Improved annual forest cover maps in Oklahoma from analyses of PALSAR-2, Landsat, and LiDAR data sets during 2015–2021

Abstract

Accurate forest cover maps are the basis for estimating forest biomass and are crucial for climate regulation and biodiversity conservation, especially in sub-humid and semi-arid regions such as Oklahoma, USA. To date, there is very limited data and knowledge of the spatial pattern and temporal dynamics of forest cover in Oklahoma, and current forest cover maps have large uncertainties. In this study, multi-sensor datasets, including the Phased Arrayed L-band Synthetic Aperture Radar (PALSAR-2), Landsat, and spaceborne Light Detection and Ranging (LiDAR), were combined to generate annual forest cover maps for the years 2015 to 2021. Specifically, both PALSAR-derived HV, HH-HV, and HH/HV and Landsat-derived Normalized Difference Vegetation Index (NDVI) were used together to generate annual maps of forest cover and three forest types (evergreen, deciduous, and mixed forest) at 30-m spatial resolution for each year. The canopy height and canopy coverage samples from the Global Ecosystem Dynamics Investigation (GEDI) and the Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) were used to assess forest cover maps. We also compared the spatial distribution and forested area of several forest products. Our results show that using the forest definition (canopy height > 5 m, canopy coverage > 10% over an area of 0.5 ha) of the Food and Agriculture Organization of the United Nations (FAO), the accuracy of resultant PALSAR/Landsat forest cover map for 2019 were 77.4% (GEDI) and 95.6% (ICESat-2). The estimated forested area (51,916 km²) was moderately higher (7.2%) than the forested area from the USDA Forest Inventory and Analysis (FIA) statistics dataset (48,202 km²) in 2017. Between 2016 and 2020, Oklahoma’s forested area increased slightly by 1.9%. The PALSAR/Landsat forest maps are more accurate in western Oklahoma compared to other satellite-based forest products. The resultant annual maps of forest cover and three different forest types over Oklahoma can be used to support statewide forest management and conservation.

Graphical abstract

Keywords

forest cover / evergreen forest / knowledge-based / phenology-based / land cover change

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Acknowledgments

This study was supported in part by research grants from the US National Science Foundation (OIA-1946093, OIA-1920946).

Electronic Supplementary

Material is available in the online version of this article at http://dx.doi.org/10.1007/s11707-025-1151-4 and is accessible for authorized users.

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