Details

Autor(en) / Beteiligte

• Koupaei‐Abyazani, Nikaan
• Burdun, Iuliia
• Desai, Ankur R.
• Hergoualc'h, Kristell
• Hirano, Takashi
• Melling, Lulie
• Swails, Erin
• Ing Tang, Angela Che
• Wong, Guan Xhuan

Titel

Tropical Peatland Water Table Estimations From Space

Ist Teil von

• Journal of geophysical research. Biogeosciences, 2024-06, Vol.129 (6), p.n/a

Ort / Verlag

Washington: Blackwell Publishing Ltd

Erscheinungsjahr

2024

Quelle

Wiley-Blackwell Journals

Beschreibungen/Notizen

• Tropical peatlands store copious amounts of carbon (C) and play a critical role in the global C cycle. However, this C store is vulnerable to natural and anthropogenic disturbances, leading these ecosystems to become weaker C sinks or even net C sources. Variabilities in water table (WT) greatly influence the magnitude of greenhouse gas flux in these biomes. Despite its importance in C cycling, observations of the spatiotemporal dynamics of tropical peatland WT are limited in spatial extent and length. Here, we use in situ WT measurements from tropical peatlands in Indonesia, Malaysia, and Peru to evaluate the satellite‐based Optical Trapezoid Model (OPTRAM). The model uses the pixel distribution in the shortwave infrared transformed reflectance and normalized difference vegetation index (NDVI) space to calculate indices that are then compared against in situ WT data. 30‐m resolution Landsat 7 and Landsat 8 images were utilized for model parameterization. We found OPTRAM to best capture tropical peatland WT dynamics in minimally forested and non‐forested areas (low to intermediate NDVI) (0.7 < R < 1) using the “best pixel” approach (the pixel with the highest Pearson‐R correlation value). In areas with relatively higher NDVI, OPTRAM index did not correlate with WT (average R of −0.04 to 0.24), likely due to trees being less sensitive to WT fluctuations. OPTRAM shows potential for reliably estimating tropical peatland WT without the need for direct measurements, which is challenging due to site remoteness and harsh conditions. Plain Language Summary Tropical peatlands store copious amounts of carbon in their soil and biomass. The position of the water table (WT) relative to the soil surface plays a large role in how much greenhouse gases (GHGs) (i.e., carbon dioxide, methane, and nitrous oxide) is emitted or taken up and may also give insight into areas most vulnerable to fire. Therefore, estimating tropical peatland WT fluctuations over space and time is essential for understanding the global carbon and GHG budgets. Due to harsh environmental conditions and site remoteness, direct measurements of tropical peatland WT are limited in spatial extent and length. As a result, other methods must be developed to estimate the spatiotemporal variability of this parameter. Through manipulation of satellite surface reflectance, we demonstrate the feasibility of estimating fluctuations in tropical peatland WT from space. This method is tested on sites spanning Peru, Indonesia, and Malaysia. We find that WT fluctuations are accurately quantified over areas that are minimally forested or non‐forested. Our findings provide a pathway to map tropical peatland WT from space leading to improved understanding of WT‐dependent processes such as GHG emissions and fire risk, both of which contribute greatly to global climate change. Key Points OPTRAM is capable of accurately capturing the temporal variability of tropical peatland water table OPTRAM performs optimally over minimally forested and non‐forested areas