When Earthworms Are Not Helpful

The Perfect Nursery Environment The forest floor is a rich bed of slowly decomposing annual leaf litter slowly worked on by fungi and bacteria. This thick carpet is called the Duff Layer. It can be up to 10cm deep and is the perfect nursery bed for young saplings and a multitude of indigenous understory plants; a gentle climate-controlled environment that is rich in slowly decomposing elements that give provision and protection to the new life. Some seeds need to take as long as 2 years to fully germinate, and the naturally created loose, organic, forest floor gives the best environment for this. Below this rich mulch unique soil layers develop. Earthworms Eat The Blanket The beautiful black vermi-composted topsoil we so covet in our gardens is not desirable on a forest floor. The Duff Layer that so intricately supports life on a forest floor disappears when earthworms move in. The environment that once offered slow-release nutrients via fungi and bacteria, and the moisture and temperature control of a light bed of fallen leaves is no longer present, and as the environment changes so does the life it supports – from the micro-cosmic to much larger creature life – in a domino effect. Soil Layers Beneath A Rich Mulch The O-Layer [Organic Layer] is the rich carpet of annual fallen leaves, twigs, bark, and even some dead branches and trees, that gives that rich earthy forest floor we are so familiar with as we walk over this spongy layer. The A-Layer is usually distinct and separate just below the mulch; a thin rich topsoil with a large organic constituent that has formed slowly over time though fungal and bacterial action. The E-Layer forms right beneath the A-Layer, a mineral soil that is more like parent soil, but water has leached the nutrients from the A-Layer down into this layer and a definite gradient of colour can be seen throughout – from darker to lighter. The B-Layer is more like the parent material except some leaching of dissolved minerals will have affected the natural shade of yellow, brown or red. This layer can be thin or thick depending where it is located. The C-Layer is the parent material. The C, E, and B Layers are all the same soil material, but the C-Layer has not been modified by water leaching in any way. When Earthworms Invade A Forest Floor Earthworms work wonders in turning organic matter into beautiful dark, rich topsoil. The O-Layer disappears and is replaced by a deep A-Layer that is thick and heavy with nutrient, but water will not penetrate and be retained as easily as on a well-mulched layer. Run-off causes soil erosion and young plants that needed the gently maintained micro-climate offered by the thick, slowly degrading mulch of a Duff Layer can no longer germinate. The environment begins to change. This is not desirable if the forest is to be sustained. The O-Layer In A Food Forest? I never thought there would ever be a place I did not want to see the beautiful action of the earthworm, but there is a place; the natural forest floor. When considering the Food Forest floor I have realised that we have a managed forest here, where the chop-and-drop technique can always ensure a healthy mulched O-Layer under the trees. However, in my experience, a heavily leaf-mulched area where sunlight is not filtered through a strong top-story will not allow water to permeate sufficiently through the mulch to the soil below because the direct sunlight will evaporate it too fast. Chop-and-drop is a deliberate speeding up of natural cycles where trees and shrubs are sacrificed for favoured species in food production. The layer that is laid this way is not the same as a natural forest floor which is largely annual leaf drop and water penetration is good with the rougher texture. I have had spare leaves collected from elsewhere that I laid in my food forest, to the detriment of the sun-soaked areas, because I laid it too thick. The mulch of O-Layer must be carefully monitored and managed according to how mature the Food Forest is. Not difficult, it soon becomes obvious what is needed. Until next time, Chelle References: