Title: Emergence and performance of two invasive Swallow-worts (Vincetoxicum spp.) in contrasting soil types and soil pH Authors
|Magidow, Lillian -|
|Ditommaso, Antonio -|
|Ketterings, Quirine -|
|Mohler, Charles -|
Submitted to: Journal of Invasive Plant Science and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 4, 2013
Publication Date: June 6, 2013
Citation: Magidow, L.C., Ditommaso, A., Ketterings, Q.M., Mohler, C.L., Milbrath, L.R. 2013. Emergence and performance of two invasive Swallow-worts (Vincetoxicum spp.) in contrasting soil types and soil pH. Journal of Invasive Plant Science and Management. 6:281-291. Interpretive Summary: Two introduced plants, pale and black swallow-wort, have become an invasive weed problem in northeastern North America. Currently, there is little overlap at field sites of the two species. Using both a field and laboratory study, we found that seedling emergence was generally not affected by soil pH, although soil type could influence germination rates. The effect of soil pH and soil type on subsequent growth, survival and reproduction of first-year plants was variable. Based on our findings in this study, it appears that these two species can colonize and grow well in soils with a relatively wide range of pH values. From a management perspective, our results suggest that the current range and local overlap of these two species will continue to increase and that early detection-rapid response programs should be established in susceptible regions not yet colonized by these two invasive vines.
Technical Abstract: The alien invasive vines black and pale swallow-wort are currently spreading across eastern North America, invading parklands, old fields, restored forest sites, and other natural areas. These plants spread by wind-borne seed and can form dense stands where they become established. Although their current geographic ranges overlap, there is little known overlap locally. Preliminary observations and anecdotal information have associated black swallow-wort with low-pH inceptisols and pale swallow-wort with high-pH alfisols. We conducted a common garden field experiment during two years and a growth chamber germination experiment to assess whether seedling emergence and performance of these two swallow-worts are affected by soil type and/or soil pH. In the common garden experiment, plants of both species grown on the Onondaga County soil type (an alfisol) produced a smaller root mass than on the Orange County soil (an inceptisol). Also, in one of two years more seedlings emerged and plants produced more follicles on the Onondaga County soil. Soil pH did not affect seedling emergence, although plants grown on low pH soils had a smaller root dry mass compared with plants grown on higher pH soils. Soil pH effects on stem length, stem dry mass, and follicle production were inconsistent among years. Species differences were also evident, with more pale swallow-wort seedlings emerging than black swallow-wort seedlings, whereas black swallow-wort plants mostly had greater biomass and fecundity than pale swallow-wort plants. In the growth chamber experiment, final percentage seed germination was greater on the Onondaga County soil than on the Orange County soil. The germination speed index as well as the probability to reach 50% germination for black swallow-wort was higher on the Onondaga County soil than the Orange County soil, but only at lower pH levels. The germination speed index of pale swallow-wort on the Orange County soil was higher than black swallow-wort at low, but not high, pH levels. In contrast, black swallow-wort had a higher probability of reaching 50% germination than pale swallow-wort on the Orange County soil at higher pH levels. Contrary to our expectations, interactions between the two swallow-wort species with their associated soil type or with their presumably preferred soil pH were weak, contradictory or non-existent in either experiment. This suggests that these two species can colonize and grow well in a relatively wide range of soil pH conditions. From a management perspective, our results suggest that the current range and local overlap of these two species will continue to increase and that early detection rapid response (EDRR) programs should be established in susceptible regions not yet colonized by these two invasive vines.