Background: Resprouting is an effective strategy for persistence of
perennial plants after disturbances such as fire. However, can
disturbances be so frequent that they limit resprouting? We examined
the effects of fire and mowing frequency on eight species of
resprouting shrubs (three oaks (Quercus chapmanii, Q. inopina, Q.
geminata), three ericaceous species (Lyonia fruticosa, L. lucida,
Vaccinium myrsinites), and two palmettos (Sabal etonia, Serenoa
repens)) in Florida scrub using a factorial field experiment. We
burned or mowed plots at four disturbance return intervals (DRI) -
either annually, biennially, every three years, or once in six years
(with all plots being treated in the sixth year to control for
time-since-disturbance). We analyzed plant growth responses (height,
aboveground biomass, number of stems) based on sampling pre-treatment,
and six months, one, two, and four years post-treatment. We also
measured non-structural carbohydrates (NSC) and soil properties to
evaluate these factors as potential drivers of resprouting responses.
Results: Fire temperatures were hot (mean maxima 414-698oC among burn
days), typical of larger fires in Florida scrub. Plant biomass and
heights were affected by DRI (being suppressed by frequent
disturbance, especially initially) and varied among species with
palmettos recovering biomass faster and species within the same genus
generally showing similar responses. Biomass recovery in mown
vs. burned treatments showed comparable effects of DRI and similar
trajectories over time. Numbers of stems were affected by DRI,
disturbance type, and species. Stems increased after disturbances,
especially with less frequent disturbances and mowing, and
subsequently declined over time. NSC concentrations varied among
species and over time and was positively related to biomass. One-year
post-disturbance, soil moisture and organic matter content were higher
in mown plots, while pH was higher in burned plots. Given the slightly
lower elevation of the mown plots, we interpreted these differences as
site effects. Soil properties were not affected by DRI and did not
affect biomass responses.
Conclusions: Although very frequent disturbances reduced shrub growth
responses, the magnitude of plant responses was modest and the effects
temporary. Because resprouting shrubs in Florida scrub appear
resilient to a range of disturbance return intervals, frequent fire or
mowing can be effectively used in restorations.
