DOES TIME SINCE FIRE EXPLAIN PLANT BIOMASS ALLOCATION IN THE FLORIDA, USA, SCRUB ECOSYSTEM?

Although belowground biomass patterns are important in understanding aboveground responses, few studies have quantified how belowground biomass changes in response to fire cycles. In this study, we determined if patterns of time-since-fire (TSF; range 3 yr to 25 yr) affect belowground and aboveground biomass in scrubby flatwoods, a type of Florida, USA, scrub ecosystem. We also examined if plant groups (oaks, palmettos and all other species) show variation in biomass partitioning between belowground to aboveground biomass. We found that TSF had a significant positive impact on shoot biomass of oaks and leaf litter but did not affect total aboveground biomass or the aboveground biomass of other species groups. Total belowground biomass was not significantly explained by TSF, although the belowground biomass of oaks showed a significant quadratic relationship with TSF (r(2) = 0.45, P = 0.023). Mean belowground to aboveground biomass ratios were 3.47 +/- 0.76 overall, 2.18 +/- 0.99 for oaks, 7.25 +/- 1.01 for palmettos, and 4.94 +/- 0.89 for other species. Management of fire-prone ecosystems can use belowground biomass patterns to avoid too-frequent burns that may reduce belowground biomass and affect the ability of ecosystems to respond to subsequent fires. Management actions should also maintain sufficient belowground biomass to buffer against periodic drought.