Large-scale variations in the dynamics of Amazon forest canopy gaps from airborne lidar data and opportunities for tree mortality estimates

Author(s)

Dalagnol, Ricardo ^[1] ; Wagner, Fabien H. ^{[2, 1]} ; Galvao, Lenio S. ^[1] ; Streher, Annia S. ^[1] ; Phillips, Oliver L. ^[3] ; Gloor, Emanuel ^[3] ; Pugh, Thomas A. M. ^{[4, 5]} ; Ometto, Jean P. H. B. ^[6] ; Aragao, Luiz E. O. C. ^{[7, 1]}

Affiliation

^[1] Natl Inst Space Res INPE, Earth Observat & Geoinformat Div, BR-12227010 Sao Jose Dos Campos, SP - Brazil

^[2] Fdn Sci Technol & Space Applicat FUNCATE, GeoProc Div, BR-12210131 Sao Jose Dos Campos, SP - Brazil

^[3] Univ Leeds, Sch Geog, Leeds LS2 9JT, W Yorkshire - England

^[4] Univ Birmingham, Sch Geog Earth & Environm Sci, Birmingham B15 2TT, W Midlands - England

^[5] Univ Birmingham, Birmingham Inst Forest Res, Birmingham B15 2TT, W Midlands - England

^[6] Natl Inst Space Res INPE, Earth Syst Sci Ctr, BR-12227010 Sao Jose Dos Campos, SP - Brazil

^[7] Univ Exeter, Coll Life & Environm Sci, Geog, Exeter EX4 4RJ, Devon - England

• Document type: Journal article
• Source: SCIENTIFIC REPORTS; v. 11, n. 1 JAN 14 2021.
• Web of Science Citations: 2

Abstract

We report large-scale estimates of Amazonian gap dynamics using a novel approach with large datasets of airborne light detection and ranging (lidar), including five multi-temporal and 610 single-date lidar datasets. Specifically, we (1) compared the fixed height and relative height methods for gap delineation and established a relationship between static and dynamic gaps (newly created gaps); (2) explored potential environmental/climate drivers explaining gap occurrence using generalized linear models; and (3) cross-related our findings to mortality estimates from 181 field plots. Our findings suggest that static gaps are significantly correlated to dynamic gaps and can inform about structural changes in the forest canopy. Moreover, the relative height outperformed the fixed height method for gap delineation. Well-defined and consistent spatial patterns of dynamic gaps were found over the Amazon, while also revealing the dynamics of areas never sampled in the field. The predominant pattern indicates 20-35% higher gap dynamics at the west and southeast than at the central-east and north. These estimates were notably consistent with field mortality patterns, but they showed 60% lower magnitude likely due to the predominant detection of the broken/uprooted mode of death. While topographic predictors did not explain gap occurrence, the water deficit, soil fertility, forest flooding and degradation were key drivers of gap variability at the regional scale. These findings highlight the importance of lidar in providing opportunities for large-scale gap dynamics and tree mortality monitoring over the Amazon. (AU)

• FAPESP's process: 15/22987-7 - Assessment of climate change impacts on the biomass and carbon dynamics in the Amazon
• Grantee: Ricardo Dal'Agnol da Silva
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 16/17652-9 - Functional diversity of intact and regenerating Amazon, Atlantic Forest and Cerrado systems using hyperspectral imagery
• Grantee: Fabien Hubert Wagner
• Support Opportunities: Scholarships in Brazil - Young Researchers
• FAPESP's process: 15/50484-0 - Functional diversity of intact and regenerating Amazon, Atlantic Forest, and Cerrado systems using hyperspectral imagery
• Grantee: Fabien Hubert Wagner
• Support Opportunities: Research Grants - Young Investigators Grants
• FAPESP's process: 19/21662-8 - Quantifying tree mortality with lasers: using a state-of-the-art model-data fusion approach to estimate biomass loss in tropical forests
• Grantee: Ricardo Dal'Agnol da Silva
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 19/09248-1 - Using deep-learning convolutional network for estimating canopy traits from high-resolution imagery
• Grantee: Annia Susin Streher
• Support Opportunities: Scholarships in Brazil - Technical Training Program - Technical Training