Benefits of Mycorrhizae for Forest Systems
Mycorrhizae: The symbiotic association between plant roots and root-dwelling fungi.
Mycorrhizal fungal networks perform a function in forest systems that cannot be understated, and are a critical part of natural systemic health: more than 90 per cent of plant species in natural areas form a symbiotic relationship with the beneficial mycorrhizal fungi.1 Evidence suggests that the mycorrhizal habit evolved as a survival mechanism for both the fungi and the higher plants in the association, allowing each to survive in the existing environments of low soil fertility, periodic drought, disease, extreme temperature, and other natural stresses.2
Mycorrhizae’s fungal filaments increase the surface absorbing area of roots 100 to a 1,000 times,3 promoting vigor by mining the soil for nutrients; some plants that are well-colonised by arbuscular mycorrhizal fungi can grow just as well with only half the amount of phosphorous available in the soil as that required by plants that do not have these fungi within their roots.4 Furthermore, mycorrhizae cycle nutrients which minimize nutrient loss, raise plant defense through antibiotic excretions, strengthen root systems, increase plant growth speeds, and improve yields and reliability. Mycorrhiza also regenerate and improve the broader forest system by increasing soil diversity and chemistry, and by purifying contaminated soils.
Myccorrhizal action is one of nature’s invaluable tools, ensuring overall system resilience and fortitude. Replicating nature’s dynamic symbiotic arrangement between plants and fungi is a primary priority for permaculture designers attempting to mimic nature’s success.
Appropriate Mycorrhiza Application
There are four primary types of mycorrhizas: ectomycorrhiza, arbuscular mychorrhiza (also known as vesicular arbuscular mycorrhizas), ericoid mychorrhiza, and orchid mychorrhiza. Each ecosystem usually has a single dominant mycorrhizal association, and each plant species typically forms only one type of mycorrhizal association. Tropical forests may contain more equal proportions of plant species that form arbuscular and ectomycorrhizal associations. Most annual agricultural plants form arbuscular mycorrhizas. Ectomycorrhizal associations are less common in disturbed ecosystems and are more frequently observed on perennial plants. Horticultural species form a variety of mycorrhizal associations, depending on whether they are ornamentals (all types of mycorrhizas are represented in this group) or vegetable and orchard plant species (most of these form arbuscular mycorrhizas).
Such associations are generally beneficial to both the plant and the fungus, with nutrient exchange between the partners. However, under some conditions, at least for arbuscular mycorrhizal (AM), there is no beneficial effect and plant growth can even be reduced.6 The outcome of AM upon plant health is due to soil conditions; plants growing in a phosphorous-rich soil (an important impact of AM fungi on plants is the alleviation of phosphate deficiency) will not benefit by an AM association. In locations of excessive phosphorous, the fungus appears to remove carbon from the plant to an extent that is detrimental to the growth of the plant. Therefore, only plants growing where there is an inadequate supply of phosphorous will benefit. Furthermore, plants which require relatively large amounts of phosphorous (extremely fast growing, leafy plants), which also have a more course root architecture and thereby less capable of extensive exploration for nutrients, will tend to benefit more from an AM fungal association. Research indicates that the presence of AM fungi is worth the potential detriment to the associated plants; altering the amount of phosphorous in the soil, or by adjusting soil conditions which affect fungal growth, will result in striking a balance which both plants and fungi will find suitable. In addition, even if no nutrient benefit is gained from the presence of AM fungi, there will be an improvement to the physical state of soil because hyphae help to stabilize soil aggregates.7
Ectomycorrhiza (EM) fungi are commonly associated with long-lived perennial plants and are much more straight-forward in regards to their interactivity.
Establishing Mycorrhiza Networks:
Mycorrhizal networks are easily established in orchards, food forests, and reforestation projects. The mycorrhizal inoculant only requires direct, physical contact with the plant roots: applied during transplanting, worked into beds, mixed into potting soil, watered-in, applied as a root-dip, or probed into the root zone of existing plants. The type of application depends upon the conditions and needs of the applicator. Two options exist for establishing mycorrhizal networks.
Commercially Available Products
Two products are recommended: one soluble, one granular. The soluble formula is to be mixed with water in order to create a solution, which is applied directly to plants in pots or in ground. The granular formula can be applied directly to plants, as well as broadcast. Cold, dry storage maintains viability up to 24 months.
At Walkers Reserve, the mycorrhizae will be applied in the nursery to all plants. Application in the nursery makes the widespread use of the fungi over time very easy, and allows the plants to benefit from the application of mycorrhizae from the very start.
|Product Name||Application Rate||Directions|
|Plant Success Soluble||1lb per thousand 4 inch plants||1-2 tsp per gallon of water for solution:*4 inch pot > 6 oz*1 gallon > 10 oz*5 gallon > 1 gallonrepeat process every 2 weeks|
|Mycorrhizal Granular||10-20 lbs per acre||*Broadcast 10-20 lbs per acre*1 tsp per row foot*1/2 tsp at each cutting*1-2 tsp at each transplant with 20 ft or smaller canopy diameter|