Premium
Biologically induced mineralization in the tree Milicia excelsa (Moraceae): its causes and consequences to the environment
Author(s) -
Braissant Olivier,
Cailleau Guillaume,
Aragno Michel,
Verrecchia Eric P.
Publication year - 2004
Publication title -
geobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.859
H-Index - 72
eISSN - 1472-4669
pISSN - 1472-4677
DOI - 10.1111/j.1472-4677.2004.00019.x
Subject(s) - mineralization (soil science) , oxalate , chemistry , sodium oxalate , biomineralization , calcium carbonate , botany , environmental chemistry , calcium oxalate , plant litter , soil water , ecology , biology , inorganic chemistry , organic chemistry , paleontology , nutrient
ABSTRACT Iroko trees ( Milicia excelsa ) in Ivory Coast and Cameroon are unusual because of their highly biomineralized tissues, which can virtually transform the trunk into stone. Oxalic acid (C 2 O 4 H 2 ) and metal‐oxalate play important roles in their ecosystems. In this study, the various forms of oxalate and carbonate mineralization reactions are investigated by using scanning electron microscopy and X‐ray diffraction. Calcium oxalate monohydrate is associated with stem, bark and root tissues, whereas calcium oxalate dihydrate is found with wood rot fungi in soils, as well as in decaying wood. Laboratory cultures show that many soil bacteria are able to oxidize calcium oxalate rapidly, resulting in an increase in solution pH. In terms of M . excelsa , these transformations lead to the precipitation of calcium carbonate, not only within the wood tissue, but also within the litter and soil. We calculate that c . 500 kg of inorganic carbon is accumulated inside an 80‐year‐old tree, and c . 1000 kg is associated with its surrounding soil. Crucially, the fixation of atmospheric CO 2 during tree photosynthesis, and its ultimate transformation into calcite, potentially represents a long‐term carbon sink, because inorganic carbon has a longer residence time than organic carbon. Considering that calcium oxalate biosynthesis is widespread in the plant and fungal kingdoms, the biomineralization displayed by M. excelsa may be an extremely common phenomena.