Allometric equations for integrating remote sensing imagery into forest monitoring programmes.

Tommaso Jucker,Frans Bongers,Cécile Antin,David I Forrester,Matthias Haeni,Anna T Trugman,Hannsjörg Wöll,Jérôme Chave,Frank J Sterck,Nicolas Barbier,Steven I Higgins,Wenhua Xiang,Niklaus E Zimmermann,Glenn R Moncrieff,Peter Waldner,Robert J Holdaway,David A Coomes,Pierre Ploton,Mark C Vanderwel,Karin Y Van Ewijk,Michele Dalponte,Lourens Poorter,Bonaventure Sonké,Michael Schlund,Murray Woods,Christian Wirth,John P Caspersen ,Craig G Lorimer ,B M M Wedeux ,Stéphane Momo Takoudjou ,Yoshihiro Iida ,Vladimir А Usoltsev ,Peter Marshall ,K Abd Rahman

doi:10.1111/gcb.13388

Abstract

Remote sensing is revolutionizing the way we study forests, and recent technological advances mean we are now able – for the first time – to identify and measure the crown dimensions of individual trees from airborne imagery. Yet to make full use of these data for quantifying forest carbon stocks and dynamics, a new generation of allometric tools which have tree height and crown size at their centre are needed. Here, we compile a global database of 108753 trees for which stem diameter, height and crown diameter have all been measured, including 2395 trees harvested to measure aboveground biomass. Using this database, we develop general allometric models for estimating both the diameter and aboveground biomass of trees from attributes which can be remotely sensed – specifically height and crown diameter. We show that tree height and crown diameter jointly quantify the aboveground biomass of individual trees and find that a single equation predicts stem diameter from these two variables across the world's forests. These new allometric models provide an intuitive way of integrating remote sensing imagery into large‐scale forest monitoring programmes and will be of key importance for parameterizing the next generation of dynamic vegetation models.

Highlights

Forests are a key component of the terrestrial carbon cycle (Beer et al, 2010; Pan et al, 2011), making forest conservation of critical importance for mitigating climate change (Agrawal et al, 2011)
We aim to develop allometric equations for estimating a tree’s diameter and aboveground biomass based on attributes which can be remotely sensed – namely tree height and crown diameter – enabling airborne imagery to be fully integrated into existing carbon monitoring programmes (Fig. 1)
We developed general allometric models for estimating both the stem diameter and aboveground biomass of trees based on crown architectural properties which can be remotely sensed: tree height and crown diameter

Summary

Introduction

Forests are a key component of the terrestrial carbon cycle (Beer et al, 2010; Pan et al, 2011), making forest conservation of critical importance for mitigating climate change (Agrawal et al, 2011). Airborne laser scanning (ALS) is promising in this regard (Asner & Mascaro, 2014; Asner et al, 2014), allowing the 3D structure of entire forest landscapes to be reconstructed in detail using highfrequency laser scanners mounted on airplanes or unmanned aerial vehicles Advances in both sensor technology and computation mean we are able – for the first time – to reliably identify and measure the crown dimensions of individual trees using ALS (Yao et al, 2012; Duncanson et al, 2014; Shendryk et al, 2016), marking a fundamental shift in the way we census forests. We aim to develop allometric equations for estimating a tree’s diameter and aboveground biomass based on attributes which can be remotely sensed – namely tree height and crown diameter – enabling airborne imagery to be fully integrated into existing carbon monitoring programmes (Fig. 1)

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Conclusion