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Article

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

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Institute of Ecology & Earth Sciences, Department of Geography, University of Tartu, 51014 Tartu, Estonia
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Department of Earth and Environmental Sciences, KU Leuven, 3001 Heverlee, Belgium
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Department of Computer Science, KU Leuven, 3001 Heverlee, Belgium
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Finnish Meteorological Institute, Climate System Research, FI-00101 Helsinki, Finland
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Institute for Atmospheric and Earth System Research/Physics, Faculty of Science, University of Helsinki, FI-00014 Helsinki, Finland
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Department of Geography and Environmental Studies, Carleton University, Ottawa, ON K1S 5B6, Canada
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Department of Atmospheric and Oceanic Sciences, University of Wisconsin-Madison, Madison, WI 53706, USA
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Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, 90183 Umeå, Sweden
*
Author to whom correspondence should be addressed.
Remote Sens. 2020, 12(18), 2936; https://doi.org/10.3390/rs12182936
Received: 24 July 2020 / Revised: 29 August 2020 / Accepted: 8 September 2020 / Published: 10 September 2020
(This article belongs to the Section Environmental Remote Sensing)
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. View Full-Text
Keywords: Landsat; MODIS; bogs; fens; sphagnum; soil moisture; wetland; shortwave infrared transformed reflectance Landsat; MODIS; bogs; fens; sphagnum; soil moisture; wetland; shortwave infrared transformed reflectance
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MDPI and ACS Style

Burdun, I.; Bechtold, M.; Sagris, V.; Lohila, A.; Humphreys, E.; Desai, A.R.; Nilsson, M.B.; De Lannoy, G.; Mander, Ü. Satellite Determination of Peatland Water Table Temporal Dynamics by Localizing Representative Pixels of A SWIR-Based Moisture Index. Remote Sens. 2020, 12, 2936. https://doi.org/10.3390/rs12182936

AMA Style

Burdun I, Bechtold M, Sagris V, Lohila A, Humphreys E, Desai AR, Nilsson MB, De Lannoy G, Mander Ü. Satellite Determination of Peatland Water Table Temporal Dynamics by Localizing Representative Pixels of A SWIR-Based Moisture Index. Remote Sensing. 2020; 12(18):2936. https://doi.org/10.3390/rs12182936

Chicago/Turabian Style

Burdun, Iuliia, Michel Bechtold, Valentina Sagris, Annalea Lohila, Elyn Humphreys, Ankur R. Desai, Mats B. Nilsson, Gabrielle De Lannoy, and Ülo Mander. 2020. "Satellite Determination of Peatland Water Table Temporal Dynamics by Localizing Representative Pixels of A SWIR-Based Moisture Index" Remote Sensing 12, no. 18: 2936. https://doi.org/10.3390/rs12182936

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