Native Plant Communities and Companion Plantings
The
plants, their roots, the mycorrhizal partners (fungi) and the
other associated microorganisms are interlinked and support each
other, sometimes for vast areas.( Mycorrhiza is a symbyotic
relationship between plant roots and fungi.) This interconnection
can extend across a whole plant community, even if that community
runs for 200 miles. The trees are all the same species and the
dominant fungus is the same. It is fascinating to see how far the
research on this has gone as quickly as it has. The further the
research goes into smaller and smaller participants in the
ecosystem the further the connections extend (Woods
& Brock; Reid & Woods; Read, Francis, & Finlay,
Perry's articles; etc.).
Generally, plants that grow together support the same group of fungi and suppress together the same pathogen populations. There is a grid on all mycorrhizal sites that interlinks all the plants that are coupled to it. This grid can range from a lichen to the largest trees in a forest to miles of prairie. The mycologists are keying out each species of fungus within this grid. For our purposes in this manual we only need to match plant community and the way the plants fit into the community (Stress-tolerants to Circumventors to Ruderals). Mycorrhizal associations are the foundations of the plant community. Plant the plant within the right plant community as we've described, and the fungal community will also be stable. This fungal-plant intermix spreads the stresses of individual plants among the other plants of the community. The seedlings are supported by the larger well-established plants of the community, as long as the community is intact and the young seedlings match the community. The areas this can include seem to be vast. DNA coding is being perfected, allowing for tracking individual fungi associated with the plants in a community. The largest we've heard of to date is 5,000 acres. We do not see why larger areas will not be found (as our site has the same species of fungus as the Mojave desert.) These influences may not be great over long distances (acres), but may be the difference between a healthy or stressed plant community. We know that each individual plant-fungi unit can have an effect for 50 or more feet within a matter of days. It is possible that water from a river could move up a hillside 200-300 ft. in a week or two via these interconnections.
Hopkins and Chiarrello et. al., etc. found our hillsides all connected with the same fungal species. Read, et. al. found moisture and nutrition movement normal within associated mycorrhizal plants. Plants with the wrong mycorrhiza or no mycorrhiza are excluded. This exclusion can be very strong, killing the new plants by not supporting the formation of mycorrhiza on their roots. The plants never develop a good root system because they have to fight their way out into the miss-matched grid. Think of it as if each plant has a series of keyholes on its roots. If the right mycorrhiza is present its key will fit and immediately allow the root system to draw nutrition and water from the grid. This drawn nutrition may be slight, but from our experiences it allows the new plants to be on an equal level with the established plants. The native ecosystems in California are based upon Cooperation NOT Competition. Native plants cooperate with each other, but they compete against alien plants. This competitive advantage of the members of a native plant community over mismatched plants allows community-based plants to be 'established' within weeks of planting. The mismatched plants can be alien plants or plants that are members of the plant community that were planted in the wrong location. The key to one-watering planting is putting things back as they should be. I prefer to think of the matched sites as mutualistic, all supporting all for the long- term betterment of all. The plant community may be viewed as one entity, like all the organs in a body make up an organism. (*Gaia)* You can't take a heart or liver out and expect it to survive alone. Along those same lines it is very difficult to implant one persons organ in another. The body sees it as foreign and fights it. Lots of drugs are need to suppress the human immune system. This is sort of like all the fertilizer, water, and pesticides needed to maintain an ecologically messed up site.
On the other hand, if the key doesn't fit, the plant has to work off its own meager root system. If the plant matches the grid, you will need no water after the first few waterings (particularly with stress -tolerant ectomycorrhizal plants). If there is no match, you will have to water the plant for years. The mycorrhizal community is driven by the plants in the community, just as the plants in the community are driven by the mycorrhizae. If you view the mycorrhizae as the roots, the roots as the trunk, and the rest of the plant as the leaf and flower you are much closer to environmental reality.
The association of microorganisms that you cannot see is protecting the plant and providing much of the nutrition and moisture for the plant. The plant community matters; the associated microorganisms that make up the whole, matter. You cannot just plant one plant and have life be good. You cannot buy some mycorrhizae and throw the magic potion out and have the weeds turn into native plants. You have to put back as best you can what is supposed to be there. You do not need to be perfect; the key can be sloppy and it will turn. Too far off though, and the plant community engine will not start.
The forest practices in the forest today are destroying the lichens, shrubs, perennials, mycorrhiza, associated microorganisms and, as a result, the trees. This is one reason the forests and deserts are declining from pollution (Arnold and also Allen). Putting a pipe line between a water source and the desert may change vast areas of the desert. We've had customers with plants that had signs of overwatering, that had not been watered for years, but their neighbors a half a block away were watering a sod lawn ten minutes every day. If you live in a wildland interface, it is your responsibility to use the least amount of water, pesticides and fertilizer you can and protect the plant community as much as possible. Your impact may be significant for as far as a mile away.
Consider strongly the interdependence of species and set out plants as close to your plant community as possible. (Look at the declining or dead trees in an old ghost town or abandoned farm to observe what NOT to do.) This interdependence of plants in a particular plant community is the primary reason why it is so difficult to grow forest plants in the desert and the reason why many desert plants struggle when planted in chaparral or forest areas.
What this means in many gardens, whether they be in the wild, or in town, is that your little plants will "plug in" to the plant community of your area (if you have planted correctly). Then the plants already in your yard will help carry the new sprouts on the block until they are established. This is one reason why it is so much easier to plant into a healthy old garden than to plant a stripped site (a new subdivision) or a weedy garden.
Remember
also that most of the mycorrhizae reside in the top 2'-3' of soil
and this interconnected mass of fungi and roots needs mulch (or
annuals that will support the appropriate fungi) to cover the
ground (See pioneer section). Nabhan argues that many desert
plants have to have nurse plants to start because the mycorrhizal
inoculum is lacking without the mother plants that maintain and
provide the ecology until little plants sprout. The effects have
been found with plants as diverse as Saltbush (Atriplex spp.),
Wildflowers and Birch (Betula spp.). The mycorrhizae only grow
through the soil at a rate of 2-5 ft.(75-150 cm.) per year for
ectomycorrhizae and 3 ft.(100 cm.) per year for VAM
(vescicular-arbuscular mycorrhizae). If the fungal community grid
and its associates are out there, they will protect the mother
plants, and provide a giant underground sponge to store nutrients
and water. The fungi makes water and nutrition available to the
plants through extended droughts. Plant-mycorrhizal relationships
have evolved for thousands of years. In good years both reproduce
and expand; in bad years, this relationship is what allows the
plants to survive. Non-mycorrhizal plants put out millions of
seeds, while heavily mycorrhizal plants tend toward long term
survival, with a few seeds produced, but some produced each
decade. Which is better, a plant that survives and shares with its
pals, or a plant that aggressively seeds itself everywhere and
supports pathogens that kill even itself?
On all sites if a few 'mother', 'nurse', 'companion' plants are left on the site when the site is razed, it would allow much of the community to survive, making revegetation much easier, and often make a nearly impossible job possible.
This fungal grid-associated
microorganisms-plant community-animal community relationship is
site-specific, soil and soil-depth specific. Every site has a
slightly different grid made up of different fungi and other
microorganisms as the plant species, climate, and to a much lesser
extent, the soil changes. The plants in each community have
evolved to live with their grid, their type of soil and their
climate. This is a strong argument for planting site-specific
plants only. But Villeneuve
et al. and Widden
(found that the plant community was the main reason for the
existence of the fungal grid. The plants within that community can
have many fungal associates, and they change that association as
they develop and need to adapt to changing conditions. Within the
plant community, the fungi also change their DNA structure to
adapt to change. What this means is that as you put the plants in
the right habitat (community, soil and climate), they can connect
into the grid. It is better to plant the right sub-species, even
if it comes from miles away, than to plant a plant from a
non-compatible plant community although it is only 20 feet away.
This seems so simple but often is lost in the design. The best
example I can think of is where the Southern Oak Woodland
interfaces with the desert. Here, the oaks (Quercus
spp.) are only a few hundred feet from the Joshua Trees (Yucca
brevifolia). The oaks are only found in groves; where an oak
has come up away from the grove, it is small, weak and stressed.
Oaks grow very poorly in the desert as they are not supported by
that plant community. Most mycorrhizal/pathogen associations are
as significant but we cannot see the effects except in poor
growth, disease, browse damage, and poor establishment of the
plants. If the grower is not using fungicides or other pathogen
controls, the gallon root ball should have enough VAM or
ectomycorrhizal inoculum to carry the root system until it
establishes on a site, and can be used to return a damaged site to
a healthier condition.
Further,
many of our native plants have allelopathic tendencies and will
suppress or even kill plants that are not members of their plant
community. The irony of it is, the way the new plant may overcome
the allelopathy is by plugging into the community grid provided by
the allelopathic plant. This is dramatic in chaparral plant
communities. No weeds are present, and only the associated herbs
of the community come up between undisturbed climax plant species.
Pathogens kill the weeds, but leave the native plants alone.
Combine plants of the same communities and you can move through adjacent communities. We've been planting by community for years and have found it to make the designs much nicer looking, easier to install and much easier to design. They 'design' themselves together and take care of themselves; the maintenance is also easier.
The plant communities tend to be mostly one type of mycorrhiza with fingers, or spots of the other mycorrhizas blended in, in the same and different soil levels. The types of plants also tend to be this way. Most perennials are linked to VAM, and the shrubs and trees within a community are usually a continuum between VAM, ectomycorrhizae, or ericoid mycorrhizae. We usually will put spots of color with perennials and transition into trees and shrubs away from them, as the same pattern occurs in plant sizes. If you look at an oak tree it is ectomycorrhizal (or weakly VAM); under it is a plant like Wild Currant or Gooseberry (Ribes spp.) which can be ectomycorrhizal, VAM or non-mycorrhizal (sometimes on the same plant). Under the Gooseberry (and out toward the sun) will be a plant like Buckwheat (Eriogonum spp.) which is VAM that tolerates ectomycorrhizae. Each is connected in its own way. VAM to VAM, and ectomycorrhiza to ectomycorrhiza with Gooseberry as a transition plant in the middle. The same is true in plant communities; Oak is Oak Woodland (Ectomycorrhizal +weakly VAM), Buckwheat is Chaparral (VAM) and Gooseberry is in both plant communities. The same occurs with plant strategies. Stress tolerant plants are commonly the trees or large bushes, Circumventer plants are the decicuous shrubs, groundcovers and perennials, and ruderal plants are the usually short-lived water -loving perennials and annuals. As succession occurs, a plant community normally moves from R (ruderal) to S (stress tolerant).
Hey, don't worry so much, just plant back what was supposed to be there and all this will happen naturally!
In one part of our demonstration garden we've lost a lot of desert plants to drought, but the chaparral plants grow like weeds. Our plant community in that area was Chaparral/Oak Woodland and desert plants were poorly supported. We moved the desert plants out into the Chaparral/Grassland and now they're doing fine.
Generally, matching the plant community is safer than matching mycorrhizal type. If you can tell which specific mycorrhizae are associated with your plant, match that within the right community. If the plants are grown in a seasonal climate that is as bad or worse than yours you will generally have mycorrhizal matches. That is, within a mycorrhizal species (such as Glomus mosseae) there are variants that do well only in easy sites, such as our cool coastal fog belt; inland, these mycorrhizae will not be viable (Stahl, et. al.). You can go from the harsh site to the easy, though, because a seasonal association will match. Mycorrhizal types change as the seasons and moisture levels change. The best way to describe this is as follows: a tree may support many types of birds, each helping the tree as it is living off of the tree. Hummingbirds may appear in the early spring to pollinate the flowers, at the same time feeding on the nectar in the flowers. Nuthatches may nest in the tree in the spring, eating insects living on the tree. Thrashers may nest lower in the tree, scratching in the leaf litter for bugs. Jays may eat the fruit still later, spreading and planting the seeds all over the place as they fly away with their prizes or hide them for latter. All are benefiting from the tree, but at the same time the tree is benefiting from them. The same occurs with the fungal and other microorganism companions. They will interact with the tree during different seasons, never moving away, but not constantly interacting all year. Sometimes, not the same type of fungus will be active or sometimes the companion bacteria will 'kick in', depending upon environmental conditions.
Part of the challenge is learning not just which are VAM and which are ectomycorrhiza, etc., but learning which are not antagonizing each other. Alders (Alnus spp.), for example, can be either ectomycorrhizal or VAM, but they match only 4 out of 28 species of ectomycorrhizae tried by one author and 3 out of 9 by another. From our plantings it appears some species of one type of mycorrhiza, needed by some plants, cannot survive well in areas where other types of mycorrhizae are present. That is, some mycorrhiza and/or plants will not tolerate non-native (to the site) types. Mycorrhizal potions you can buy often make the plant and the plant community weaker, not stronger. For most mainline installations you need only match plant communities. Using communities that are next to your target are acceptable if the plants move through the site as they do in the wild. If you want to use plants from other areas, put the plants in those communities together in a spot as close as you can get to that community in the wild. For difficult sites we do consultation. For most landscapes, just get as close as you can.
.."science is rife with error. Because so many people are so thoroughly schooled in the common misconceptions, however, only the most brilliantly skeptical of them will ever discover a mistake. And even then, it will likely be denied for generations to come. If the error has cultural importance too--such as the belief that emotions arise from the heart-- generations stretch into centuries." Marilyn Vos Savant, Parade Magazine, Feb. 6,1994
I think one problem people have with plants and ecology is that they cannot think long-term. Most California native plants and stress tolerant plants have long-term strategies for survival. For perennials and shrubs a lifetime of 100+ years is common. For example, Creosote (Larrea tridentata) lives 15,000 years. For trees a lifespan of 500+ years is common. The Coast Live Oak (Quercus agrifolia) trees around the nursery probably germinated during the wet periods in 1630, or 1680 (we counted the annual rings on some fallen branches). In contrast, the weedy ruderals that people plant in their yards live for only a year or two.
We normally do not see a major turn in an ecosystem, or a plant in that ecosystem for at least 10-20 years. Trappe talks about some mycorrhizal types of fungus not appearing on sites for 20-25 years.
Why
should a tree or fungus with an 8-800 times longer lifespan than
ours respond instantly to our actions?
In a conventional garden with access to regular water, knowing your plant communities can reduce your problems with insects and weeds. You can modify the extreme measures we use in a restoration and combine plants of the same type communities throughout the world. The chaparral plants from around the world combine well as long as the rainfall needs are met with supplemental spring water. The forest trees can be combined in a similar manner as long as the conifers are together and the VAM- type trees are together. A desert garden can be a combination also. These all work easier though if the plants from S. Africa are planted in one clump and the ones from Chile in another, the ones from Quebec are in one forest clump and the ones from Europe are another, etc., etc. Remember, you will have problems with this scenario, but less than in a conventional garden.
REMEMBER TO KEEP THE RUDERAL plants AWAY FROM THE STRESS- TOLERANT plants with the Circumventer plants as the buffers.