Modeling Surface Energy Fluxes over a Dehesa (Oak Savanna) Ecosystem Using a Thermal Based Two Source Energy Balance Model (TSEB) II—Integration of Remote Sensing Medium and Low Spatial Resolution Satellite Images

Ana Andreu,Arnaud Carrara,Maria González-Dugo,William Kustas,Maria Polo

doi:10.3390/rs10040558

Abstract

Dehesas are highly valuable agro-forestry ecosystems, widely distributed over Mediterranean-type climate areas, which play a key role in rural development, basing their productivity on a sustainable use of multiple resources (crops, livestock, wildlife, etc.). The information derived from remote sensing based models addressing ecosystem water consumption, at different scales, can be used by institutions and private landowners to support management decisions. In this study, the Two-Source Energy Balance (TSEB) model is analyzed over two Spanish dehesa areas integrating multiple satellites (MODIS and Landsat) for estimating water use (ET), vegetation ground cover, leaf area and phenology. Instantaneous latent heat (LE) values are derived on a regional scale and compared with eddy covariance tower (ECT) measurements, yielding accurate results (RMSDMODIS Las Majadas 44 Wm−2, Santa Clotilde RMSDMODIS 47 Wm−2 and RMSDLandsat 64 Wm−2). Daily ET(mm) is estimated using daily return interval of MODIS for both study sites and compared with the flux measurements of the ECTs, with RMSD of 1 mm day−1 over Las Majadas and 0.99 mm day−1 over Santa Clotilde. Distributed ET over Andalusian dehesa (15% of the region) is successfully mapped using MODIS images, as an approach to monitor the ecosystem status and the vegetation water stress on a regular basis.

Highlights

Dehesas, as evergreen oak savannas are known over Spain, are highly valuable agro-forestry ecosystems, widely distributed over Mediterranean-type climate areas (e.g., Portugal, Greece, California and South Africa)
The Two-Source Energy Balance (TSEB) model is analyzed over two Spanish dehesa areas integrating multiple satellites (MODIS and Landsat) for estimating water use (ET), vegetation ground cover, leaf area and phenology
Instantaneous latent heat (LE) values are derived on a regional scale and compared with eddy covariance tower (ECT) measurements, yielding accurate results (RMSDMODIS Las Majadas 44 Wm−2, Santa Clotilde RMSDMODIS 47 Wm−2 and RMSDLandsat 64 Wm−2)

Summary

Introduction

As evergreen oak savannas are known over Spain, are highly valuable agro-forestry ecosystems, widely distributed over Mediterranean-type climate areas (e.g., Portugal, Greece, California and South Africa). They cover about 2.5 million hectares in Spain—80% of this surface in Andalusia and Extremadura regions [1]—and play a key role in the rural development of the region, basing their productivity on a sustainable use of multiple resources (crops, livestock, wildlife and natural services). Modeling and monitoring water use, evapotranspiration (ET), and water stress, ratio of actual to potential ET, at large scales is considered key in assessing changes in dehesa ecosystem functioning, and it is possible through the integration of Earth Observation data into process-based models

Methods

Results

Conclusion