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ABSTRACT Tropical forest dynamics and composition have changed over recent decades, but the proximate drivers of these changes remain unclear. Investigations into these trends have focused on increasing drought stress, CO2, temperature, and fires, whereas convective storms are generally overlooked. We argue that existing literature provides clear support for the importance of storms as drivers of forest change. We reanalyze the largest plot‐based study of tropical forest carbon dynamics to show that lightning frequency—an indicator of storm activity—strongly predicts forest carbon storage and residence time, and its inclusion improves model fit and weakens evidence for the effects of high temperatures. Convective storm activity has increased 5%–25% per decade over the past half century. Extrapolating from historic trends, we estimate that storms likely contribute ca. 50% of the reported increases in biomass mortality across Amazonia, with all realistic combinations of assumptions indicating a possible range of 12%–118%. Spatial variation in storm activity shows weak relationships with drought, demonstrating that forests can experience high drought stress, high storm activity, or both. Accordingly, we hypothesise that convective storms are among the most important drivers of tropical forest change, and as such, they require significant research investment to avoid misguiding science, policy, and management.
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Compositional Acclimation Can Lessen Tropical Forest Change in Response to Increasing Lightning Frequency: Insights From Simulation Modeling
ABSTRACT Lightning frequency in tropical forests has been increasing for decades and lightning is a major agent of forest biomass mortality, but the implications of increased lightning frequency are unclear. Here, we provide a species‐ and spatially explicit implementation of lightning in a mechanistic forest dynamics model. We evaluated the model's ability to reproduce current‐day observations in a Panamanian tropical forest, and the sensitivity of model outputs to plausible changes in lightning frequency. The lightning‐enabled model simulated aboveground biomass (AGB), carbon flux, and stem densities that were consistent with observations. As expected, AGB declined with increasing lightning frequency. However, the magnitude of AGB decline was greatly reduced when trees were assigned empirically derived, species‐specific lightning tolerances. Changes in species composition weakened the sensitivity of AGB to increasing lightning: the AGB of a small number of large‐statured, lightning‐tolerant species increased with increasing lightning frequency. In addition, the effect of lightning on AGB tended to saturate at high lightning frequencies because of the combined effect of changes in size structure and composition. Specifically, the number of large, lightning‐susceptible trees was relatively small at high lightning frequencies. Overall, this study shows that an empirically informed representation of lightning captures the contemporary effects of lightning on forests, indicates that changes in lightning frequency will change forest AGB, species composition, and size structure, and shows that forests can partially acclimate to higher lightning frequency through changes in composition. Thus, more widespread inclusion of the lightning into global ecosystem models would be an important step toward improving simulations of forest responses to global change.
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- PAR ID:
- 10652141
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Global Change Biology
- Volume:
- 31
- Issue:
- 12
- ISSN:
- 1354-1013
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1111/gcb.70635
