Forest Edge Ecology
The progression of plant life on a newly developed house lot—if it were left to time and serendipity —would go something like this. Annual weeds like shepherd's purse and mustard, appearing hither and thither at first, would eventually grow in profusion. The setting of seed initiates dieback in annuals, which in turn alters the carbon-to-nitrogen (C:N) ratio upward as lush stalks turn brittle and brown. Decay goes slowly at first, but eventually the accumulation of organic matter creates a shift in plant composition. Dandelion and plantain are among the first perennials. Grasses and taprooted volunteers like wild carrot and curly dock get a foothold and never look back. Organic matter continues to build. Goldenrod and raspberries arrive to stay. More carbon is stockpiled as ever-woodier stems decay. Tree seedlings start to appear: species like pin cherry, brought by birds; white birch and willow, carried by the wind; and perhaps apple if deer droppings or a thrown core rolls onto the scene. As woodsy plants grow, shade lessens the grip of perennial weeds. Blackberry canes and short-lived tree species begin to add lignin to the humic crescendo. Hardwoods and softwoods alike find increasingly hospitable ground. Along the very edge, where the bright sunshine can never be denied, those apple trees come into their own.
This is what we humans see... but it is far from the whole story.
The soil food web
The soil in the beginning of this plant progression saga could essentially be viewed as an uninhabited medium following that last scrape of the bulldozer. Now begins a biological onslaught of bacteria, fungi, and other soil dwellers that will gradually transition this ground from barren substrate to living earth. Those first weeds produce digestible biomass that becomes organic matter; the microorganism community transforms and releases nutrients from this organic matter so that even more plants can complete the renewal cycle. Bacteria tend to utilize simple organic compounds, such as root secretions and fresh plant residue. Fungi will utilize more complex compounds, such as cellulose, lignins, and soil humus. The ratio of fungi to bacteria begins to shift as succession plant species take over, which in turn provide more fibrous plant residues on which an even greater diversity of fungi thrive. The composition of plants adjusts as the soil becomes increasingly fungus-dominated.
We deem this interaction, which makes life on earth possible, the soil food web. Billions of living organisms exist in a single handful of soil. Such mind-boggling numbers serve to remind me that I am but one member of a huge interdependent team striving to orchard wisely
on my farm. The progression that takes place when microbial feeders restore soil balance—and just where that balance point lies for different plant species—spells out a far more accurate way to grasp plant dynamics than does available mineral fertility as indicated on a typical soil test. All soil organisms work together as a living system to support plant health by decomposing organic matter, cycling nutrients, and improving soil crumb structure. The health of untold organism communities within this living web plays a pivotal role in both enhancing and protecting the physical reality of fruiting trees and berries.
System health springs from the biology in the soil; it's as simple as that. Learning more about the soil food web beyond the basics of fungal dominance won't be necessary for fruit growing per se, but I would encourage it. The humic system performs best when fungi and bacteria are associated with microvores
such as protozoans and nematodes. All participants in the soil food web play vital roles in the assimilation and mineralization of nutrients for plant growth. The desire to serve this web of life in the soil—for that's what being an enlightened fruit grower really entails—springs from knowing your friends. Choosing to honor and support biological connection will help you avoid the many props required by a sick system. How we travel along this holistic high road begins with understanding what fungi like.
Interdependent and interconnected networks of organisms interact to make life possible. The soil food web encompasses the microbes and arthropods that ultimately provide balanced mineral nutrition for fruiting plants and thus promote overall tree health. Go, biology, go!
Fungal dominance
The integrated health of any fruit ecosystem correlates directly to the ratio of fungi to bacteria found in the living soil. Orchard soils ideally contain a fungal presence ten times higher than that of bacteria. This ratio defines forest-edge ecology, and it's this ratio that is going to drive all the recommendations about soil nutrition and understory management that lie ahead.
First, though, let's be clear about what we're talking about. fungi">Fungi are...
Mycorrhizal outreach through an extensive mycelium network is a major biological asset in the healthy orchard. Balanced mineral nutrition is assured when these fungal allies reach well beyond the rhizosphere (root zone) of fruiting plants. Here's a mind boggler: A handful of woodsy soil contains over twenty miles of these interwoven hyphae!.
Some of the participants in this arboreal food web are soil dwellers stretching their legs, so to speak; other canopy organisms are specific to particular plant species and intertwined with arthropod association. Certain epiphytic fungi are especially intriguing, having mycelia that run along the inner bark and promote overall tree health. Such arboreal relationships will play an integral role when we discuss holistic disease management in the orchard. Leaf colonization provides the desired competitive environment and—perhaps just as telling—phytochemical stimulation by which a plant can stand up to disease pressure all the more. Arboreal fungi are among the subtleties I refer to when stating that the best organic methods depend entirely on orchard health being in place across the board.