Edge‐effects Drive Tropical Forest Fragments Towards an Early‐Successional System

Background

This paper assembles empirical and theoretical evidence to argue that “edge effects” trigger a rapid and inevitable successional process that drives most remaining neotropical forest fragments towards a persistent early-successional system. 

Conclusions & Takeaways

The study found that when forest edges are created , fragments experience a rapid, hyper-proliferation of short-lived pioneer trees, and at the same time, groups of shade tolerant/Old growth species are disfavored and can eventually become rare and may be driven to extinction at the landscale scale.  This process inevitably aggravates the forest biomass collapse caused by increased mortality of large, denser trees near the forest edges, and contributes to the simplification of forest vertical stratification. Furthermore the authors proclaim that the contnued recruitment of pioneers along both recently created and much older “hyper-fragmented” landscapes, and that this supports the hypothesis that pioneer dominated assemblages may be approaching a more stagnant equilibrium condition rather than simply a transient successional stage.  To better understand this, special attention must be given to population level mechanisms driving the recruitment of pioneer and shade-tolerant species since most community/ecosystem-level properties are influenced by the relative importance that these two broad functional groups achieve along successional trajectories.  Namely the way pioneer/shade tolerant species respond to resource availability (light , nutrients and seed dispersal vectora), and also to the selective pressures exerted by herbivores and pathogens.