Effects of spring and fall burns on C3 and C4 productivity

Abstract

A lack of information about the differing effects of fall and spring burns on aboveground net primary production of C3 forbs and C4 grasses prevents discovery of optimal restoration management techniques for the tallgrass prairie. In order to make progress toward this goal, our study examines how the above-ground biomass and abundance of the late-flowering C3 species Lespedeza capitata and Solidago canadensis variety scabra, as well as the late-flowering C4 grasses Andropogon gerardii and Sorghastrum nutans are affected by spring burn, fall burn, and no burn treatments. We measured total nitrogen and moisture content of the soil, as well as light availability in order to examine possible correlations of these factors with different levels of productivity of the species examined. Although most previous studies have assumed similar productivity patterns resulting from spring and fall burn treatments, we found trends of greater production in C3 L. capitata and C4 S. nutans in spring burn regimes as compared to fall burn regimes. We also found significantly higher productivity and abundance of A. gerardii in both burned treatments than in unburned treatments. There were no correlations between increased production in these species with soil moisture, total nitrogen or light intensity levels. However, rhizomatous stimulation in early season growth resulting from increased solar radiation on soil could be a possible cause for this response to fire.