L
Luther Burbank
Mobo, we've been round this track before, but all the evidence I've seen indicates the vast majority of fixed N goes straight to the cover crop and only truly joins the soil when the plant decomposes.
Published on Jul 29, 2012
In this real-life model of forest resilience and regeneration, Professor Suzanne Simard shows that all trees in a forest ecosystem are interconnected, with the largest, oldest, "mother trees" serving as hubs. The underground exchange of nutrients increases the survival of younger trees linked into the network of old trees. Amazingly, we find that in a forest, 1+1 equals more than 2.
Suzanne W. Simard - Faculty Profile (live link with tons more info/links)
Dr. Suzanne Simard is a professor with the UBC Faculty of Forestry, where she lectures on and researches the role of mycorrhizae and mycorrhizal networks in tree species migrations with climate change disturbance. Networks of mycorrhizal fungal mycelium have recently been discovered by Professor Suzanne Simard and her graduate students to connect the roots of trees and facilitate the sharing of resources in Douglas-fir forests of interior British Columbia, thereby bolstering their resilience against disturbance or stress and facilitating the establishment of new regeneration.
Dr. Simard writes:
Mycorrhizal fungi form obligate symbioses with trees, where the tree supplies the fungus with carbohydrate energy in return for water and nutrients the fungal mycelia gather from the soil; mycorrhizal networks form when mycelia connect the roots of two or more plants of the same or different species. Graduate student Kevin Beiler has uncovered the extent and architecture of this network through the use of new molecular tools that can distinguish the DNA of one fungal individual from another, or of one tree's roots from another. He has found that all trees in dry interior Douglas-fir (Pseudotsuga menziesii var. glauca) forests are interconnected, with the largest, oldest trees serving as hubs, much like the hub of a spoked wheel, where younger trees establish within the mycorrhizal network of the old trees. Through careful experimentation, recent graduate Francois Teste determined that survival of these establishing trees was greatly enhanced when they were linked into the network of the old trees.Through the use of stable isotope tracers, he and Amanda Schoonmaker, a recent undergraduate student in Forestry, found that increased survival was associated with belowground transfer of carbon, nitrogen and water from the old trees. This research provides strong evidence that maintaining forest resilience is dependent on conserving mycorrhizal links, and that removal of hub trees could unravel the network and compromise regenerative capacity of the forests.
In wetter, mixed-species interior Douglas-fir forests, graduate student Brendan Twieg also used molecular tools to discover that Douglas-fir and paper birch (Betula papyrifera) trees can be linked together by species-rich mycorrhizal networks. We found that the mycorrhizal network serves as a belowground pathway for transfer of carbon from the nutrient-rich deciduous trees to nearby regenerating Douglas-fir seedlings. Moreover, we found that carbon transfer was enhanced when Douglas-fir seedlings were shaded in mid-summer, providing a subsidy that may be important in Douglas-fir survival and growth, thus helping maintain a mixed forest community during early succession. This is not a one-way subsidy, however; graduate Leanne Philip discovered that Douglas-fir supported their birch neighbours in the spring and fall by sending back some of this carbon when the birch was leafless. This back-and-forth flux of resources according to need may be one process that maintains forest diversity and stability.
Mycorrhizal networks may be critical in helping forest ecosystems deal with climate change. Maintaining the biological webs that stabilize forests may help conserve genetic resources for future tree migrations, ensure that forest carbon stocks remain intact on the landscape, and conserve species diversity. UBC graduate student Marcus Bingham is finding that maintaining mycorrhizal webs may be more important for the regeneration and stability of the dry than wet interior Douglas-fir forests, where resources are more limited and climate change is expected to have greater impacts. Helping the landscape adapt to climate change will require more than keeping existing forests intact, however. Many scientists are concerned that species will need to migrate at a profoundly more rapid rate than they have in the past, and that humans can facilitate this migration by planting tree species adapted to warm climates in new areas. UBC graduate student Brendan Twieg is starting new research to help us understand whether the presence of appropriate mycorrhizal symbionts in foreign soils may limit the success of tree migrations, and if so, to help us design practices that increase our success at facilitating changes in these forests.
Mycorrhizal Networks: Common Goods of Plants Shared under Unequal Terms of Trade1
Abstract
Plants commonly live in a symbiotic association with arbuscular mycorrhizal fungi (AMF). They invest photosynthetic products to feed their fungal partners, which, in return, provide mineral nutrients foraged in the soil by their intricate hyphal networks. Intriguingly, AMF can link neighboring plants, forming common mycorrhizal networks (CMNs).
What are the terms of trade in such CMNs between plants and their shared fungal partners?
To address this question, we set up microcosms containing a pair of test plants, interlinked by a CMN of Glomus intraradices or Glomus mosseae. The plants were flax (Linum usitatissimum; a C3 plant) and sorghum (Sorghum bicolor; a C4 plant), which display distinctly different 13C/12C isotope compositions. This allowed us to differentially assess the carbon investment of the two plants into the CMN through stable isotope tracing.
In parallel, we determined the plants’ “return of investment” (i.e. the acquisition of nutrients via CMN) using 15N and 33P as tracers. Depending on the AMF species, we found a strong asymmetry in the terms of trade: flax invested little carbon but gained up to 94% of the nitrogen and phosphorus provided by the CMN, which highly facilitated growth, whereas the neighboring sorghum invested massive amounts of carbon with little return but was barely affected in growth. Overall biomass production in the mixed culture surpassed the mean of the two monocultures. Thus, CMNs may contribute to interplant facilitation and the productivity boosts often found with intercropping compared with conventional monocropping.
IMO living mulch is over hyped, and only good for the worm bin...which makes it dead mulch. Good soil already has microbes, and doesn't need N fixing. I'm loving rice hulls for mulch.
Diverse generously top dressed EWC will be plenty active when moist. Straw, leaves, bark, whatever is all I think is needed. I've done three runs with white Dutch, red, and mini clover. Thought it just looked cool, and see no diff without it.
Could you share your thoughts and experiences on this? I'm on the same boat though, if nothing else it will look cooler than a big expanse of dirt. I can't see how it will hurt anything and I'm really looking forward to seeing what this can do for my ladies.
Going to top dress some EWC and kashi under aluminum foil. I've never seen roots reach for the top.
Good discussion. I gotta ask, what is the best mulch (top dressing) for retaining moisture?
Here's why I ask, it's very hot in my micro, I use ventilation to remove the most of the heat but it takes the moisture with it. I use Sunshine mix and feed teas into 2 gallon pots every 5 waterings*. At issue is that I often have to water every other day. So I'm watering 3-4 times a week and feeding once every 8-10 days. Currently I use no top dressing. I would like to extend the intervals between watering.
So what would you folks recommend, please don't recommend larger pots, I haven't room for larger pots, nor do I have the option of utilizing a drip system?
Thanks for the advice. I just did a short search and found it for 20$ a pound, kinda pricey. I live in cow country, I guess I should just stop and visit the farmer next door, I'll ask if he has any or if he knows where to get it locally.Barley straw and leaves (from your cannabis plants) Mostly any plant matter topdressed on your soil will help retain moisture as they decompose onto your soil surface.
Thanks for the advice. I just did a short search and found it for 20$ a pound, kinda pricey. I live in cow country, I guess I should just stop and visit the farmer next door, I'll ask if he has any or if he knows where to get it locally.