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Satellite Determination of Peatland Water Table Temporal Dynamics by Localizing Representative Pixels of A SWIR-Based Moisture Index

Burdun, Iuliia and Bechtold, Michel and Sagris, Valentina and Lohila, Annalea and Humphreys, Elyn and Desai, Ankur R. and Nilsson, Mats and De Lannoy, Gabrielle and Mander, Ulo (2020). Satellite Determination of Peatland Water Table Temporal Dynamics by Localizing Representative Pixels of A SWIR-Based Moisture Index. Remote Sensing. 12 , 2936
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Abstract

The OPtical TRApezoid Model (OPTRAM) is a physically-based approach for remote soil moisture estimation. OPTRAM is based on the response of short-wave infrared (SWIR) reflectance to vegetation water status, which in turn responds to changes of root-zone soil moisture. In peatlands, the latter is tightly coupled to water table depth (WTD). Therefore, in theory, the OPTRAM index might be a useful tool to monitor WTD dynamics in peatlands, although the sensitivity of OPTRAM index to WTD changes will likely depend on vegetation cover and related rooting depth. In this study, we aim at identifying those locations (further called 'best pixels') where the OPTRAM index is most representative of overall peatland WTD dynamics. In peatlands, the high saturated hydraulic conductivity of the upper layer largely synchronizes the temporal WTD fluctuations over several kilometers, i.e., even though the mean and amplitude of the WTD dynamics may vary in space. Therefore, it can be assumed that the WTD time series, either measured at a single location or simulated for a grid cell with the PEATland-specific adaptation of the NASA Catchment Land Surface Model (PEATCLSM), are representative of the overall peatland WTD dynamics. We took advantage of this concept to identify the 'best pixel' of all spatially distributed OPTRAM pixels within a peatland, as that pixel with the highest time series Pearson correlation (R) with WTD data accounting for temporal autocorrelation. The OPTRAM index was calculated based on various remotely sensed images, namely, Landsat, MODIS, and aggregated Landsat images at MODIS resolution for five northern peatlands with long-term WTD records, including both bogs and fens. The 'best pixels' were dominantly covered with mosses and graminoids with little or no shrub or trees. However, the performance of OPTRAM highly depended on the spatial resolution of the remotely sensed data. The Landsat-based OPTRAM index yielded the highest R values (mean of 0.7 across the 'best pixels' in five peatlands). Our study further indicates that, in the absence of historical in situ data, PEATCLSM can be used as an alternative to localize 'best pixels'. This finding enables the future applicability of OPTRAM to monitor WTD changes in peatlands on a global scale.

Authors/Creators:Burdun, Iuliia and Bechtold, Michel and Sagris, Valentina and Lohila, Annalea and Humphreys, Elyn and Desai, Ankur R. and Nilsson, Mats and De Lannoy, Gabrielle and Mander, Ulo
Title:Satellite Determination of Peatland Water Table Temporal Dynamics by Localizing Representative Pixels of A SWIR-Based Moisture Index
Series Name/Journal:Remote Sensing
Year of publishing :2020
Volume:12
Article number:2936
Number of Pages:21
Publisher:MDPI
Language:English
Publication Type:Journal article
Article category:Scientific peer reviewed
Version:Published version
Copyright:Creative Commons: Attribution 4.0
Full Text Status:Public
Subjects:(A) Swedish standard research categories 2011 > 2 Engineering and Technology > 207 Environmental Engineering > Remote Sensing
Keywords:Landsat, MODIS, bogs, fens, sphagnum, soil moisture, wetland, shortwave infrared transformed reflectance
URN:NBN:urn:nbn:se:slu:epsilon-p-109010
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-p-109010
Additional ID:
Type of IDID
DOI10.3390/rs12182936
Web of Science (WoS)000581848600001
ID Code:19100
Faculty:S - Faculty of Forest Sciences
Department:(S) > Dept. of Forest Ecology and Management
Deposited By: SLUpub Connector
Deposited On:03 Dec 2020 12:43
Metadata Last Modified:15 Jan 2021 19:19

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