Forests are complex ecosystems featuring a diverse array of organisms ranging from enormous trees to tiny fungi. Within the forests there are unique niches occupied by well-adapted plants and animals. Forests are classified as coniferous, deciduous or mixed, based upon the mixture of trees in the ecosystem.
Coniferous trees have a variety of adaptations that allow them to successfully withstand long, cold winters. Conifers have slender, tough, waxy needles instead of leaves. The needle's small surface area reduces water loss and resists freezing. Winter air is often dehydrating because cold air cannot hold as much water as warmer air. Since water expands when it freezes, many plants sustain irreparable damage when ice forms inside their cells. The thick sap, also known as pitch, has a very low freezing temperature, which prevents the tree's cells from rupturing. The needle's waxy outer layer prevents wind induced water loss and rapidly sheds snow. The tree can replace old or damaged needles. Some conifer needles contain chemicals that are toxic to insects, which prevents sever insect infestations. Spruce trees are vulnerable to insect damage because they lack these natural insecticides.
The conifer's needles remain green all year allowing photosynthesis to occur throughout the winter. Although the needles of conifers have less surface area than the leaves of deciduous trees, these conifers can produce some sugar every day. the sticky surface of the needles traps airborne minerals that will be washed off when it rains. These minerals, which concentrate near the tree roots, make it possible for conifers to grown in nutrient-poor soil. Unfortunately, these adaptations have also made conifers more susceptible to air pollution, especially to damage from acid rain. The needle size, shape and arrangement on the branch as well as the cone shape help identify trees.
Unlike the conifers, deciduous trees are difficult to identify by shape alone. Leaves,flowers, and fruit are essential to complete the identification process. Deciduous trees lose their leaves in the fall to protect the tree from dehydration and frost damage during prolonged periods of freezing temperatures. Not all broad-leaf plants are deciduous. Some leafy plants have adaptations that allow their leaves to survive short periods of freezing temperatures. In mild climates trees can maintain healthy leaves throughout the year.
Ecosystems that are dominated by trees have characteristic microhabitats. the ground is often shaded and cooler than the surrounding area. the plants that grow in this understory have adapted to a low light environment. The forest canopy contains the greatest biomass. Animals take advantage of the wide variety of niches in the forest.
