Effects of habitat degradation, microsite, and seed density on the persistence of two native herbs in a subtropical shrubland

Abstract:

PREMISE OF THE STUDY: Species in degraded ecosystems may interact differently withtheir surroundings from those under historic conditions. Understanding factors affecting variation in early life history stages of plants is fundamental to assessing their persistence in intact and degraded habitats, and the value of degraded lands. We evaluated the effect of seed density on the seed dynamics of two herbaceous species (annual, biennial), and considered how seed availability may influence population dynamics in different habitats (degraded, intact Florida scrub) and microsites (bare sand, leaf litter, shrub). M ETHODS: We used data on responses to experimental treatments (seed removal, seedling emergence, establishment) and models to evaluate how effects of these factors may change over time since the last disturbance. KEY RESULTS: Probability of any seed removal, emergence, and establishment per unit increased withseed density, although proportion removal for Chamaecrista fasciculata, proportion emergence for Balduina angustifolia, and proportion establishment for bothspecies decreased withdensity. When animals were given selective access to seeds, invertebrates were primarily responsible for seed removal of bothstudy species. Models withdynamics changing withtime-since-disturbance for bothspecies pbkp_redicted that population growthmay decrease slightly if local available seed density increases. CONCLUSIONS: Detailed demographic comparisons of populations in intact and degraded conditions can be used to understand the way that environmental conditions (habitat, microsite) combine withseed density effects to influence population dynamics of herb species. Degraded habitat may act as a transitional state in a trajectory toward intact conditions for some species, or as refugia for other native species.

Año de publicación:

2015

Keywords:

• Florida
• restoration
• Population dynamics
• anthropogenic disturbance
• Plant populations

Fuente:

scopus