August 14, 2023

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Optical Satellite Sensitivity to Estimates of Windthrow Tree Mortality in Tropical Forests

Interplay of turbulence regimes, deep convection, and tree mortality in a Central Amazon Rainforest.

A windthrown forest located near Manaus, Central Amazon, Brazil, and inventory and virtual plots used to quantify tree mortality (left). Distribution of windthrow tree mortality from field subplots and satellite data with varying spatial resolution (right).

[Reprinted under a Creative Commons Attribution 4.0 International License (CC BY 4.0) from Emmert, L., et al. "Sensitivity of Optical Satellites to Estimate Windthrow Tree-Mortality in a Central Amazon Forest." Remote Sensing 15 (16), 4027 (2023). DOI:10.3390/rs15164027.]

The Science

Remote sensing estimates of windthrow tree mortality were produced from Spectral Mixture Analysis and evaluated with forest inventory data (i.e., ground true) by using Generalized Linear Models. Field-measured windthrow tree mortality (3 20m x 125m transects and 30 10m x 25m subplots) crossing the entire disturbance gradient was 26.9 ± 11.1% (mean ± 95% CI).

The Impact

Although the three satellites produced reliable and statistically similar estimates (from 26.5% to 30.3%, p < 0.001), Landsat 8 had the most accurate results and efficiently captured field-observed variations in windthrow tree -mortality across the entire gradient of disturbance. (Sentinel 2 and WorldView 2 produced the second and third best results, respectively). As expected, mean-associated uncertainties decreased systematically with increasing spatial resolution (i.e., from Landsat 8 to Sentinel 2 and WorldView 2).

Summary

Although satellites with high spatial resolution have become available in the last decade, they have not yet been employed for the quantification of windthrow tree mortality. This study addresses how increasing satellites’ spatial resolution affects plot-to-landscape estimates of windthrow tree mortality. Researchers combined forest inventory data with Landsat 8 (30 m pixel), Sentinel 2 (10 m), and WorldView 2 (2 m) imagery over an old-growth forest in the Central Amazon that was disturbed by a single windthrow event in November 2015.

Principal Investigator

Robinson Negron-Juarez
Lawrence Berkeley National Laboratory
[email protected]

Program Manager

Brian Benscoter
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
[email protected]

Funding

This research was supported by the U.S. Department of Energy’s Office of Science Biological and Environmental Research (BER) program, Agreement grant DE-AC02-05CH11231, Next-Generation Ecosystem Experiments-Tropics (NGEE-Tropics). This research is part of the INVENTA (Interação Vento-Árvore na Amazônia), and ATTO projects funded by the German Federal Ministry of Education and Research (BMBF contracts no. 01LB1001A and no. 01LK1602A), the Brazilian Ministry of Science, Technology, and Innovation (MCTI/FINEP contract no. 01.11.01248.00), and the Max Planck Society (MPG). Funding was also received from the Amazonas State Research Support Foundation (FAPEAM) (PhD grant no. 41640.UNI739.1607.28032019-65939) and the Instituto Nacional de Ciência e Tecnologia (INCT) Madeiras da Amazônia.

References

Emmert, L., et al. "Sensitivity of Optical Satellites to Estimate Windthrow Tree-Mortality in a Central Amazon Forest." Remote Sensing 15 (16), 4027  (2023). https://doi.org/10.3390/rs15164027.