Redwood Reader

Study shows trees absorb 60% more rain than pasture
This came from Rainwaterharvesting yahoogroup, reprinted from the Guardian. Several things really stand out in this relevant to our discussion about glomalin and retention of precipitation in watersheds: The farmers could SEE the difference between the forest and pasture runoff, 2.. They wanted to make sure they performed sound science 3. The unexpected jump in water absorption and all the biological benefits there from, 4.Reduced flooding likely because more water is absorbed in the watershed, 5. Water retained in the watershed is available over longer periods of time in dry times. They do not claim to know why this is, but glomalin conditioning the soil for extended periods in conjunction with erosion mollifying effects of the canopy, we find our concept being carried out. Substitution of wood chips for straw is significant as it is a byproduct of forest management rather than from cleared land. It would be good to know if the pasture was annual grass without mycorhizzia or perennial grass with fungal associates, as perennial grasses do condition the soil to absorb water. The difference between perennial grasses and forest then is a matter of time and growth rather having and not having glomalin producing fungi.

Trees hold answer to floods menace
Robin McKie, science editor Sunday September 26, 2004
The Observer http://www.guardian.co.uk/weather/Story/0,2763,1313067,00.html
http://forests.org/articles/reader.asp?linkid=35229
Scientists have discovered that simple strips of newly planted woodland could play a crucial role in halting the floods that have devastated British towns in recent years. They found that land with trees can hold vast amounts of water that would otherwise stream down hills and surge along rivers into towns.
'The extent of water absorption was entirely unexpected,' said Dr Zoe Carroll of the Centre for Ecology and Hydrology in Bangor. 'It also has great potential for helping us deal with floods.'
Scientists at the centre collaborated with farmers from Pontbren, a community in the North Powys hills. Several years ago farmers there decided to reduce the intensity of land use, which had seen a sixfold rise in the number of animals grazing there since the 1980s.
'The system just wasn't working. We were on a treadmill, working harder, producing more but earning less. We set about changing the way we farmed to rely more on what the land could produce,' said Roger Jukes, a farm owner.
The farmers began to stock hardier sheep which needed less tending. They cut back on grazing land, planted more trees to provide shelter for the animals, used woodchip instead of straw, and made the land more ecologically friendly. Owls, voles and shrews began to appear at the farms.
'It has been great to see so much wildlife returning to the farms,' said Jukes.
The project started with three farms. Today there are 10, covering more than 1,000 hectares of verdant Welsh hillside. But the farmers wanted more than an improved lifestyle - they wanted their efforts put on a scientific footing. They had noticed that during rainstorms their newly planted woodland seemed capable of absorbing vast quantities of water while grazed land let rain pour down hillsides. So they invited the scientists to study the land.
'We measured rain that was being absorbed by grazing land and by woodland, and found the latter was 60 times more effective at taking up water than soil on land grazed by animals,' said Carroll. 'We expected to find a difference, but not one of this magnitude.'
The team do not fully understand the reasons for this, though grazed land tends to be compacted by hooves and this could reduce its capacity to let in rain. Trees also generate roots that break up soil, creating pathways for water to move through.
Regardless of the cause, it is clear the discovery could have great practical implications. In 2002 flooding triggered by rainwater pouring from hillsides caused millions of pounds of damage to Shrewsbury, while Kidlington in Oxfordshire, Peterborough in Cambridgeshire and Leamington Spa in Warwickshire were all badly flooded in 1998. Scientists say that flooding is destined to get worse as global warming increases climate instability.
But the Pontbren research suggests a way to counter this problem. 'By planting trees on strategic plots we could create areas to soak up rain, allowing it to move into the soil rather than flowing over the land,' said Carroll.
'Water will always move down a hill, either over the surface or through the soil, but this way we could stop it all arriving at the same time. Major surges would merely become heavy flows.'
A £6m research programme is now investigating Britain's flood problem and will focus on Pontbren.
Hydrologist Professor Howard Wheater of Imperial College London said: 'Pontbren and the work done there is going to be very important in working out ways to halt major floods. We still have a lot of research to do, but tree-planting looks like having a significant role to play.'