During the writing
During the writing of this book I became quite immersed in this subject and read far more deeply into soil biology and microbiology than I thought I ever would. Even though this area of knowledge has amused me, I doubt it will entertain most of you. If it does, I recommend that you first consult specialist source materials listed in the bibliography for an introduction to a huge universe of literature.
I will not make you yawn by mentioning long, unfamiliar Latin names. I will not astonish you with descriptions of complex reproductive methods and beautiful survival strategies. Gardeners do not really need this information. But managing the earth so that soil animals are helped and not destroyed is essential to good gardening. And there are a few qualities of soil animals that are found in almost all of them. If we are aware of the general characteristics of soil animals we can evaluate our composting and gardening practices by their effect on these minuscule creatures.
Compared to the atmosphere, soil is a place where temperature fluctuations are small and slow. Consequently, soil animals are generally intolerant to sudden temperature changes and may not function well over a very wide range. That’s why leaving bare earth exposed to the hot summer sun often retards plant growth and why many thoughtful gardeners either put down a thin mulch in summer or try to rapidly establish a cooling leaf canopy to shade raised beds. Except for a few microorganisms, soil animals breathe oxygen just like other living things and so are dependent on an adequate air supply. Where soil is airless due to compaction, poor drainage, or large proportions of very fine clay, soil animals are few in number.
The soil environment is generally quite moist; even when the soil seems a little dryish the relative humidity of the soil air usually approaches 100 percent. Soil animals consequently have not developed the ability to conserve their body moisture and are speedily killed by dry conditions. When faced with desiccation they retreat deeper into the soil if there is oxygen and pore spaces large enough to move about. So we see another reason why a thin mulch that preserves surface moisture can greatly increase the beneficial population of soil animals. Some single-cell animals and roundworms are capable of surviving stress by encysting themselves, forming a little “seed” that preserves their genetic material and enough food to reactivate it, coming back to life when conditions improve. These cysts may endure long periods of severe freezing and sometimes temperatures of over 150 degree F.
Inhabitants of leaf litter reside close to the surface and so must be able to experience exposure to dryer air and light for short times without damage. The larger litter livers are called primary decomposers. They spend most of their time chewing on the thick reserve of moist leaves contacting the forest floor. Primary decomposers are unable to digest the entire leaf. They extract only the easily assimilable substances from their food: proteins, sugars and other simple carbohydrates and fats. Cellulose and lignin are the two substances that make up the hard, permanent, and woody parts of plants; these materials cannot be digested by most soil animals. Interestingly, just like in a cow’s rumen, there are a few larvae whose digestive tract contains cellulose-decomposing bacteria but these larvae have little overall effect.