Large Trees Are Most Influential for Long-Term Persistence of Caribbean Pine (Pinus caribaea var. hondurensis) Populations in Lowland Belize Savannas

Abstract

Caribbean pine (Pinus caribaea var. hondurensis) is the dominant canopy tree in lowland savannas of Central America and naturally experiences frequent fire. Previous research showed differential survival of juvenile pines between open, grass-dominated environments and shrub-dominated savanna environments. To date, however, no studies have modeled the population dynamics of natural stands. We studied Caribbean pine population dynamics in coastal Belize to establish a baseline and determine the relative importance of size-based stages and vital rates to population growth. We collected field data on pines from 2017 to 2021 in open and shrubby environments and grouped individuals into three size-based stage classes. We calculated transition probabilities among stages for two 2-year time intervals (2017–2019, 2019–2021) based on growth and survival and on reproduction, adding them to yield a single matrix for each environment and time interval. These transition matrices were then averaged for each environment, and mean matrices were used to calculate the population growth rates (lambda). We compared these population growth rates with those estimated from simulations using mixed modeling of vital rates, where the time interval was modeled as a random effect. We explored elasticity values for each transition in the mean matrices. Lambda was lower in open than in shrubby savanna environments in both analyses. Population growth rates were most sensitive to the growth and survival of pole and large trees in both savanna environments. Although the elasticity of seedling and juvenile trees was relatively low, these stages are naturally important in both environments, especially after major disturbances such as hurricanes.