Mark -- In reply to your query about effects of charcoal, here are at least a few thoughts (others please correct anything that seems wrong). My understanding of Mn toxicity in tropical soils is that it's most common where there are large accumulations of SOM. The high rates of decomposition create a reducing environment that lowers the oxidation state of the Mn, making it more soluble. Seems to me Pedro Sanchez talked about this in his book and may have cited some refs (of course they'll be 17 years out of date -- Pedro, when do we get a revision???). Whether that's a factor in your case is unclear. I would expect the charcoal to be pretty inert unless perhaps it's very finely divided (you mention dust?). You might then want to measure rates of respiration from your soils. Did other organic forms accumulate along with the charcoal, perhaps having been distilled out during the heat and trapped in the soil? (I presume the wood was buried under soil once the fire was started?) Incidentally, does anyone know of a good technique for quantifying the amount of charcoal in soil? I'm interested in all of this, in part because charcoal is a ubiquitous component of forest soils in general, and in part because I'm helping with a study of the origins of anthropic soils at Maya occupied sites in Belize. -- Phil Sollins ----------------------------------------------------------- | Phillip Sollins <sollinsp@ccmail.orst.edu> | | Associate Professor <sollins@fsl.orst.edu> | | Forest Science Dept. | | Oregon State Univ. Tel: 503-737-6582 | | Corvallis, OR 97331-5705 Fax: 503-737-1393 | -----------------------------------------------------------
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