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Secrets of the Underground Network

by Neil Anderson

This is a close-up of the "famous" Big Sur revegetation site.

Good coffee, front wheel drive, two sided photocopies, Velcro, electricity, the round earth. It has been said that Genius is the art of seeing the obvious. Many inventions or discoveries that we take for granted as part of our lives do indeed seem obvious, although for thousands of years they eluded the grasp of mankind.

Mycorrhiza are part of the living soil that have been oft discussed in the pages of popular magazines such as Land and Water but remains relatively unknown in practice to many in the restoration industry. Like the round earth, mycorrhizal inoculation is an idea that was once heretical and will soon become an obvious part of our lives and practices. When soil is heavily disturbed; trampled, compacted, fumigated, stockpiled for a long time or subsoil is used as in mine reclamation and road cuts, many local plants do not grow well. Suddenly, good plants fail to thrive and bad ones we often call weeds prosper. In such cases, clearly the soil is different. If soil was just a source of nutrients and water, then all one would have to do is add enough of them (possibly quite an expensive proposition) and a stable cover of good, native plants would grow. If only life were so easy.

We know that good plants, now often meant to be lower maintenance native vegetation or at least plants that are not "weedy" or invasive by nature, often have a hard time coming back to our difficult, disturbed sites. We put the seeds of our target species back on site because we do not wish to leave things to chance and time. Time, after all, is money and we need to get on to the next job. It seems obvious that our desirable plants will take more time to come back to our site than we would like and, that they in fact, may not come back at all because of crowding out by those ubiquitous dastards we call "weeds." What is not obvious is that there might be something missing from the soil that limits the ability of the "good" plants to come back, that this "missing link" might be biological, and it may also take much longer to comeback on it's own than we would like. The first recognition of mycorrhizae's importance came when Pine trees from the mountain west were planted in some distant land. The seedlings would not grow. When soil from the original areas was added to the soil of the seedlings, Presto!, the seedlings began to flourish.

Within the tyranny of time lies the conflict that exists regarding native plant revegetation and the use of mycorrhiza. Mycorrhiza will comeback on their own but it will take time - two to three years based on the science of mine reclamation and their stockpiles of dirt. In these two or three years, weeds may takeover the site and native plants perform poorly without their natural mycorrhizae. Just as we replace seed, advocates of mycorrhiza say we can reseed with the spores or "propagules" of mycorrhiza to improve the establishment of native species.

The problem with the weather, Mark Twain said, is that everybody talks about it but nobody does much about it. The same may be said about mycorrhiza. Mycorrhizae (mycorrhizae is plural) have been studied extensively by scientists for up to a century. We know what they are, what they do and we have the data to prove it. Mycorrhizae increase a plants' root system and allow them to grow with less fertilizer and water. In harsh conditions, like a roadside restoration or a mine site, mycorrhiza may mean the difference between success or failure. Additionally, mycorrhizae have also been shown to produce a gluey substance that improves soil structure and infiltration. The USDA has published an article called Glomalin - manageable soil glue that states, "higher levels of glomalin give greater water infiltration, permeability to air, better root development… resistance to surface sealing and erosion." Research by the Minnesota DOT and the Federal Highway Administration demonstrated a 77% increase in native prairie grass cover in the second year; this is similar to one of the original CalTrans studies that showed a 70% increase in native plant cover with the ENDOmycorrhizal inoculant. The VAM or ENDO mycorrhiza in most commercial inoculants has been shown to be important for plants in regions as diverse as the high plains, the prairies, as well as Hardwood forests and California's coast.

There is a whole web site with searchable databases dedicated to mycorrhiza by the University of Tennessee; (http://mycorrhiza.ag.utk.edu/).

Munsell McPhillips, an urban stream design and restoration specialist for Intuition and Logic in Webster Groves, Missouri, states "when you work with urban corridors, plants endure tremendous stress. I heard about mycorrhiza and researched it and thought, man this makes sense, dealing with our soils which are mostly sterile fill." McPhillips explains that they design projects that include vegetation ranging from Willows and Dogwoods to upland grasses and trees such as Oaks and Hickories. Mycorrhizae were applied through a root dip. " We tested four different sites, all in the same soil and noticed tremendous vigor in plants compared to some adjacent sites that were not treated."

Scientists write that up to 10 or more species of mycorrhiza can be found living on a plant's roots at any one time, that mycorrhiza will associate with many different plant species, and that a few species of mycorrhiza occur across North America and parts of Europe with little if any detectable genetic variation. The conclusion is that mycorrhizae don't crowd out or take over against other species, so adding mycorrhizae won't stop other native strains from establishing on your site. Adding mycorrhiza is a way to get things off to a good start and speed up the revegetation process.

"People ask me about mycorrhiza all the time, they definitely are starting to create a buzz. However, beyond all the data, practitioners want to know who they know who has added or inoculated with mycorrhiza," explains Shannon Peters of Sacramento, CA's Mycorrhiza Labs, Inc.

Bruce Berlin of California's S & S Seeds adds " Many of our customers have had great success with mycorrhizal inoculum and it is specified by CalTrans based on several years of their evaluation. A lot of contractors don't have time however, to go back and sample their projects, so they often can't tell you exactly how well it worked. We, as an industry, have not taken the time to develop and provide the numerous case studies and evidence that mycorrhiza does in fact work well as a revegetation tool. Mostly, the success stories have been shared anecdotally with a few practitioners. We need to take the time to get the side by side pictures and supply the evidence that mycorrhiza is a great form of insurance."

Dr. Mike Amaranthus studied mycorrhiza for 20 years for the US Forest Service in Oregon and now runs his own business consulting about mycorrhiza. "Close to 90% of the forestry seedlings produced in the U.S are inoculated with ectomycorrhizae which are the mycorrhizae that benefit most conifers. We are seeing tremendous interest in landscaping nurseries and in restoration for the endomycorrhizae that benefits grasses, shrubs and hardwoods." Dr. Amaranthus concedes that the market took many years to develop and is limited by the OMBY phenomenon, Only in My BackYard. "Many people hear about good results from contractors for CalTrans and then ask ‘well, what about in Oregon', so we have had to perform a lot of education and trials."

Stephen Gruman, a biologist for RTI, a commercial producer of endomycorrhizal inoculum adds " we try to represent mycorrhizae scientifically but many contractors don't have time to do the science and yet still are skeptical since I wear a sales hat. Perhaps a bigger challenge is that it takes landscape architects and the bureaucracies they work in a while to change. Certainly it is hard for both the contractors and Landscape architects to get out into the field together. I have given away a lot of material for trials but in too many cases there was a lack of follow up." Gruman continues," for some contractors who have done the follow-up, mycorrhizal inoculum can be a secret advantage. Nakae and Associates, a large design and build restoration contractor in Southern California and Salt Lake City, uses mycorrhiza every year."

This is the Big Sur site - the circled area is where the site was seeded with an amendment package which included compost, enhanced biosolids and mycorrhizal inoculum.

Shannon Peters' Mycorrhiza Labs, Inc. is an independent offshoot of the producer RTI in response to the need for more data and monitoring of sites treated with mycorrhiza. Peters has begun consulting and monitoring the results of revegetation projects throughout the country. One such project has been on California's scenic but steep Big Sur Highway, (Land and Water, Nov/Dec. 2000). "Results with native grasses and mycorrhizal inoculant were excellent. The site was superior to an older, neighboring site that wasn't inoculated. We are definitely seeing the associations occurring between mycorrhiza and target plants on treated sites." Peters has been able to analyze soil organic matter levels, mycorrhizal colonization and vegetative cover. "While the Big Sur Site was not set up as an experimental trial, it is an excellent opportunity to link measurable characteristics to an obvious success. The lack of post-construction monitoring creates a void of extremely valuable information to what makes a site a success or failure. Monitoring sites like Big Sur offers us a chance to establish a database with which to evaluate future projects and to hopefully start to give meaningful recommendations based on quantitative data," states Peters. Peters can also analyze soil for the quantity and even species of mycorrhiza before any treatment is recommended. Experimental trials are happening throughout the country. In some cases she has recommended to people not to use mycorrhiza or has developed a more inexpensive way to treat and improve the site.

Early results like this with mycorrhizae, while promising, lacked monitoring and data.

Unfounded claims and a lack of hard evidence have often contributed to a reasonable lack of practitioner confidence in the need and usefulness of mycorrhizal inoculant in the past. However, the new approaches to monitoring and measuring initiated by companies like RTI will undoubtedly give credence to the use of mycorrhizal inoculant as a key portion of a complete restoration program. Inoculum users will benefit from the research and innovation as producers find ways to optimize inoculant use and success through appropriate measuring and monitoring of field sites. The time may come where all our restoration sites are as successful and scenic as the Big Sur Highway. L&W

For more information contact Neil Anderson, RTI, 1341 Dayton Street, Unit G, Salinas, CA 93901, (800)784-4769, fax (831)424-1495, www.reforest.com.

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Friday, November 22, 2002 - http://www.landandwater.com/features/vol46no4/vol46no5_2.html