Microhabitat analysis of the invasive exotic liana Lonicera japonica Thunb

We documented microhabitat occurrence and growth of Lonicera japonica to identify factors related to its invasion into a southern Illinois shale barren. The barren was surveyed for L. japonica in June 2003, and the microhabitats of established L. japonica plants were compared to random points that sampled the range of available microhabitats in the barren. Vine and leaf characters were used as measurements of plant growth. Lonicera japonica occurred preferentially in areas of high litter cover and species richness, comparatively small trees, low PAR, low soil moisture and temperature, steep slopes, and shallow soils. Plant growth varied among these microhabitats. Among plots where L. japonica occurred, growth was related to soil and light conditions, and aspects of surrounding cover. Overhead canopy cover was a common variable associated with nearly all measured growth traits. Plasticity of traits to improve invader success can only affect the likelihood of invasion once constraints to establishment and persistence have been surmounted. Therefore, understanding where L. japonica invasion occurs, and microhabitat interactions with plant growth are important for estimating invasion success.