Made in the Shade
Are closed-canopy forests truly less susceptible to invasion by exotic plant species as compared with disturbed forests, or has the “biotic resistance” of these intact communities been overstated? In “Why forests appear resistant to exotic plant invasions: intentional introductions, stand dynamics, and the role of shade tolerance”, a paper published in the April issue of Frontiers in Ecology and the Environment, Patrick Martin and his coauthors Charles Canham and Peter Marks suggest that the apparent resistance of established forests to exotic invasion may indeed be largely illusory. Noting that invasion ecology has largely concentrated on early-successional, disturbance-adapted species, the authors point out that research on late-successional, shade-tolerant invasive plants – many deliberately introduced by humans – has largely been overlooked. In this month’s edition of Beyond the Frontier, Dr. Martin discusses the theory behind forest invasions by exotic plant species, the roles that shade tolerance and horticultural practices play in the process of understory invasion, and the challenges associated with invasive management within forest ecosystems.