N fixation, soil acidity & vegetation type
I'm looking for comparative data on nitrogen-fixation rates per hectare
(by all fixers, free-living and symbiotic) among different natural
vegetation types. Specifically, I want to see data relating ecosystem
N-fixation rates to variation in soil acidity and soil organic matter.
A comparison of N-fixation rates among upland heaths, upland conifer
forests, oak forests, and upland non-oak hardwood forests would be
If textbooks deal with the relationship between N fixation and soil
acidity at all, it's usually by mentioning the pH tolerances of N
fixers. For example, Beijerinckia are said to fix from pH 3 to 9,
Azotobacter, above pH 6, Rhizobium with legumes, above pH 5, etc. But
I'm looking for a comparizon of integrated fixation rates among
vegetation types that differ in soil acidity and type of soil organic matter.
References will be much appreciated.
Department of Geology, University of Pennsylvania