Disturbance Regimes Drive The Diversity of Regional Floristic Pools Across Guianan Rainforest Landscapes

Stéphane Guitet,Gaëlle Jaouen,Pierre Couteron,Raphaël Pélissier,Bruno Hérault,Cécile Richard-Hansen,Vincent Freycon,Jean-François Molino,Sophie Gonzalez,Olivier Brunaux,Grégoire Vincent,Thomas Denis,Daniel Sabatier

doi:10.1038/s41598-018-22209-9

Abstract

Disturbances control rainforest dynamics, and, according to the intermediate disturbance hypothesis (IDH), disturbance regime is a key driver of local diversity. Variations in disturbance regimes and their consequences on regional diversity at broad spatiotemporal scales are still poorly understood. Using multidisciplinary large-scale inventories and LiDAR acquisitions, we developed a robust indicator of disturbance regimes based on the frequency of a few early successional and widely distributed pioneer species. We demonstrate at the landscape scale that tree-species diversity and disturbance regimes vary with climate and relief. Significant relationships between the disturbance indicator, tree-species diversity and soil phosphorus content agree with the hypothesis that rainforest diversity is controlled both by disturbance regimes and long-term ecosystem stability. These effects explain the broad-scale patterns of floristic diversity observed between landscapes. In fact, species-rich forests in highlands, which have benefited from long-term stability combined with a moderate and regular regime of local disturbances, contrast with less diversified forests on recently shaped lowlands, which have undergone more recent changes and irregular dynamics. These results suggest that taking the current disturbance regime into account and including geomorphological stratifications in climate-vegetation models may be an effective way to improve the prediction of changes in species diversity under climate change.

Highlights

Disturbances control rainforest dynamics, and, according to the intermediate disturbance hypothesis (IDH), disturbance regime is a key driver of local diversity
Applying Bayesian averaging models to the entire dataset or to a subsample of 21 sites for which complete soil analyses were available, we found that disturbance (DI approximated by Urticaceae frequency) was a more important factor than habitat diversity (HD approximated by soil diversity, mean slope, elevation range), resource availability (RA approximated by soil properties), or long-term climatic stability (LS approximated by rainfall, elevation and geographical coordinates) in explaining tree diversity
We found a new indicator of disturbance regimes, relative frequency of Urticaceae trees, which is highly correlated with wood specific gravity and canopy gaps fraction from LiDAR, but much easier to implement at large scale

Summary

Introduction

Disturbances control rainforest dynamics, and, according to the intermediate disturbance hypothesis (IDH), disturbance regime is a key driver of local diversity. Significant relationships between the disturbance indicator, tree-species diversity and soil phosphorus content agree with the hypothesis that rainforest diversity is controlled both by disturbance regimes and long-term ecosystem stability These effects explain the broad-scale patterns of floristic diversity observed between landscapes. Stropp and colleagues[13] inferred from wood density data across a network of 1-ha forest plots in Amazonia, that the frequency of disturbances was the main process driving local diversity, but not regional diversity, which they found more correlated to proxies of paleoclimatic stability and long-term ecosystem dynamics These findings suggest that both local- and large-scale spatio-temporal dynamic processes interact in shaping the current pattern of www.nature.com/scientificreports/. Geospatial data were used to account for environmental drivers of regional diversity such as rainfall[13] or geomorphology[17], which have already shown to be explanatory of broad scale floristic patterns in French Guiana[18,19]

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Conclusion