Forest Canopy Heights in the Pacific Northwest Based on InSAR Phase Discontinuities across Short Spatial Scales

Veronica Prush,Rowena Lohman

doi:10.3390/rs6043210

Veronica Prush, Rowena Lohman

Open Access

https://doi.org/10.3390/rs6043210

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Journal: Remote sensing	Publication Date: Apr 10, 2014
Citations: 52	License type: CC BY 3.0

Affiliation: Cornell University

Abstract

Rapid land use changes are substantially altering the global carbon budget, yet quantifying the impact of these changes, or assessing efforts to mitigate them, remains challenging. Methods for assessing forest carbon range from precise ground surveys to remote-sensing approaches that provide proxies for canopy height and structure. We introduce a method for extracting a proxy for canopy heights from Interferometric Synthetic Aperture Radar (InSAR) data. Our method focuses on short-spatial scale differences between forested and cleared regions, reducing the impact of errors from variations in atmospheric water vapor or satellite orbital positions. We generate time-varying, Landsat-based maps of land use and perform our analysis on the original wrapped (modulo-2π) data to avoid errors introduce by phase unwrapping and to allow assessment of the confidence of our results (within 3–4 m in many cases). We apply our approach to the Pacific Northwest, which contains some of the world’s tallest trees and has experienced extensive clearcutting. We use SAR imagery acquired at L-band by the PALSAR instrument on the Japanese Aerospace Exploration Agency’s (JAXA) Advanced Land Observation Satellite (ALOS). As SAR data archives expand, our approach can complement other remote-sensing methods and allow time-variable assessment of forest carbon budgets worldwide.

Highlights

The contribution of ongoing global deforestation to climate change has been of increasing concern over the past few decades (e.g., [1,2,3])
Many of the statistics on global forests depend on the self-reporting of nations, making them subject to the ability and desire of a nation to accurately report on its forest inventory [4]
We compare our results between overlapping Interferometric Synthetic Aperture Radar (InSAR) tracks with completely independent sets of SAR imagery and demonstrate that the inferred heights are consistent within our stated errors

Summary

Introduction

The contribution of ongoing global deforestation to climate change has been of increasing concern over the past few decades (e.g., [1,2,3]). An estimated 650 billion metric tons of carbon are stored in forests globally, more than is present in the atmosphere [4]. 12% of anthropogenic greenhouse gas emissions can be attributed to CO2 emitted as a result of deforestation [5]. Any legislation that seeks to curb deforestation rates must be accompanied by a means for verifying compliance and taking inventories of current forest stocks. Such inventories allow assessment of the efficacy of forest management practices and monitoring of overall forest health. Many of the statistics on global forests depend on the self-reporting of nations, making them subject to the ability and desire of a nation to accurately report on its forest inventory [4]

Methods

Results

Conclusion