Understanding ‘saturation’ of radar signals over forests

Neha Joshi; Edward Mitchard; Matthew Brolly; Johannes Schumacher; Alfredo Fernández-Landa; Vivian Kvist Johannsen; Miguel Marchamalo; Rasmus Fensholt

doi:10.1038/s41598-017-03469-3

Understanding ‘saturation’ of radar signals over forests

Neha Joshi, Edward Mitchard, Matthew Brolly, Johannes Schumacher, Alfredo Fernández-Landa, Vivian Kvist Johannsen, Miguel Marchamalo, Rasmus Fensholt

University of Brighton

Research output: Contribution to journal › Article › peer-review

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.

Original language	English
Article number	3505
Pages (from-to)	1-11
Journal	Scientific Reports
Volume	7
DOIs	https://doi.org/10.1038/s41598-017-03469-3
Publication status	Published - 14 Jun 2017

Bibliographical note

© The Author(s) 2017. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

Access to Document

10.1038/s41598-017-03469-3Licence: CC BY

art%3A10.1038%2Fs41598-017-03469-3.pdfFinal published version, 5.4 MBLicence: CC BY

Matthew Brolly
- M.Brollybrighton.acuk
- School of Applied Sciences - Principal Lecturer
- Centre for Earth Observation Science
Person: Academic

Cite this

@article{62ff309f1bb1483ca712bd5d36a363d5,

title = "Understanding {\textquoteleft}saturation{\textquoteright} 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 {\textquoteleft}saturation{\textquoteright} 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.",

author = "Neha Joshi and Edward Mitchard and Matthew Brolly and Johannes Schumacher and Alfredo Fern{\'a}ndez-Landa and Johannsen, {Vivian Kvist} and Miguel Marchamalo and Rasmus Fensholt",

note = "{\textcopyright} The Author(s) 2017. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article{\textquoteright}s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article{\textquoteright}s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.",

year = "2017",

month = jun,

day = "14",

doi = "10.1038/s41598-017-03469-3",

language = "English",

volume = "7",

pages = "1--11",

journal = "Scientific Reports",

issn = "2045-2322",

publisher = "Nature Publishing Group UK",

}

TY - JOUR

T1 - Understanding ‘saturation’ of radar signals over forests

AU - Joshi, Neha

AU - Mitchard, Edward

AU - Brolly, Matthew

AU - Schumacher, Johannes

AU - Fernández-Landa, Alfredo

AU - Johannsen, Vivian Kvist

AU - Marchamalo, Miguel

AU - Fensholt, Rasmus

N1 - © The Author(s) 2017. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

PY - 2017/6/14

Y1 - 2017/6/14

N2 - 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.

AB - 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.

U2 - 10.1038/s41598-017-03469-3

DO - 10.1038/s41598-017-03469-3

M3 - Article

VL - 7

SP - 1

EP - 11

JO - Scientific Reports

JF - Scientific Reports

SN - 2045-2322

M1 - 3505

ER -

Understanding ‘saturation’ of radar signals over forests

Abstract

Bibliographical note

Access to Document

Fingerprint

Profiles

Matthew Brolly

Cite this