Effects of Prescribed Fire at Two Frequencies on N Mineralization and Nitrification at Two Spatial Scales in Mixed-Oak Forests
2005
Boerner, R.E.J. | Brinkman, J.A.
This study examined how fire frequency influences soil C and N dynamics in relation to spatial scale in two mixed-oak forest complexes in southern Ohio, U.S.A. We measured net N mineralization, net nitrification, total inorganic N (TIN) in the soil solution, and soil organic C in plots of two sizes (50 m2 macroplots and 1 m2 microplot nested within the macroplots) in sites burned once (periodic fire treatment), in sites burned three times (annual fire treatment) and in unburned control sites. N mineralization rate increased with increasing fire frequency and net nitrification was greater in soils given annual fire sites than in soils given periodic fire or no fire (control); in contrast, neither TIN nor soil organic C content were affected significantly by fire. Geostatistical analysis designed to detect spatial autocorrelation (patch structure) at sizes of 0.2 - 0.8 m (microplots) and 1.0 - 7.8 m (macroplots) revealed significant patch structure in only approximately 1/3 of the plots, and all of those had been recently burned. Comparison with studies done in these sites and others indicates that most spatial structure in soil properties occurs at ranges larger and smaller than those that could be resolved with this sampling design. Prior studies of the effects of fire on forests have suggested that fire enhances fine scale heterogeneity, though robust geostatistical analysis of patch structure has not often been part of such studies. The results presented here lend quantitative support to the view that reintroduction of low intensity fire can restore native ecosystem spatial heterogeneity, and thereby help maintain overall plant species diversity and opportunities for the regeneration of diverse tree species.
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