Optimizing the Remote Detection of Tropical Rainforest Structure with Airborne Lidar: Leaf Area Profile Sensitivity to Pulse Density and Spatial Sampling

Author(s)

Alves de Almeida, Danilo Roberti ^[1] ; Stark, Scott C. ^[2] ; Shao, Gang ^[2] ; Schietti, Juliana ^[3] ; Nelson, Bruce Walker ^[3] ; Silva, Carlos Alberto ^[4] ; Gorgens, Eric Bastos ^[5] ; Valbuena, Ruben ^{[6, 7]} ; Papa, Daniel de Almeida ^{[1, 8]} ; Santin Brancalion, Pedro Henrique ^[1]

Affiliation

^[1] Univ Sao Paulo, ESALQ, Luiz de Queiroz Coll Agr, Dept Forest Sci, Av Padua Dias 11, BR-13418900 Piracicaba - Brazil

^[2] Michigan State Univ, Dept Forestry, E Lansing, MI 48824 - USA

^[3] Natl Inst Amazon Res INPA, Av Andre Araujo 2936, BR-69067375 Manaus, Amazonas - Brazil

^[4] US Forest Serv, USDA, RMRS, 1221 South Main St, Moscow, ID 83843 - USA

^[5] Fed Univ Vales Jequitinhonha & Mucuri Campus JK, Dept Forestry, Rodovia MGT 367 Km 583, 5000, BR-69900056 Teofilo Otoni - Brazil

^[6] Univ Cambridge, Dept Plant Sci Forest Ecol & Conservat, Downing St, Cambridge CB2 3EA - England

^[7] Univ Eastern Finland, Sch Forest Sci, POB 111, Joensuu - Finland

^[8] Embrapa Acre, Rodovia BR 364, Km 14, BR-69900056 Rio Branco - Brazil

• Document type: Journal article
• Source: REMOTE SENSING; v. 11, n. 1 JAN 1 2019.
• Web of Science Citations: 13

Abstract

Airborne Laser Scanning (ALS) has been considered as a primary source to model the structure and function of a forest canopy through the indicators leaf area index (LAI) and vertical canopy profiles of leaf area density (LAD). However, little is known about the effects of the laser pulse density and the grain size (horizontal binning resolution) of the laser point cloud on the estimation of LAD profiles and their associated LAIs. Our objective was to determine the optimal values for reliable and stable estimates of LAD profiles from ALS data obtained over a dense tropical forest. Profiles were compared using three methods: Destructive field sampling, Portable Canopy profiling Lidar (PCL) and ALS. Stable LAD profiles from ALS, concordant with the other two analytical methods, were obtained when the grain size was less than 10 m and pulse density was high (>15 pulses m(-2)). Lower pulse densities also provided stable and reliable LAD profiles when using an appropriate adjustment (coefficient K). We also discuss how LAD profiles might be corrected throughout the landscape when using ALS surveys of lower density, by calibrating with LAI measurements in the field or from PCL. Appropriate choices of grain size, pulse density and K provide reliable estimates of LAD and associated tree plot demography and biomass in dense forest ecosystems. (AU)

• FAPESP's process: 17/03867-6 - Towards universal biological structural assessment of forests with LiDAR remote sensing for vegetation monitoring in a changing world
• Grantee: Danilo Roberti Alves de Almeida
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• FAPESP's process: 16/05219-9 - Monitoring forest landscape restoration through Light Detection and Ranging (LiDAR).
• Grantee: Danilo Roberti Alves de Almeida
• Support Opportunities: Scholarships in Brazil - Doctorate