Agriculture Reference
In-Depth Information
fires. The most dependable and ubiquitous plant trait that provides resilience in
fire-prone landscapes is resprouting ability. With life histories such as herbaceous
perennials, which have an annual cycle of top dieback followed by growing season
regrowth, some level of pre-adaptation was involved in adapting to fires. How-
ever, in woody plants there are many lineages where it seems likely that resprout-
ing was selected for and has been continually maintained by fire. The Late
Cretaceous and early Tertiary development of sclerophyllous MTV initiated a
new era in plant-fire relations. Today this vegetation dominates MTCs but has its
origins in climates and/or soils that shared primarily two characteristics with
contemporary MTCs: (1) growing seasons conducive to production of sufficient
biomass to form contiguous fuels and (2) seasonality that varied in timing and
regularity but was sufficient to make the vegetation fire-prone and sufficient to
limit growth so that fires were stand-consuming crown fires. Under extreme
conditions there was selection for fire-dependent reproduction because the prefire
closed canopy limited recruitment opportunities and the postfire conditions
opened up gaps sufficient for seedling populations to exploit resources made
available only by fire. The late Tertiary intensification of summer drought greatly
expanded the amount of landscape available for regular high-intensity crown fires
and associated with this was an expansion of MTV in MTC regions. However,
even on the most fire-prone landscapes present today, fire regimes are not always
conducive to generating gaps sufficiently predictable for seedling recruitment.
Thus, MTC communities often comprise mixtures of obligate resprouters and
obligate seeders, each exploiting different portions of available niche space.
