities for shelter and nesting. Snags enhance local natural areas by attracting wildlife species that may not otherwise be found there.
Decaying Trees
Decaying logs retain moisture and nutrients that aid in new plant growth and support wildlife such as soil organisms (earthworms, beetles, and other insects). Young trees may sprout from a single downed limb known as a nurse log. Decaying trees become softer as fungi, bacteria, and wood boring insects eat and break down the wood. The soft wood tissue of a nurse log offers an ideal substrate for many young trees during their initial growth and development. Logs also store energy and fix nitrogen. Furthermore, dead wood serves as a ground cover, lessening soil erosion and preventing animals such as deer from over-browsing plant seedlings.
Wildlife Need Trees
Many different types of wildlife depend on trees for food, water, cover, or places to raise their young. You can help by planting trees and creating wildlife habitat in your community for wildlife—like some of these:
You can symbolically adopt wildlife and support the Trees for Wildlife™ program.
