Understanding ‘saturation’ of radar signals over forests

Abstract There is an urgent need to quantify anthropogenic influence on forest carbon stocks. Using satellite-based radar imagery for such purposes has been challenged by the apparent loss of signal sensitivity to changes in forest aboveground volume (AGV) above a certain ‘saturation’ point. The cau...

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Autores principales:	Neha Joshi, Edward T. A. Mitchard, Matthew Brolly, Johannes Schumacher, Alfredo Fernández-Landa, Vivian Kvist Johannsen, Miguel Marchamalo, Rasmus Fensholt
Formato:	article
Lenguaje:	EN
Publicado:	Nature Portfolio 2017
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/a98530f084b642e89bfb94a730db05f9
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spelling	oai:doaj.org-article:a98530f084b642e89bfb94a730db05f92021-12-02T16:05:57ZUnderstanding ‘saturation’ of radar signals over forests10.1038/s41598-017-03469-32045-2322https://doaj.org/article/a98530f084b642e89bfb94a730db05f92017-06-01T00:00:00Zhttps://doi.org/10.1038/s41598-017-03469-3https://doaj.org/toc/2045-2322Abstract There is an urgent need to quantify anthropogenic influence on forest carbon stocks. Using satellite-based radar imagery for such purposes has been challenged by the apparent loss of signal sensitivity to changes in forest aboveground volume (AGV) above a certain ‘saturation’ point. The causes of saturation are debated and often inadequately addressed, posing a major limitation to mapping AGV with the latest radar satellites. Using ground- and lidar-measurements across La Rioja province (Spain) and Denmark, we investigate how various properties of forest structure (average stem height, size and number density; proportion of canopy and understory cover) simultaneously influence radar backscatter. It is found that increases in backscatter due to changes in some properties (e.g. increasing stem sizes) are often compensated by equal magnitude decreases caused by other properties (e.g. decreasing stem numbers and increasing heights), contributing to the apparent saturation of the AGV-backscatter trend. Thus, knowledge of the impact of management practices and disturbances on forest structure may allow the use of radar imagery for forest biomass estimates beyond commonly reported saturation points.Neha JoshiEdward T. A. MitchardMatthew BrollyJohannes SchumacherAlfredo Fernández-LandaVivian Kvist JohannsenMiguel MarchamaloRasmus FensholtNature PortfolioarticleMedicineRScienceQENScientific Reports, Vol 7, Iss 1, Pp 1-11 (2017)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Neha Joshi Edward T. A. Mitchard Matthew Brolly Johannes Schumacher Alfredo Fernández-Landa Vivian Kvist Johannsen Miguel Marchamalo Rasmus Fensholt Understanding ‘saturation’ of radar signals over forests
description	Abstract There is an urgent need to quantify anthropogenic influence on forest carbon stocks. Using satellite-based radar imagery for such purposes has been challenged by the apparent loss of signal sensitivity to changes in forest aboveground volume (AGV) above a certain ‘saturation’ point. The causes of saturation are debated and often inadequately addressed, posing a major limitation to mapping AGV with the latest radar satellites. Using ground- and lidar-measurements across La Rioja province (Spain) and Denmark, we investigate how various properties of forest structure (average stem height, size and number density; proportion of canopy and understory cover) simultaneously influence radar backscatter. It is found that increases in backscatter due to changes in some properties (e.g. increasing stem sizes) are often compensated by equal magnitude decreases caused by other properties (e.g. decreasing stem numbers and increasing heights), contributing to the apparent saturation of the AGV-backscatter trend. Thus, knowledge of the impact of management practices and disturbances on forest structure may allow the use of radar imagery for forest biomass estimates beyond commonly reported saturation points.
format	article
author	Neha Joshi Edward T. A. Mitchard Matthew Brolly Johannes Schumacher Alfredo Fernández-Landa Vivian Kvist Johannsen Miguel Marchamalo Rasmus Fensholt
author_facet	Neha Joshi Edward T. A. Mitchard Matthew Brolly Johannes Schumacher Alfredo Fernández-Landa Vivian Kvist Johannsen Miguel Marchamalo Rasmus Fensholt
author_sort	Neha Joshi
title	Understanding ‘saturation’ of radar signals over forests
title_short	Understanding ‘saturation’ of radar signals over forests
title_full	Understanding ‘saturation’ of radar signals over forests
title_fullStr	Understanding ‘saturation’ of radar signals over forests
title_full_unstemmed	Understanding ‘saturation’ of radar signals over forests
title_sort	understanding ‘saturation’ of radar signals over forests
publisher	Nature Portfolio
publishDate	2017
url	https://doaj.org/article/a98530f084b642e89bfb94a730db05f9
work_keys_str_mv	AT nehajoshi understandingsaturationofradarsignalsoverforests AT edwardtamitchard understandingsaturationofradarsignalsoverforests AT matthewbrolly understandingsaturationofradarsignalsoverforests AT johannesschumacher understandingsaturationofradarsignalsoverforests AT alfredofernandezlanda understandingsaturationofradarsignalsoverforests AT viviankvistjohannsen understandingsaturationofradarsignalsoverforests AT miguelmarchamalo understandingsaturationofradarsignalsoverforests AT rasmusfensholt understandingsaturationofradarsignalsoverforests
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Understanding ‘saturation’ of radar signals over forests

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