Hi Stephane. 

Interesting question. Like you suggest, lots of different factors will determine water content in plant organs, and this can change throughout the day, seasons etc. and across species.

The paper you link to above is actually describing the RWC at turgor loss point, also known as the wilting point, when plants start to suffer from drought stress. So those RWC quoted are actually quite at the low end. 

As for RWC for a whole tree, I was thinking that Missy Holbrook's lab at Harvard would be a good starting place (http://holbrookgroup.oeb.harvard.edu/home), and sure enough I came across this recent paper of theirs:

http://holbrookgroup.oeb.harvard.edu/publications/water-storage-dynamics-main-stem-subtropical-tree-species-differing-wood 

You should also chase up some older papers of hers too.

Happy reading!

Tim

Thanks Tim, 

This paper does look interesting, I will see if I can find more on their website. Thanks also for explaining the turgor loss point, makes more sense to me now.

Cheers,

Stephane.

The water content varies, depending on tree species and season, but on an average you can calculate with about 50% water in woody tissues.

Dear Stephane,

see a methodology in

http://webdoc.agsci.colostate.edu/hortla/WLB/2007_Cermak_Tree%20water.pdf

Regards, Kees

Thanks Kees, will look at this as well. 

Bengt, I have come across this figure of 50% of the fresh weight on a number of website. I think it sounds quite reasonable, but where does the figure come from? Is there a scientific study behind that number? I thought that surely this would be easy to find, but after few days spent searching, I gave up and decided to ask the experts :).

Stephane:

I feel that may be a significant number of studies showing water content of trees. One of the best times to make this kind of measurement ocurrs when a tree is cut. You have to take enough samples of each organ to obtain the water percentage (by the standard method) which is then converted to kilograms based on the fresh weight of the organ. The summation will be the total liters of water inside the aerial part of the tree.

If the roots are to be considered, a significant amount of them will have to be extracted.

Years ago, we applied this method when measuring the percentage of dry matter in grapevines to estimate the plant nutrient extraction (Table 5 in the annex)

Regards,

Reinaldo

Dear Stephane

You can read these papers.