Biochemical weathering of calcium-bearing minerals by rhizosphere micro-organisms,and its influence on calcium accumulation in trees

Summary The rhizosphere microflora of redcedar was found to have a higher percentage of calcium silicate-solubilizing rhizosphere bacteria than the rhizosphere microflora of white pine of similar age growing in the same locality under identical conditions. Though the species composition of the silicatesolubilizing microbial population varied considerably from winter to spring, the redcedar roots had more silicate-solubilizers than the white pine roots inboth seasons. Since redcedar is known to have a higher calcium content than white pine, these results indicate that calcium accumulation by redcedar and white pine is strongly influenced by the rate at which calcium is released from soil minerals by the weathering action of the trees' rhizosphere micro-organisms. A symbiotic relationship between the trees and the microflora is suggested.