Relative Efficiency of ALS and InSAR for Biomass Estimation in a Tanzanian Rainforest

Endre Hansen,Annika Kangas,Terje Gobakken,Svein Solberg,Liviu Ene,Ernest Mauya,Erik Næsset

doi:10.3390/rs70809865

Abstract

Forest inventories based on field sample surveys, supported by auxiliary remotely sensed data, have the potential to provide transparent and confident estimates of forest carbon stocks required in climate change mitigation schemes such as the REDD+ mechanism. The field plot size is of importance for the precision of carbon stock estimates, and better information of the relationship between plot size and precision can be useful in designing future inventories. Precision estimates of forest biomass estimates developed from 30 concentric field plots with sizes of 700, 900, …, 1900 m2, sampled in a Tanzanian rainforest, were assessed in a model-based inference framework. Remotely sensed data from airborne laser scanning (ALS) and interferometric synthetic aperture radio detection and ranging (InSAR) were used as auxiliary information. The findings indicate that larger field plots are relatively more efficient for inventories supported by remotely sensed ALS and InSAR data. A simulation showed that a pure field-based inventory would have to comprise 3.5–6.0 times as many observations for plot sizes of 700–1900 m2 to achieve the same precision as an inventory supported by ALS data.

Highlights

Forest inventories provide information for management of forest resources on national, district, and local levels
The findings in the present study demonstrate the impact of the size of the field plots on the precision of biomass estimates using two types of three-dimensional remotely sensed data
terrain elevation (TE) models showed a positive correlation between biomass and elevation, and the explanatory variable was increasingly significant from p = 0.044 at 700 m2 to p = 0.002 at 1900 m2

Summary

Introduction

Forest inventories provide information for management of forest resources on national, district, and local levels. Over the past decade the role of forests has shifted from a source of timber and non-timber products, to a source of a wide array of ecosystem services. One such service is the forests’ role in global climate change mitigation, and the development of a marked-based mechanism to value this service has resulted in what is known as the REDD+ mechanism. (reducing emissions from deforestation and forest degradation, conservation and enhancement of forest carbon stocks, and sustainable management of forests in developing countries), described in the 16th session of the Conference of Parties to the United Nations Framework Convention on Climate. Forest inventories have the potential to provide transparent and confident estimates of forest carbon stocks needed in such systems

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