Woodland Management, Agriculture, Gardening and Grounds Maintenance causes the thin layer of topical organics to be depleted through; the conversion to pasture or lawn, the regular grazing or mowing and removal of cattle, hay or clippings, gardening whereby litter is removed and the burning off of twigs and leaves, particularly in Fuel Reduction Burns.
It is this layer of organic mulch that provides the primary drive of soil health and consequently plant health. The organic layer is infact many layers – one on top of the other.
The top is the most recently shed plant parts. This comprises all the various regularly shed plant parts such as leaves, twigs, flower parts, fruit and bark. From time to time larger limbs or whole trees fall, again being applied to the surface of the mulch.
All the shed parts contain carbohydrate, starch and minerals that sustain other life forms. These life forms, beetles, slaters, ants slugs, snails etc. all use the organics as a food supply. All these animals excrete wastes high in nutrients and they will eventually die and also supply nutrients. These nutrients, moisture and residual organics are colonised by bacteria and fungi that also break down the organics back to their building blocks.
Importantly the topical organic matrix that also becomes partially incorporated into the mineral soil traps and holds moisture. Within the moisture that has fallen as rain are minute traces of nutrients. This inflow of nutrient salts, over time, sustains the nutrients held within the plant community growing on the site. Plants and trees recycle nutrients within their system, when unwounded, withdrawing nutrients from unproductive sections that are destined for shedding.
Healthy wood is substantially deionised, firstly as a management of finite nutrients and secondly as a protection process by leaving little behind for fungi and mould to capitalise on should they gain access. Shed plants still have the nutrients built into the tissue structure and these are what are recycled by decomposition.
The organic layer also acts as a flow retardant during periods of rain, helping the rain to soak in rather than run off. This water soaking in flushes nutrients down deep into the soil profile. Thus they become available to the trees deeper root system.
The loss of this mulch layer causes unusual levels of aridity within the thin topsoil. The lack of an organic layer also causes water from rain events to run off rather than soak in, further depleting the soil. The topsoil and organic layer is the most important layer.
Compaction, dry conditions and lack of a natural organic layer substantially reduces the quantity of beneficial mycorrhizal fungal roots, which are imperative for healthy plant growth. Climax vegetation plant growth is limited, not only by water, but also by nutrients. In droughts litter builds up but does not decompose thus increasing the fuel loading. In natural forest floor not subject to fuel reduction burns the higher humidity in decomposed material increased decomposition of ne litter. Thus regular short rotation fuel reduction burns promote further fire risk.
Without proper levels of easily available nutrients, a plant’s growth becomes stunted, vigour is reduced, and pests and diseases move in leading to the death of the climax vegetation and the return of the soil profile from organic to mineral. Climax vegetation is composed of the tree we so want to keep, but do our utmost to destroy. Pioneer species that follow this process are short lived, normally nitrogen fixing mostly short multi stemmed shrubs or small trees.