By Thembi Borras
When we walk in the forest we see the trees, the plants and perhaps mushrooms, mammals, reptiles, amphibians and birds, but beneath our feet is an ecosystem just as active and vibrant as the one we see above ground. Within this ecosystem, is a vast network of mycorrhiza, which literally means "fungus root". Mycorrhiza is the naturally occurring, non-pathogenic prolonged symbiotic association between fungi and the roots of vascular plants, in particular trees.
Mycorrhizae are separated into two groups, those that penetrate the cells of the root cortex, called endomycorrhizae and those that don't, called ectomycorrhizae. Douglas-fir can be a host to 2,000 different species of ectomycorrhizal fungi over the course of its life. Individual species of mycorrhizal fungi exist and behave as a function of a number of variables including soil fertility, aeration, soil temperature, pH, the presence of certain micro organisms, the presence of a specific host and the presence of specific mycorrhizal fungi mycelia or spores.
Mycorrhizae obtain simple carbohydrates from the host tree. In return, mycorrhizae improve nutrient availability and uptake by, in part, increasing the surface area placing more of the root in contact with soil nutrients. Carbonic acid, the result of fungal respiration and the solvent properties of fungal metabolic byproducts assist in the biochemical degradation of primary minerals in infertile soils. Pine seedlings, inoculated with mycorrhizal fungi, grown in prairie soil, aside from showing an increase in nitrogen concentration, demonstrated a two-fold increase in potassium and a three-fold increase in phosphorus. In addition, the exudates of the mycorrhizal fungus can stimulate growth. Moreover, mycorrhizae can serve as a biologic deterrent to pathogenic root infection by, in part, utilizing carbohydrates and other chemicals attractive to pathogens, by the fungal sheath acting as a physical barrier and by secreting antibodies which can inhibit or destroy pathogens.
Most healthy forest trees, conifers and broad-leaved trees alike, appear to have mycorrhizae. Moreover, their importance is greater felt in certain ecosystems. For example, the poor soils in the Amazon rain forest characterized by thin layers of litter and humus, below which are poor water logged clays, are able to support such a lush environment because the mycorrhizae efficiently recycle nutrients in the fallen leaf litter which would otherwise be leached away in heavy rains.
Introduction
The purpose of my blog is to share with you what I have learned based on my experience as a practicing forester in California and Washington and as the general contractor in our former homestead in Mendocino County, California and our current homestead in Kittitas County, WA. As a forester, for more than a decade, I have practiced forestry within the context of a strong land ethic that endeavors to balance economic return with the beauty, clean water, clean air, wildlife habitat, recreation and carbon storage offered by well managed forests. As home and property owners, my family and I challenge ourselves to make our footprint smaller, through conservation, sourcing quality materials from well managed sources as close to home as possible and use of alternative technologies within a budget. Thank you for visiting my blog and I hope that the information provided will help you as a steward of the forest and in the place that you call home.
July 9, 2006
Mycorrhiza
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