Experimental Test for Facilitation of Seedling Recruitment by the Dominant Bunchgrass in a Fire-Maintained Savanna

Gwenllian D Iacona,Emilio M Bruna,L Katherine Kirkman,Kurt O Reinhart

doi:10.1371/journal.pone.0039108

Gwenllian D Iacona, Emilio M Bruna + Show 2 more

Open Access

https://doi.org/10.1371/journal.pone.0039108

Copy DOI

Journal: PLoS ONE	Publication Date: Jul 6, 2012
Citations: 43	License type: CC BY 4.0

Affiliation: University of Florida, The Jones Center at Ichauway

Abstract

Facilitative interactions between neighboring plants can influence community composition, especially in locations where environmental stress is a factor limiting competitive effects. The longleaf pine savanna of the southeastern United States is a threatened and diverse system where seedling recruitment success and understory species richness levels are regulated by the availability of moist microsites. We hypothesized that the dominant bunch grass species (Aristida stricta Michx.) would facilitate moist seedling microsites through shading, but that the effect would depend on stress gradients. Here, we examined the environmental properties modified by the presence of wiregrass and tested the importance of increased shade as a potential facilitative mechanism promoting seedling recruitment across spatial and temporal stress gradients. We showed that environmental gradients, season, and experimental water manipulation influence seedling success. Environmental properties were modified by wiregrass proximity in a manner that could facilitate seedling success, but we showed that shade alone does not provide a facilitative benefit to seedlings in this system.

Highlights

Facilitative interactions occur when a plant enhances the success of another [1]. Because these relationships can influence patterns of community composition, identifying the extent of facilitation and its underlying mechanisms is important for understanding the drivers of plant diversity [2]
The nature of the interaction may vary across a continuum determined by environmental stress gradients, with competitive effects dominating in optimal conditions and facilitation prevailing in harsher ones [2,3,6]
We have shown that water availability regulates diversity of seedling species in this system, which suggests that heterogeneity in the availability of moist microsites influences community composition [16]

Summary

Introduction

Facilitative interactions occur when a plant enhances the success of another [1]. Because these relationships can influence patterns of community composition, identifying the extent of facilitation and its underlying mechanisms is important for understanding the drivers of plant diversity [2]. The nature of the interaction may vary across a continuum determined by environmental stress gradients, with competitive effects dominating in optimal conditions and facilitation prevailing in harsher ones [2,3,6]. These stress gradients may be temporal (e.g. inter-seasonal differences [7]), or spatial (e.g., gradients in soil moisture [4], or salinity [8]). Nurse plants can facilitate recruitment by modulating temperature highs and lows beneath their canopy [13]

Methods

Results

Conclusion