Our Shrinking Watershed

Rich McGuiness armich at cox.net
Sat Apr 10 01:25:00 EST 2004


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
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



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