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Harvard Forest Symposium Abstract 2007
- Title: Effects of historical agriculture and contemporary logging activity on the population structure of Japanese barberry
- Primary Author: Brian DeGasperis (Harvard Forest)
- Additional Authors: Kristina Stinson (University of Massachusetts - Amherst )
- Abstract:
Attempts to determine characteristics that render habitats invasible to non-native species have met with limited success. This may be because most studies focus on modern habitat conditions and do not consider invasibility in the context of a historically dynamic landscape in which both the abundance of a species and the invasibility of a site may change. In the summer of 2005, we surveyed 159 currently forested sites for the occurrence and abundance of Berberis thunbergii (Japanese barberry), an invasive, non-native shrub in forests of the northeastern U.S., relative to modern environmental and edaphic conditions, contemporary logging activity, and historical land use. Berberis thunbergii occurred more frequently and was more abundant in post-agricultural forests than in continuously wooded sites. This relationship was stronger for agricultural sites that were abandoned and reforested after B. thunbergii was introduced to the region than for sites that reforested prior to B. thunbergii introduction. In contrast, recent forest harvesting did not influence the occurrence or abundance of B. thunbergii at the landscape scale. While land-use history covaries with soil fertility and distance to putative seed sources, the strong relationship between modern abundance patterns and historical agriculture suggests that B. thunbergii colonized abandoned agricultural lands in the early 20th century and then persisted and spread locally during subsequent reforestation.
In order to further investigate the mechanisms underlying B. thunbergii invasion and elucidate the patterns observed across the broader landscape, a study was initiated in autumn of 2005 to examine the population structure and dynamics of B. thunbergii on sites with different agricultural and logging histories. Within each of fifteen invaded sites, we measured environmental and edaphic characteristics and quantified B. thunbergii stem density, percent cover, and fruit production in three 2 x 2 m plots. In spring of 2006, all B. thunbergii stems in sampled plots were cut at ground level and aged by counting annual growth rings. These data will be used to create population age structure models for comparison between sites. If certain assumptions are accepted, observing the age-density distribution of a standing population can be a time-specific method used to develop stem survivorship curves. We believe this dendrological approach can provide valuable supplementary information for studies on the population ecology of invasive woody shrubs with clearly demarcated annual rings.
- Research Category: Historical and Retrospective Studies
Invasive Plants, Pests & Pathogens
Physiological Ecology, Population Dynamics, and Species Interactions
