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“Some years ago, scientists blocked off a small section of forest soil in New York state and removed the top layer of earth to a depth of one inch. In all, there was an average of 1,356 living creatures present in each square foot… Had an estimate been made of the microscopic population, it might have ranged up to 2 billion bacteria and many millions of fungi, protozoa and algae – in a mere teaspoonful of soil.”
Peter Farb, The Forest
Although it is often overlooked, forests are only as healthy as the soil they grow on. Soils are full of a wide variety of living organisms, again each with roles to play and susceptible to poisons. If we remove too many nutrients from the site, or degrade the soil, we can create the same results that humans get from drinking polluted water or eating poor quality food. When nutrients are lacking, unhealthy trees can easily succumb to insects, diseases and atmospheric pollution that stronger specimens might have weathered.
Soils are probably the most complex and least understood part of natural systems. Soil degradation is not easy to measure. It involves a combination of many effects; loss of biological diversity within the soil itself, destruction of soil structure, loss of nutrients and the enhanced development of acidic soils known as podzols.
Traditional harvesting on farm woodlots, while slowly degrading the quality of trees on site by removing only the best stock, were much less harmful to the soil than today’s methods. Individual trees or small groups were removed and a lot of brush remained on site to protect the soil and provide nutrients for the next crop. Small equipment was used, often in the winter, creating less soil compaction. Contrast this with large-scale clearcuts where brush is burned, or whole tree harvests, where almost all above ground brush is removed. In both cases, large amounts of nutrients are lost and heavy machinery is used that can lead to severe soil compaction.
Gordon Robinson, forester and author of The Forest and the Trees:
A Guide to Excellent Forestry, worries about increased exposure to solar radiation and evaporation after clearcuts. “The normal soil life of fungi, bacteria, worms and all types of micro-scopic plants and animals is destroyed or at least greatly changed.” Since health and vitality are important factors in preventing tree disease, trees growing on degraded soil are more susceptible to insect and disease damage.
What you can do: