I have been getting double messages about the benefits/problems with trees as a source of water retention.

On one hand is the arguement that volumns of water are extracted from the ground water and released in the air, thus drying the ground.

On the other hand, and my own experience, is the arguement that trees provide shade, thus cooling the ground and restricting evaporation.

I have seen the results of clear-cutting forests. The ground dries out, ferns die, rhododendrons die, moss' die.....and then when it does rain the water runs off instead of being retained by natural vegetation.

What are your thoughts?

Trees are a much more vibrant source of water protection than a destroyer of H2O. The evaporation and temp warming problem far out weighs the counter point of water needs by tree specie. Given the tree specie in question is well suited, adapted and native to the locality.

And, furthermore, some tree specie, depending upon geography are appropriate users of the water of their birth-thereby not constraining the needs of the stream in question.

Case in point: A good example could be made from the Rocky Mountain Juniper. This particular tree is extremely drought tollerant and requires only small amounts of water to live very happily. Many Eastern WA & OR regions with plateau arid environments are lined with this tree specie at the near shore waters along with other specie such as Ponderosa Pine, Quaking Aspen, Rosier Dogwood, Water Paper Birch, specie of Willow and Black Cottonwood. The latter of these specie require good healthy amounts moisture inorder to survive.

But that's the magic! These "native" specie have adapted over time to extrude water at an amount fitting to the stream/reparian area that they can survive by through natural selection. If a drought strikes and these trees extrude more than the stream can handle, then as a result through natural processes "some" of the trees will eventually die off(through drought, disease, beavers, beetles/insects -etc..) thereby balancing and offsetting the equation. (-This may take continual years of drought etc. mind you) To make an analogy, think of it like elk herd numbers/fawn rates and how they might correlate with a wolf population. In the long-run the other as acts as a counter balance on the "other". The same analogy could be drawn up from cougar and deer populations.

So, the point I'm trying to make is no matter what region you speak of, given natural processes things will and do balance over time.

-->The trick lyes in how we as people interupt/degrade or assist and/or differ these processes at work. By planting "hybrid" specie of poplar for paper production such as the ones found on Boise Cascade land near Tri-Cities we have in a sense, altered the method and natural rythm of water extraction by a tree specie. (From the Columbia R. -not "as" effected due to it's volume) These poplars were developed for the sole purpose of rapid growth(10-15ft a year!! -hard to believe but true) and faster production time to the paper mill. Of course the other gain being easier paper production with minimal damage to the old growth forests and other timber resources etc. at large...

And if we plant a tree specie at a rate and with of a specie of non-nativity, yes sometimes it can constrane the environment in which it lives, burdening it over time. Make sense? I hope?!

(I have worked along side many good foresters over the last 10 years - that's my .02cents!)

Yes, trees can do wonders for the environment. But there's a catch, you need them in sizeable numbers in order for them to effectively work their magic. I think that it's important to mention that water retention in soil is affected directly by the amount of overhead canopy. Ferns and mosses only grow where the moisture in the air is high. As for the trees taking water out of the ground and releasing it into the air, I think you meant to say that it's really just the moisture from precipitation that is trapped by the vegetation, not plants releasing H2O. All this that I'm talking about refers to temperate rain forests. I understand that you're more interested in the conditions specifically relating to the Snohomish/Stillaguamish watersheds. I'm not sure I really answered your question, but hope this is informative at the least.

Rockhopper,

I think what he is referring to is that water is depleted from the soil by tree roots/plants needs. Any tree in question needs some unspecified water to survive throught it's life cyle. You are absolutely correct in the assumption that trees and brush for that matter can act as an isulator/shield to the evaporation of ground water. Once water makes it's way to the ground the plants and trees act as a shield or buffer thereby retaining much of the ground water through shading and cooling -That includes both water in the stream, river, lake, pond & marsh as well as that moisture that fell and beaded or collected at the surface of the soil and plants. Still these plants all need H20 to survive. But the demands are set by the type of climate, geography, individual location, specie, their age and many other factors. And yes, some moisture is lost to the inevitable direct evaporation from the surface of the plants themselves. Snow is a great form of water collection and savings. Most snow falls to the ground and collects there. Only moderate amounts are typically transferred through solar radiation and increased temperatures/sublimation (often above 32 degrees F) relative to the overall water content in the snowpack. -And of course the result is often in the form of run-off besides the typical evaporation rates. Does that help explain things a little??? ;-)

Guys,

Let's don't forget the other plus...more streamside vegetation not only catches more water, it releases it slower.

A lot of our flooding issues (see the Snoqualmie and Skokomish, especially) are greatly exacerbated by the fact that rain hits the ground running and goes straight into the river, bringing whatever soil is left with it, too.

High densisty vegetation lets it out slowly into the river, and cleanly.

Siltation and extreme flows are very bad for redds, obviously, and this is an important factor in protecting them.

Fish on...

Todd.

Trees are always good. The more, the better. If they weren't good for the ecosystem, including the fish the water, the soil, etc, they wouldn't be here. And if it weren't for humans, we'd have alot more of them.

Ah, yes Todd! You hit the nail on the head! Aya karumba -forgot abou that one -shame on me!
Slow-release -very, very important. Very very good grasshoppa!

Fast-run-off - muy malo!

Cohoangler picked up on the real point - salmon and steelhead evolved in and are adapted to old growth forest conditions, that detained, cleansed, and cooled the water and provided huge inputs of woody debris to river systems. Todays forests are so badly modified from their original conditions that I'm surprised that any wild fish survive at all - actually they are going extinct after all, aren't they?