Abstract
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 Flor ida, 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 rela tionship 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.
Highlights
Fire regimes play an important role in biomass allocation patterns
While total aboveground biomass did not show a significant increase with TSF (r2 = 0.067, P = 0.182), aboveground biomass of oaks significantly increased with TSF (r2 = 0.29, P < 0.05; Figure 1)
In the Florida scrub ecosystem, patterns in aboveground biomass in relation to time-sincefire varied among plant functional categories, while the total aboveground biomass pooled across all plants was not significantly affected by TSF
Summary
In fireprone ecosystems, total plant biomass, growth rates, and distribution of biomass between roots and shoots is influenced by fire intensity and frequency (Pare and Bergeron 1995, de Vinas and Ayanz 2000, Dijkstra et al 2002, Day et al 2006, Mack et al 2008). Ecosystem-level patterns of plant biomass in relation to TSF, especially for roots and other belowground organs, are poorly understood (Williams et al 2008). Understanding the patterns in biomass distribution between aboveground and belowground biomass sheds light on ecosystem processes such as carbon sequestration and water table dynamics (Feddes et al 2001, Day et al 2006, Collins and Braas 2007, Rodriguez-Iturbe et al 2007, Sierra et al 2007)
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