Soil: The Foundation of Your Yard and Your WoodsSoil is similar to the foundation of your house. It's not very noticeable, but there wouldn't be any thing growing on top with out it. In fact, soil is one of the most important factors in determining what kinds of tree and plant species grow well in a certain location.
The basic ingredients of soil fall into two categories: mineral soil (made up of clay, silt, and sand) and organic soil (made up of decomposing leaves and other organic matter as well as small invertebrates and other organisms). Soil moisture and air spaces in the soil also factor in to the kinds of plant or tree life a certain location can support.
The amount of sand, silt, and clay varies from place to place. Soils with a heavy clay content tend to be sticky and not well drained, though they can be quite fertile. Soils with a lot of sand tend to be gritty, not hold water very well, and usually are not very fertile. Silt laden soils feel smooth and tend to have good drainage. Loam is a fairly even mix of all three.
Decomposing trees and leaves form the organic layer (also called the O horizon). As the organic layer breaks down, it mixes with mineral soil from below to form the nutrient-rich topsoil (the A horizon) beneath the O horizon.
If you have ever dug a hole on your property, you probably noticed different colors of soil layers as the hole got deeper. The dark organic soil layer on top is usually about an inch thick. The organic layer and the layer below it (the topsoil) contain most of the nutrients that nourish a growing woodland. These rich soil layers are not easily replaced; it takes between 100 to 600 years to form an inch of topsoil.
Unfortunately, wind and water can erode away an inch of topsoil in a single year if the there are no trees, shrubs, plants, downed logs or other material to hold it in place. Once the topsoil washes away, it is much harder for plants and trees to grow at all and a cycle of erosion leaves the land nutrient poor. Soil sediment also is likely to end up in waterways, where it affects fish and other aquatic life.
Protecting Soil and Water
Forested areas tend to act like sponges when it rains. Trees and their roots hold water in the ground and release it slowly after taking up many of the nutrients that can become pollutants if they end up in streams or lakes. They also hold soil in place when it rains. Rain that hits bare ground runs off into waterways. It has no vegetative "sponge" to soak it up, so it picks up soil, pesticides, herbicides, and motor oil as it runs off. The soil particles, once suspended in a stream or pond, rob the water of dissolved oxygen needed by aquatic life. Some fish and other aquatic life in Maine tolerate low oxygen levels in muddy water. Many more do not. A muddied stream can ruin habitats for fish, frogs, and other water dwelling creatures. As anyone who fishes for trout knows, you can't catch a clear water fish in a muddy stream. A muddy stream doesn't look very nice, either.
If you plan to build a house or put in a woods trail, some planning is necessary to prevent erosion when removing vegetation near water or on slopes.
Any conservation measures you take will help keep the precious soil on the ground while also keeping water clean.
Conservation Measures That Prevent Erosion Include:
- Designing woods roads and trails to divert run-off into vegetation
- Planting trees and shrubs near waterways
- Alternating small lawn areas with landscaped shrubs, wildflowers, or ground covers
- Planting areas next to driveways and parking lots
- Seeding areas that were cleared during construction
- Covering bare soil to keep it from washing away
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For more information see Chapter Six of The Woods In Your Backyard
Being a Friend to Your Woods: Protecting Your Land from Damage (PDF: 920 KB)
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