Distribution and success of native and invasive Phragmites australis in northern Michigan

Abstract

Phragmites australis, or common reed, is represented by several subspecies (haplotypes) in North America. The native haplotypes are important components of wetland ecosystems, while a non-native haplotype introduced in the nineteenth century has become an aggressive invader. The goals of this study were to characterize the native and invasive haplotype distribution of Phragmites in northern Michigan, to determine which environmental characteristic are correlated with native, invasive, and overall Phragmites success, and to analyze the trends so that local potential predictors of Phragmites variable distribution and success might be identified. Fourteen wetlands were surveyed for native and invasive Phragmites stands. Ten native and four invasive stands were sampled. Environmental variables (including temperature, pH, proximity to human development, surface moisture, water conductivity and DO) and variables related to Phragmites success (stand area and density, height and diameter of the tallest stem, and leaf litter depth) were measured. In addition, each Phragmites site was paired to a similar site with no Phragmites. The data was compared for native, invasive, and control sites using paired T-tests and regressions. Temperature, human development, and, to some extent, water pH were found to be significantly linked to Phragmites haplotype variable distribution and success. Despite the limitation of small sample size, these early trends could be of particular relevance for land managers working to protect wetlands and slow invasive success. Among the environmental characteristic variables, temperature measurements resulted in the most comparisons with significance. Increased temperature seems to be linked to increased invasive success and decreased native success, with potential implications regarding the affects of climate change on wetlands in northern Michigan.