Community control on growth and survival of an exotic shrub

Abstract

A top priority in the field of invasion ecology is to investigate the mechanisms that lead to the successful establishment and spread of harmful exotic species. Studying plant invasions in the context of the invaded community can help us to understand those mechanisms. In this study, we follow a community approach where we describe establishment and growth patterns of an exotic shrub, Elaeagnus umbellata, with respect to the local woody plant community. Primarily focusing on a forest ecosystem, we expect light availability to be a driving factor in the recruitment of E. umbellata individuals; however, this is not supported for seedling recruitment as light becomes detrimental to survival in conditions exceeding 30 % full sun. Instead, growth of first year seedlings is primarily affected by soil moisture. Forest census data of adult individuals show that growth of E. umbellata is affected by light and small-scale neighborhood density (i.e., limited in the understory by space or resources), suggesting a shift in resource requirement. Overall, our study indicates that although E. umbellata individuals are likely to recruit and persist in the understory, successful growth to adulthood is controlled by competitive interactions.