Redwood Reader

3. Our Shrinking Watershed
One of the exciting things about todays world is learning of scientific discovery you can see with your own eyes. Trying to understand and repair a heavily damaged creek bottom property has led to many fields of inquiry, such as where is water stored in the ground if there are no aquifers; how do you stop, prevent or repair slides, what causes some trees to grow faster than others, and can I help global climate change by doing so? Aspects of the science involved have changed markedly in the last twenty-five years even if those facts seem slow in reaching us or shaping policy or techniques. It was twenty-five years ago Dan Largeant of USFS in McKinleyville first began inoculating Douglas fir seedlings with mycorhizzial fungi for faster growth and higher survival rates. The 1996 discovery of glomalin by Sara Wright and Kristi Nichols of USDA keys the understanding of soil carbon storage and by extension soil moisture retention, as well as providing insight to stored carbon loss through land uses and climate protection through increased soil storage via managed vegetation practices on farm, field and forest. While a ton has been learned about these fungi and their role and value in our watershed and the global environment, it is only slowly trickling down to the common folks.
Prisitine watersheds shed little runoff as part of their natural process. Almost all the precipitation is intercepted, slowed down, diffused by branches, leaves, stems and duff and slowly absorbed into the water carrying root zone soils. Measured from headwall to headwall and source to outlet, there is not much that can change the total area of a watershed. Runoff is usually measured by the amount of rainfall in a given area, less a fixed amount for absorption and biological retention. Both of these are challengeable in the light of better science. For example, absorption IS biologically induced. Vast amounts of carbon are stored in the soil of undisturbed lands, in these areas our wilderness values prevail even as we are unaware of the unity of the forest as a system.
Conditions above ground are clearly not what they once were. If we think of a watershed in three dimensions we begin to see the extent of the problem. From the canopy to the tips of the roots lies the total plant precipitation interface zone. We can divide the picture into halves, above ground the trees intercept the precipitation, whether rain, snow or fog mist. Below ground they create water storage in soil by fungal production of glomalin from carbon products produced by the tree. Both are influenced by the local climate, in turn impacting the watersheds’ water carrying capacity reducing the watersheds ability to modify weather.
Above ground, we have reduced forest canopy drastically in cut areas. Less shaded air is conditioned in the summer, raising air temperatures and the moisture carrying capacity of the air, leading in turn to excess summer drying and earlier dates for once-perennial streams drying up, and higher fire danger. Fog mist gathered by needles no longer reaches 300’ in the air. Less rainfall is slowed and used by the trees or stored in the soil, leading to more erosion. Rain pelts exposed soils creating running water-enemy of all watersheds. Second growth takes advantage of the extra sunlight and water available but is not mature enough to handle the large historic rain events that determine local conditions. Tree growth fills in the canopy rapidly seeking sunlight to fix the CO2 into carbohydrates which are sent to the roots, as the tree must provide good living conditions and nutrition for the fungi it needs to thrive. Fungi’s enemies are sunlight, ambient air and running water, and so the tree closes the canopy, covers the ground with duff, penetrates the soil together with the fungi in search of water and minerals, and feeds the fungi through extra sugar products from photosynthesis. Elevated CO2 also has been shown to result in smaller stoma size in leaves and needles, lowering the overall transpiration rate, and again retaining water in the immediate environment.
Soil water repellency is an increasing problem in many area and many uses of the land. In almost every case the land has been disturbed, its original water balance ignored or forgotten, natures method of retention and restoration is unseen and unknown, and the overall effect is a gradual drying of the entire ecosystem, increased runoff and erosion, again leading to CO2 soil losses and the old adage “In mans footsteps-the desert.” Increased CO2 has been shown to reduce the water repellency of soils in a variety of settings. The well understood restoration principle of revegetation returning flowing creeks is due to the increased saturation zone. Methods and conditions that retain surface water for percolation into the ground like recharge ponds allow overwhelmed root zones to use the water a little later, prolonging saturation and decreasing runoff.
Below ground, roots and mycorhizzal fungi condition the soil by binding soil particles into aggregates full of pores for water and air in soils previously without texture. Associated by infection of the root hairs of plants, these fungi seek out minerals in a sprawling network that connects individuals and species and has built in redundancy with many hosts, often two primary dominant canopy species together with local shrubs, forbs and ferns. The leaves and needles create carbohydrates through photosynthesis that are exuded through the roots as nutrition for the fungi. Each year the root tips grow a little further into the soil, conditioning it by depositing glomalin, a newly discovered forest fungi product, renewing areas repeatedly with successive types of fungi and creating a larger water storage capacity. Root tips grow exponentially faster in raised CO2 testing, showing plants take advantage of increased CO2 levels by increasing root storage, even faster than shoots and leaves. So this bodes well for restoration land managers trying to rebalance precipitation and vegetation-higher CO2 levels speed up the growth of forest systems. The constant release of CO2 from land disturbance might greatly effect global CO2 concentration equations, but offer a relatively easy savings in atmospheric accumulations via less damaging land use practices and an eye on development. A little bit of knowledge can go a long way.
The many species of fungi associated with individual tree species as well as their appearance at different stages of the forests condition mean hyphae continually re-infect the soil they live in producing and accumulating large reserves of glomalin. Old glomalin retains its soil binding and conditioning ability over decades, creating large reservoirs of water holding soil in the root zone, and decreasing runoff, erosion and flooding. The water percolates through the conditioned soil slowly, allowing streams to run months after the last rain. The watershed grows in volume above and below ground level via biological activity, increasing the interception of precipitation and its direction and modification and underground storage through the rhizosphere, even as the surface area for absorption is steadily decreased by building, pavement, soil compaction, annual as opposed to perennial grasslands and drainage.
Development and land use practices have decreased the watersheds ability to handle precipitation before it becomes runoff, at which point it is no longer an asset in the watershed. It can only create destruction until it joins a larger body of water. We have made this worse by focusing on draining the land for agriculture, development and in road building. We now have runoff even in very small events were once it took massive rainfall to overwhelm the storage capacity of the soil. Runoff is always a problem on steep ground, almost always creating some kind of disturbance to the ground between its source and its target outlet. Runoff increases as water conditioning land use decreases, and as the soils ability to store water is diminished and destabilized.
Forests should drip and be moist year round. Old growth accumulation of carbon-conditioned soil over hundreds or thousands of years has been totally overlooked as an integral part of forest and watershed management, as has its role in manufacturing and protecting the conditioned soil. No one has quantified glomalin in the redwoods yet that I know of but carbon storage is likely huge- one estimate says five times the carbon is stored in the soil as is contained in the wood of mature trees. It would also appear that the growth stage of a tree, originally considered the greatest carbon using stage, stores less carbon for soil conditioning because it is making wood and leaves Lack of measurable growth was the excuse for converting old growth areas to second growth- the land was being wasted because trees weren’t growing at a rate Wall Street could understand such as board-feet, basal-volume or tonnage. With a figure like 35% of annual carbon production stored in the soil and another figure of 22-45 pounds of carbon per tree per year, we can market these carbon reserves while protecting watersheds through light-handed management. The Carbon Credit Exchange set up in Chicago currently prices CO2 credits at $1.00 per ton. 2000/25lbs=80 trees per acre per year. Rate of storage by various sized trees will need to be determined for a full exploitation of this science. Nevertheless, direct payment to land managers from businesses seems likely and a great way for public agencies to take in additional revenue and as an incentive to public and private landowners.
The science is in- clear cutting is far more biologically detrimental to a forest than previously believed. 85% of soil stored carbon returns to the atmosphere as CO2 when glomalin is destroyed by light, water or air when the soil is disturbed. The difference between cutting stump sprouting species that retain their storage systems, or parts of them, compared to total destruction as in Douglas fir forest shows the need for different forest practice rules by predominant species. The need to retain canopy and undisturbed soils in harvested areas go hand in hand. Implications are enormous- rising CO2 may be more about land development than industrial emissions. Rising CO2 also greatly stimulates glomalin formation in many plant species, giving hope that much past destruction is biologically manageable. . However, elevated CO2 had no impact on available nitrogen or litter breakdown in several studies. Understanding of soil capacity improvement should make restoration of many watersheds a reality with an adjustment of understanding the primary obligation. We have to repair the storage capacity of the landscape by managing vegetation and reducing soil disturbance.
The molecule itself is a wonder and may lead to new commercial products, processes and other innovations by means of harvesting or synthesizing. Fossil fuel formation may have to be rethought. It is under study at the USDA especially for field crops, leading to new recognition of soil saving practices as no-till farming. Unfortunately, the alternative scenario played out in one-third of US cropland is to use pesticide resistant strains of GMO’s together with herbicide treatment rather than cultivation. This does make cropland a carbon sink, as demonstrated in a Rodale Press experiment with organic no-till practices. New understanding about our natural world will lead us into profitable innovation in a far less destructive manner.
At last we know what lies at the heart of old-growth forests, why they are cool and moist in the heat, gently misty and drippy in the rain, why the springs have water for the stream below all year. We begin to have a light on the numbers and specific properties of the many soil inhabitants that make our forests. We finally have a usable restoration goal for water and a carbon storage measuring stick and a captured carbon preservation outlook on land management practices. And by pointing out how much work there is to do, we have created jobs, fields of discovery and possibly new industries.


Atmospheric CO2 Enrichment Reduces Water Repellency of Soil, CO2 Science Magazine: Ref. Newton, P.C.D., Carran, R.A. and Lawrence, E.J. 2003. Reduced water repellency of a grassland soil under elevated atmospheric CO2. Global Change Biology 10: 1-4.
Glomalin: Hiding Place for a Third of the World's Stored Soil Carbon; Sara F. Wright and Kristine A. Nichols are with the USDA-ARS Sustainable Agricultural Systems Laboratory, Bldg. 001, 10300 Baltimore Ave., Beltsville, MD 20705; phone (301) 504-8156 [Wright], (301) 504-6977 [Nichols], fax (301) 504-8370. Agricultural Research magazine , September 2002, part of Soil Resource Management, an ARS National Program (#202) described on the World Wide Web at http://www.nps.ars.usda.gov.
Stomatal Frequency Responses of Conifer Needles to Atmospheric CO2 Enrichment, CO2 Science magazine, Kouwenberg, L.L.R., McElwain, J.C., Kurschner, W.M., Wagner, F., Beerling, D.J., Mayle, F.E. and Visscher, H. 2003. Stomatal frequency adjustment of four conifer species to historical changes in atmospheric CO2. American Journal of Botany 90: 610-619.

http://www.co2science.org
http://www.chesco.com/~treeman/SHIGO/RHIZO.html


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www.ars.usda.gov/is/pr/2003/030205.htm
www.ars.usda.gov/is/AR/archive/sep02/soil0902.htm http://www.crumbtrail.org/mt/archives/2003_10.html