# transpiration rates



## begleytree (Jan 10, 2007)

Does anyone here have any good figures for tree transpiration rates? We all know that trees draw moisture and help dry out wet spots, but how much is drawn, how much is retained, and how much is lost to the atmosphere?
If no one has any real numbers, I would also welcome educated guesses.
It's just something I'm thinking about, well, a part of something anyway.
-Ralph


----------



## NYCHA FORESTER (Jan 10, 2007)

Too many variables:
Species, Condition, canopy volume, temperature, xylem volume, wind speed, soil type, soil moisture, root volume, length of daylight, strength of daylight... to name just a few


----------



## Grace Tree (Jan 10, 2007)

That's a question I get asked all the time, ususally in the form of; "How wet is it going to be with the willow or cottonwood.... gone?" I'd also welcome some wisdom; even if it's rule of thumb folklore wisdom. It's better than saying I dunno.
Phil


----------



## Grace Tree (Jan 10, 2007)

Ralph. That sounds excessive to me. Even more so if you think in terms of multiple trees. 100 trees would use 200,000 gallons. At that rate walking through the woods in Ohio would be like walking in the rain forest. Am I missing something?
Phil


----------



## ATH (Jan 10, 2007)

Yeah, 2000 gal per tree per day sounds very excessive. Maybe that is per month (still sounds high) or per year? Or per acre of 6" trees per day???

From USGS"During a growing season, a leaf will transpire many times more water than its own weight. An acre of corn gives off about 3,000-4,000 gallons (11,400-15,100 liters) of water each day, and a large oak tree can transpire 40,000 gallons (151,000 liters) per year."

So, lets say we have 200 growing days (to make the math easy...), that translates into 200 gallons per day. I was going to post that I had always heard a big oak will do a "couple of hundred gallons per day", but wanted to find more info - for myself too.

This site says 25-50 gallons for 5 year old hybrid poplar (probably close to 6")...Comes out close to 6000 gallons per acre per day.

If you really want to know...Here is some good reading Please read and report back what we really need to know


----------



## ATH (Jan 10, 2007)

I'm not a farmer, but I work with a lot of them at different times.

30" rows are the norm, I think...
spacing between plants can vary, but I think 7" is "normal".

30"x7" = 29,870 plants per acre.


----------



## NickfromWI (Jan 10, 2007)

2000 gallons of water per day sounds very high. That would be over 16,000 pounds of water per day. A six inch tree would not even weigh close to 16,000.

According to this website, http://ga.water.usgs.gov/edu/watercycleevapotranspiration.html

A large oak can transpire about 110 gallons per day. So for a 6" tree, maybe the number is closer to 20 gallons per day?

love
nick


----------



## NickfromWI (Jan 10, 2007)

Regarding the corn, unfortunately the range is quite high. It's like 15,000 to 25,000 stalks per acre depending on if you're planting small ear or large ear corn. For your calculations maybe you can just use 20,000 stalks/acre?

love
nick


----------



## MarsCrash (Jan 11, 2007)

A 6" tree wouldn't weigh 16,000 lbs even if it transpired that much.

You wouldn't weigh a straw full of liquid by including everything that went through it, would you?


----------



## Ekka (Jan 11, 2007)

75% of moisture absorbed by the tree is released back into the atmosphere.


----------



## ATH (Jan 12, 2007)

Ekka,
That sounds a little low to me...not that I have reasearched it -- just initial reaction is that 75% doesn't seem like enough. Have you read that some where or is it a "general rule of thumb"? O am sure it varies by species, but probably not more than a few percentage points.

I guess there is a lot of weight in the leaves that stays there (until they fall, after which they release their water, but I wasn't thinking of that water in the 75%). Just got me curious.

Curious to do the math...
40,000 gallons per year = 320,000 pounds. 25% of that is 80000 pounds...per year???

I know your point was you can't weigh the tree to figure out how much water it transpired. I think this (overly-simplified) equation only proves your point further.


----------



## Ekka (Jan 12, 2007)

On this here we have 90%.

http://au.answers.yahoo.com/question/index.php?qid=20061228064002AAsHkYk

And I stand to be corrected and my answer should read ...

75% of the precipitation that lands on forests is returned to atmosphere in a combination of evaporation and transpiration.

This is a great link and well kept secret of mine.

http://www.rainforestinfo.org.au/good_wood/trees_gs.htm#anchor440268

So, a better way to write it is how it appears on my website ... "Trees also recycle the water, approximately 90% of the water absorbed by a trees' roots is put back into the atmosphere as part of photosynthesis and transpiration. Also, 75% of the rain that falls on a forest is returned to the atmosphere by a combination of transpiration and evaporation."

http://www.palmtreeservices.com.au/weareallabouttrees/ is the parking address of my new website till I move it to it's own hosted domain.


----------



## Tom Crosthwaite (Feb 27, 2017)

I wonder if there is a scientific way to classify different levels for different types of trees other than averaging it out for all trees, I know it would be a huge task that no company would see the point or profit in sponsoring, but it would be interesting to know. I can just imagine that there is a huge diversity between species, for example tropical compared to species whose natural habitat is drought prone. NC State university states that a large tree can lift up to 100 gallons of water out of the ground and discharge it into the air in a day https://projects.ncsu.edu/project/treesofstrength/treefact.htm I do question how accurate this rule of thumb is when applied to all species. From us at http://trickytreesolutions.com/


----------



## ATH (Mar 2, 2017)

Tom Crosthwaite said:


> I wonder if there is a scientific way to classify different levels for different types of trees other than averaging it out for all trees, I know it would be a huge task that no company would see the point or profit in sponsoring, but it would be interesting to know.....


I disagree (kinda). There is huge benefit in knowing transpiration rates. Storm water mitigation is a very significant benefit of urban trees. Where I still agree: a company wouldn't necessarily profit enough to cover the cost of the research. This would need to be funded by USFS or the like.


----------



## BC WetCoast (Mar 2, 2017)

I'm pretty sure much of that work has been done in the universities by grad students. I would suspect done more for forestry trees in native environments at this point. The research of tree physiology in the urban environment isn't quite as far along and most of the research funding early on was for growing trees for timber.

It's just a matter of doing the literature reviews and abstract reading of thousands of grad theses.


----------



## ATH (Mar 3, 2017)

Good point. When I was at Virginia Tech 20 years ago, they had studies with artificially isolated watersheds to study the impacts of Loblolly pine. It sucked up a lot of water and made the water that came out of the stands much cleaner...


----------



## hanniedog (Mar 3, 2017)

Can't believe there is still a begleytree thread still around


----------

