Apparent environmental synergism drives the dynamics of Amazonian forest fragments

Abstract

Abstract. Many contemporary ecosystems are likely to be affected by multiple environmental drivers, complicating efforts to predict future changes in those ecosystems. We studied long-term changes in forest dynamics and liana (woody vine) abundance and biomass in fragmented and intact forests of the central Amazon. We did so by contrasting trends in 33 permanent 1-ha plots near forest edges (plot center ,100 m from the nearest edge) with those in 36 1-ha plots in intact-forest interiors (150-3300 m from nearest edge). In fragmented and edge-affected forests, rates of tree (!10 cm diameter at breast height) mortality and recruitment were often sharply elevated, especially in the first 10-15 years after fragmentation. Lianas (!2 cm stem diameter) also increased markedly in abundance (mean 6 SD ¼ 1.78 6 1.23% per yr) and biomass (1.30 6 1.39% per yr) over time, especially in plots with high edge-related tree mortality. However, plots in undisturbed forest interiors, which were originally established as experimental controls, also experienced long-term changes. In these plots, tree mortality and recruitment rose significantly over time, as did liana abundance (1.00 6 0.88% per yr) and biomass (0.32 6 1.37% per yr). These changes were smaller in magnitude than those in fragments but were nonetheless concerted in nature and highly statistically significant. The causes of these changes in forest interiors are unknown, but are broadly consistent with those expected from rising atmospheric CO 2 or regional climate drivers that influence forest dynamics. Hence, the dynamics of Amazonian forest fragments cannot be understood simply as a consequence of forest fragmentation. Rather, the changes we observed appear to arise from an interaction of fragmentation with one or more global-or regional-scale drivers affecting forest dynamics. Both sets of phenomena are evidently increasing forest dynamics and liana abundances in fragmented forests, changes that could reduce carbon storage and alter many aspects of forest ecology.

Stability in a changing world – palm community dynamics in the hyperdiverse western Amazon over 17 years

“…For instance, Laurance et al . () monitored 69 1‐ha permanent plots in forest edges and preserved forest interiors in the central Amazon from 1980 to 2012. They showed that mortality and recruitment of trees and lianas in edge and forest interiors have accelerated over time.…”

Under the radar: mitigating enigmatic ecological impacts

“…In the Amazon basin, increased fire incidence, decreased carbon storage, and changes in forest dynamics caused by logging and fragmentation of forests are amplified by changes in the climate, with potential for dangerous feedback between impacts [26,77,78]. [2,79].…”

Assessing Species Vulnerability to Climate Change in Tropical Asia: Implications for Biodiversity Conservation and Forest Management

“…In the Amazon Basin where climate change is already having an impact, rising atmospheric CO2 and regional climate drivers influence forest fragments dynamics, tree community composition and distribution, tree mortality and aboveground biomass (Laurance et al 2014;Olivares et al 2015;Raghunathan et al 2015). Disturbances, such as hurricanes, cyclones, or typhoons, significantly affect forest structure and species composition in Central America (Anadoʹn et al 2014;Shiels & Gonzalez 2014;.…”

“…The majority of the studies focussed on South and Central America (n=26) followed by South Asia (n=24) and Africa (n=15) ( Miles et al 2004;Saatchi et al 2008); (2) changes in forest stand dynamics, including changes in forest cover, structure and composition (e.g., Anadoʹn et al 2014;Laurance et al 2014); and (3) changes in tree phenology (Gunarathne & Perera 2014;Hopkins & Graham 1987;Numata et al 2003). The temporal trend of publications indicates that climate change research in all tropical regions has increased over the last decade (Figure 2.2).…”

“…In the Brazilian Amazon, climate change is responsible for shifts in tree species composition (Raghunathan et al 2015) and changes in liana abundance and biomass (Fearnside 2004;Laurance et al 2014). Malhi et al (2009), in a study on climate change induced dieback of Amazon rainforest, found that dry-season water stress caused by high temperature is likely to increase in Amazonia over the 21st century.…”