Klinczar, Angela , Freeman, Charlotte , Angeli, Nicole , Gorchov, David .
The Effect of Treefall Gaps on the Spatial Distribution and Dispersal of Four Invasive Plants in a Mature Secondary Forest in Maryland.
Plant invasion is contingent on several factors; the most prominent being invasibility and propagule rain. Propagule rain measures the degree to which an established invasive species contributes seeds to the environment. Invasibility, the intrinsic susceptibility of an area to invasion, is typically high in disturbed areas. The objective of this study is to determine the spatial distribution of invasive plants in a mature forest, to explore the role of disturbance (specifically treefall gaps) and propagule rain in plant invasion, and to investigate the role of diffusion and long-distance dispersal. Nine hectares of secondary upland forest, divided into 2x2 m subplots, were surveyed at the Smithsonian Environmental Research Center in Maryland, USA. This stand is part of the global network of permanent forest plots coordinated by the Center for Tropical Forest Sciences (CTFS). For each subplot, invasive plants were identified, and, for the four most abundant invaders, Rubus phoenicolasius, Berberis thunbergii, Rosa multiflora, and Lonicera japonica, numbers were counted per life history stage. The height of the canopy was assessed for each subplot, and later scored to reflect gap (<10 m) and non-gap (>10 m). Focal statistics utilizing the median were conducted with Geographic Information Systems (GIS), implementing a 3x3 m rectangle neighborhood to reclassify these points and make more contiguous gap polygons. We will use GIS and spatial statistics as tools to assess predictors of the spatial pattern of these invasive plants, particularly the importance of treefall gaps and a nearby propagule source, a recently logged stand. Preliminary visual analysis with GIS indicates that L. japonica has no gap restriction and is found throughout the forest, in 39% of subplots. The other three species are less frequent, and R. phoenicolasius colonization appears to be influenced the most by gaps. In order to investigate the importance of gap dynamics to invasion, we will test whether the distributions of different life history stages of each species are associated with gaps. Within this we will test whether reproduction is restricted to gaps, or gaps above a threshold size. We will assess if dispersal distance is limited from both the logged stand and established reproductive plants in the plot. The implications of this study are to understand the mechanisms of invasion and importance of site conditions, which must be known in order to implement control and management.
1 - Miami University, Botany, 700 E. High St, Oxford, OH, 45056, USA
2 - Texas A&M University, Wildlife and Fisheries Sciences, College Station, TX, 77840, USA
3 - Miami University, Department Of Botany, 316 Pearson Hall, Oxford, OH, 45056, USA
Presentation Type: Oral Paper:Papers for Sections
Candidate for Awards:Ecological Section Best Graduate Student Paper