Succession of Ephemeral Secondary Forests and Their Limited Role for the Conservation of Floristic Diversity in a Human-Modified Tropical Landscape

Abstract

Both local- and landscape-scale processes drive succession of secondary forests in human-modified tropical landscapes. Nonetheless, until recently successional changes in composition and diversity have been predominantly studied at the patch level. Here, we used a unique dataset with 45 randomly selected sites across a mixed-use tropical landscape in central Panama to study forest succession simultaneously on local and landscape scales and across both life stages (seedling, sapling, juvenile and adult trees) and life forms (shrubs, trees, lianas, and palms). To understand the potential of these secondary forests to conserve tree species diversity, we also evaluated the diversity of species that can persist as viable metapopulations in a dynamic patchwork of short-lived successional forests, using different assumptions about the average relative size at reproductive maturity. We found a deterministic shift in the diversity and composition of the local plant communities as well as the metacommunity, driven by variation in the rate at which species recruited into and disappeared from the secondary forests across the landscape. Our results indicate that dispersal limitation and the successional niche operate simultaneously and shape successional dynamics of the metacommunity of these early secondary forests. A high diversity of plant species across the metacommunity of early secondary forests shows a potential for restoration of diverse forests through natural succession, when trees and fragments of older forests are maintained in the agricultural matrix and land is abandoned or set aside for a long period of time. On the other hand, during the first 32 years the number of species with mature-sized individuals was a relatively small and strongly biased sub-sample of the total species pool. This implies that ephemeral secondary forests have a limited role in the long-term conservation of tree species diversity in human-modified tropical landscapes.

Changing gears during succession: shifting functional strategies in young tropical secondary forests

“…Beyond mechanisms affecting interspecific variation in performance or shade tolerance (Pickett et al 1987;van Breugel et al 2013), our data also suggest that changes in functional composition during secondary succession are determined by stochastic processes, e.g., dispersal limitation and previous land-use history. Following the framework of Pickett et al (1987), competition for growthlimiting resources is conditional upon site and species availability.…”

“…This is the most dynamic phase of succession, during which quick shifts in species composition occur in parallel with rapid changes in forest structure and micro-climate (Lebrija-Trejos et al 2008;van Breugel et al 2013). 'Hard' traits (e.g., photosynthesis) have direct, mechanistic links with multiple aspects of plant performance, yet 'soft' functional traits (e.g., specific leaf area and leaf dry matter content) are easier to obtain and have been used more frequently to assess plant performance (Cornelissen et al 2003;Lavorel and Garnier 2002).…”

Root quality and decomposition environment, but not tree species richness, drive root decomposition in tropical forests

“…The study was conducted in two experimental forest sites in central Panama, Sardinilla (9°19′ N, 79°38′ W) and Agua Salud (9°13′ N, 79°47′ W), with annual precipitation of 2350 mm and 2300 mm, respectively van Breugel et al 2013). The Sardinilla site is a long-term diversity experiment consisting of a forest planted in 2001 on former pasture land with either one, three or six native tree species (Scherer-Lorenzen et al 2005).…”

Challenges of Governing Second-Growth Forests: A Case Study from the Brazilian Amazonian State of Pará

“…Yet, second-growth forests can often be highly ephemeral components of a landscape [13]. Many human-modified landscapes in agricultural frontier regions are comprised of complex and dynamic patchworks of agricultural areas and fragments of regenerating forest [14].…”