Where can I find the salinity of the soil in the Amazon Rainforest?
Since this is not my area of expertise, I searched Google under the key words "'Amazon rainforest' soil salinity" to get these possible sources:
http://news.mongabay.com/2005/1222-duke.html
(Broken Link Removed)
http://en.wikipedia.org/wiki/Amazon_River
http://www.bio-medicine.org/biology-news/Research-3A-Snails-were-overlooked-contributors-to-marsh-destruction-2047-1/
http://igitur-archive.library.uu.nl/dissertations/2003-1020-094848/c5.pdf
In the future, you can find the information you desire more quickly, if you use appropriate key words to do your own search.
I hope this helps. Thanks for asking.