A model for predicting seedling performance of an exotic shrub, Amur honeysuckle (Lonicera maackii), and its implications for invasion

Amur honeysuckle (Lonicera maackii) is a non-indigenous shrub which has escaped cultivation in most of the eastern US. Considerable research has been conducted regarding its negative effects on indigenous plants; however, no study has generated a predictive model regarding seedling establishment by investigating its growth and biomass allocation in a controlled environment. We conducted a fully-crossed factorial design (n = 16 per treatment combination) using light (10%, 50%, and full sun), water availability (soil watered to 50% and 100% field capacity biweekly), and soil type (glaciated and unglaciated from southwest and southeast Ohio, respectively). Multiple regression tree (MRT) analysis was successful in predicting seedling growth (variance explained). Light intensity was the most important factor in explaining overall seedling performance. Water availability was more important for predicting seedling growth for the first year of seedling establishment versus the second year, and greater total biomass was found in the high light versus medium light environment regardless of water availability, which implies extreme tolerance to drought even in full sun. In all light and water treatment combinations, growth in the glaciated soil was greater than in the unglaciated soil, which is supported by our findings of greater nutrient availability in glaciated soil. Overall, this species’ performance was facilitated by high water availability in the first year of seedling establishment and high light conditions at the later juvenile stage (second year). These data suggest that knowledge of abiotic conditions is important for predicting performance during establishment and will also likely prove to be important in prioritizing potential removal and restoration sites.