Organic matter in soils helps maintain a healthy forest ecosystem

Forest and associated wildlife species health are directly related to the relative proportions of four basic ingredients in the soil; mineral particles, organic matter, water and air.

Soil is more than simply the dirt beneath your feet; it is a living community of microorganisms, water, nutrients, minerals and air. Plants root systems move through this soil community and take up the components needed for plant growth and development by absorbing them with the water they are dissolved in. Organic matter is another important component of soils.

Organic matter, which is made up of partially decomposed plants and animal matter, plays an important role in providing for soil structure, therein improving soil health. In clay soils, which are composed of small particles that are packed tightly together, there is minimal space for air or water movement.

Organic matter helps separate the clay particles, loosening the soil for easier root development and allowing for better water movement throughout the soil. In more sandy soils, organic matter fills the openings left by the larger sand particlesIt functions like a sponge by holding water and helping to prevent dissolved nutrients from leaching out of the soil.

In gardens, organic matter can be added by tilling in compost. Lawns can be helped by using a mulching mower, which allows the clippings to break down and work into the soil. Farmers will incorporate animal waste or work in green manure to increase the organic matter in their croplands.

In a forest setting it isn’t generally practical to physically add organic matter to the soil.  However, landowners and forest managers need to be mindful to not reduce the amount of plant material available which, over time, will break down into soil organic matter.  Leaves, needles, branches and tree tops gradually decompose, providing nutrients that support future tree growth in addition to adding to soil organic matter.

Best Management Practices guidelines for Michigan’s forests recommend that one-sixth to one-third of the total volume of trees being harvested from forestland should be left as residue to provide for sustainable forest growth and health.

More detailed information on forest soils and nutrient cycling can be viewed in the Michigan State University Extension Forest Ecology Series Bulletin E-2637 Soils and Site Productivity.

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