Early Regeneration of Tropical Dry Forest from Abandoned Pastures: Contrasting Chronosequence and Dynamic Approaches

Abstract

Old field secondary succession of tropical dry forests (TDFs) is poorly understood, particularly regarding the dynamics of seedlings, saplings, and sprouts (regenerative communities). We used chronosequence and dynamic approaches to: (1) document successional trajectories of regenerative communities during the first dozen years of regeneration in abandoned pastures at Chamela, Mexico; (2) test the usefulness of chronosequences to predict the dynamics of regenerative communities along time; and (3) assess the influence of surrounding forest matrix, stand density, and understory light availability (in the rainy season) as driving factors of such dynamics. More than 1000 plants and 95 species of shrubs and trees 10-100 cm tall were monitored between 2004 and 2007 in nine abandoned pastures (0-12 yr since abandonment) and two old-growth forest (OGF) sites; gain and loss rates of plants, species, and plant cover were obtained. Chronosequence predicted a rapid and asymptotic increase of plant density, species density, and plant cover toward the OGF values. Such prediction did not match with dynamic data that showed negative or neutral net community rates of change, independently of fallow age. Recruitment and species gain rates increased with the amount surrounding forest matrix. No other effect of the explored factors was detected. Strong rainfall shortenings could be responsible for the high loss and low gain rates of plants and species recorded in most sites. We highlight the critical role of supra-annual rainfall variability on the dynamics of TDF regenerative communities and the poor predictive value of chronosequences in forest systems subjected to strong environmental temporal variation.Abstract in Spanish is available at http://www.blackwell-synergy.com/loi/btp.

Effects of livestock management on the supply of ecosystem services in pastures in a tropical dry region of western Mexico

“…Also, they reduce the dominance of introduced grasses and promote seedling emergence (Lloret, 1998). Greater forest cover in the surrounding matrix has been associated to increased seedling recruitment (both in terms of species richness and number of individuals) in this region (Maza-Villalobos et al, 2011), as it contributes to higher propagule availability. These effects were orthogonal to those of the management regime components that foster forage production.…”

Root depth and morphology in response to soil drought: comparing ecological groups along the secondary succession in a tropical dry forest

“…This produces a mosaic of vegetation patches comprising different ages of recovery ranging from 0 to 15 years as well as patches of old-growth forest. Based on extensive vegetation surveys conducted across a chronosequence in the region (Maza-Villalobos et al 2011;Ramos-López 2012), we classified our 23 study species into three successional status categories: early successional species, comprising specialists of the early successional stages (0-5 years of abandonment); mid-successional species, taxa entering the succession during intermediate stages of vegetation development (8-15 years of abandonment); and old-growth forest species, comprising taxa that successfully establish in late to old-growth forest but not in the early sites. The numbers and identities of species belonging to each successional group are shown in the Electronic Supplementary Material (Table S1).…”

Effects of ENSO and Temporal Rainfall Variation on the Dynamics of Successional Communities in Old-Field Succession of a Tropical Dry Forest

“…In a previous paper [41] we analysed successional patterns of these communities, which strongly suggested that temporal variation in rainfall plays a critical role in such dynamics. In that paper we showed that the observed patterns had no relation at all with understory light availability or with structural variables of the established woody communities (trees and shrubs with DBH ≥1 cm).…”