Long-term demographic data can provide information on variation in vital rates among years, sites and species that can be used to contrast life history syndromes. Here, we analyze vital rates from 14 species (nine of which are federally-listed) over as many as 22 years in Florida xeric uplands (Florida scrub and sandhill), pyrogenic ecosystems dominated by shrubs and herbs. Over 50,000 individual plants, marked and/or mapped in permanent plots, provide estimates of annual survival (excluding seedlings) and relative growth rates (RGR; based on height, rosette diameter or number of stems, depending on the species). We are particularly interested in comparing vital rates in years with (or without) the two dominant disturbances in Florida uplands: fire and hurricanes. In addition, we contrast these vital rates between species that typically resprout following fire and those that are killed by fire.
Results/Conclusions
Annual survival of non-seedlings varied from 48-99% among species (0-100% for individual years). Sprouters had significantly higher survival (91%) than non-sprouters (65%). Fire almost always kills non-sprouting individuals, but four sprouting species with sufficient data had similar survival rates whether burned or not. Survival varied significantly among species but did not vary among years, including between years with major hurricanes (76%) and without major hurricanes (74%). RGR also varied widely among species, with Dicerandra thinicola having the highest growth rates. Ceratiola ericoides cohorts were unique in combining high survival with high RGR. Reprouter RGR bracketed zero (no net growth) and were significantly lower than RGR for seeders, which was significantly greater than zero. Resprouting shrubs showed negative growth from before to after fire, but resprouting herbs tended to be larger post-fire than before. Overall, RGR varied by species and marginally among years, with a significant species by year interaction. Life history syndromes in these species followed the resprout/not resprout dichotomy, suggesting that the ecological disturbance usually causing resprouting (fire) has been an important selective force.
