Using GEDI lidar data and airborne laser scanning to assess height growth dynamics in fast-growing species: a showcase in Spain

Adrián Pascual,Juan Guerra-Hernández

doi:10.1186/s40663-021-00291-2

Adrián Pascual, Juan Guerra-Hernández

Open Access

https://doi.org/10.1186/s40663-021-00291-2

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Journal: Forest Ecosystems	Publication Date: Feb 19, 2021
Citations: 21	License type: open-access

Affiliation: Arizona State University, University of Lisbon

Abstract

BackgroundThe NASA’s Global Ecosystem Dynamics Investigation (GEDI) satellite mission aims at scanning forest ecosystems on a multi-temporal short-rotation basis. The GEDI data can validate and update statistics from nationwide airborne laser scanning (ALS). We present a case in the Northwest of Spain using GEDI statistics and nationwide ALS surveys to estimate forest dynamics in three fast-growing forest ecosystems comprising 211,346 ha. The objectives were: i) to analyze the potential of GEDI to detect disturbances, ii) to investigate uncertainty source regarding non-positive height increments from the 2015–2017 ALS data to the 2019 GEDI laser shots and iii) to estimate height growth using polygons from the Forest Map of Spain (FMS). A set of 258 National Forest Inventory plots were used to validate the observed height dynamics.ResultsThe spatio-temporal assessment from ALS surveying to GEDI scanning allowed the large-scale detection of harvests. The mean annual height growths were 0.79 (SD = 0.63), 0.60 (SD = 0.42) and 0.94 (SD = 0.75) m for Pinus pinaster, Pinus radiata and Eucalyptus spp., respectively. The median annual values from the ALS-GEDI positive increments were close to NFI-based growth values computed for Pinus pinaster and Pinus radiata, respectively. The effect of edge border, spatial co-registration of GEDI shots and the influence of forest cover in the observed dynamics were important factors to considering when processing ALS data and GEDI shots.DiscussionThe use of GEDI laser data provides valuable insights for forest industry operations especially when accounting for fast changes. However, errors derived from positioning, ground finder and canopy structure can introduce uncertainty to understand the detected growth patterns as documented in this study. The analysis of forest growth using ALS and GEDI would benefit from the generalization of common rules and data processing schemes as the GEDI mission is increasingly being utilized in the forest remote sensing community.

Highlights

Forest inventories employing airborne laser scanning (ALS) data have become common in many countries (Wehr and Lohr 1999; Lefsky et al 2002; Næsset et al 2004; White et al 2016)
The impact of ALS data is strong on forest decision-making when data from National Forest Inventories is estimated with remote sensing sources under good co-registration goodness (Pascual et al 2019)
The objectives of this study were: i) to use Global Ecosystem Dynamics Investigation (GEDI) to detect disturbances at regional level, ii) to investigate, evaluate and explain the source of uncertainty when interpreting GEDI footprint ground shots and iii) to validate the height growth dynamics detected from ALS to GEDI compared to ground National Forest Inventories (NFI) data

Summary

Introduction

Forest inventories employing airborne laser scanning (ALS) data have become common in many countries (Wehr and Lohr 1999; Lefsky et al 2002; Næsset et al 2004; White et al 2016). The number of countries that have been scanned at least once relying on ALS technology has increased and in many areas forest dynamics and natural disturbances can be estimated using multitemporal LiDAR (Hopkinson et al 2008). The GEDI data can validate and update statistics from nationwide airborne laser scanning (ALS). We present a case in the Northwest of Spain using GEDI statistics and nationwide ALS surveys to estimate forest dynamics in three fast-growing forest ecosystems comprising 211,346 ha. The objectives were: i) to analyze the potential of GEDI to detect disturbances, ii) to investigate uncertainty source regarding non-positive height increments from the 2015–2017 ALS data to the 2019 GEDI laser shots and iii) to estimate height growth using polygons from the Forest Map of Spain (FMS). A set of 258 National Forest Inventory plots were used to validate the observed height dynamics

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