Edaphic factors and initial conditions influence successional trajectories of early regenerating tropical dry forests

Sergio Estrada‐Villegas,Trevor Caughlin,Mario Bailón,Stefan A Schnitzer,Michiel Van Breugel,Jefferson S Hall,Benjamin L Turner,Cynthia Chang

doi:10.1111/1365-2745.13263

Abstract

Abstract Edaphic factors and initial conditions can regulate the speed of forest succession. Edaphic factors, which include soil chemistry and topography, determine soil resource availability and can filter species as forests mature. Initial plant cover early in succession can determine the rates at which secondary forests change in structure, richness, biomass and composition over time. While some of the effects of edaphic factors and initial conditions on forest succession have been studied, how they simultaneously modify young regenerating tropical forest has rarely been examined. We surveyed 22 young forests plots in Panama for 7 years (11, 6 and 3‐year‐old stands when censuses began). We study how tree and liana species composition change early in succession, as well as how edaphic factors (soil nutrients and topography) and initial conditions (initial basal area and forest canopy cover) influence changes in tree and liana abundance, species richness, biomass and composition throughout succession. We found that edaphic factors and initial conditions explained up to 45% of the variation in the successional trajectories for trees and lianas. Soil nutrients had a significant positive effect on the changes in tree biomass accretion, while topography significantly contributed to community similarity of large lianas over time. Initial basal area had a significant negative effect on the changes in sapling abundance and tree richness over time and a positive marginal effect on tree biomass accretion. Forest canopy cover only had a positive marginal effect on changes in sapling abundance. Tree abundance, biomass and richness increased over time, while sapling abundance, biomass and richness remained stable or decreased, probably due to community thinning. However, changes over time of small and large lianas diverged, probably due to differential resource availability that affected lianas but not trees. Synthesis. Soil fertility, topography and initial basal area influence early forest regeneration. Higher soil fertility can allow trees to fix carbon faster, and lianas might show habitat association to ridges and slopes. Basal area can determine how fast saplings and trees change in abundance, richness and biomass over time by possibly affecting space availability for recruitment and light availability for growth.

Highlights

One of the main goals in forest ecology is to understand the main drivers that shape successional trajectories (Meiners, Cadotte, Fridley, Pickett, & Walker, 2015)
Our results show that high initial basal area early in succession decreased the rate of change at which saplings are recruited, sapling biomass is accumulated and species are added to the forest
Our results show that the variability of initial conditions, as reflected by different initial basal areas across plots, may affect the rates of change of young successional tropical dry forests

Summary

Introduction

One of the main goals in forest ecology is to understand the main drivers that shape successional trajectories (Meiners, Cadotte, Fridley, Pickett, & Walker, 2015). Edaphic factors, which include soil chemistry, soil texture and topography, may have strong and deterministic effects on community composition. Availability of different levels of soil resources can filter out species as communities assemble throughout succession, creating predictable changes in forest composition (Powers & Marín‐Spiotta, 2017). Initial conditions represent the amount of vegetation present across sites during early stages of forest succession (Donato, Campbell, & Franklin, 2012; Parker & Pickett, 1998; Phillips, 2004). Initial conditions across sites can influence succession in contrasting ways compared to edaphic conditions, especially if sites are abandoned at similar times. Initial conditions such as vegetation remnants can speed community recovery via seed dispersal or facilitation regardless of the edaphic conditions across sites

Methods

Results

Discussion

Conclusion