Spatio-Temporal Dynamics of Water Use Efficiency of Forest Ecosystem Using Time Series Satellite Data and Flux Measurements

Abstract:

Water use efficiency (WUE) of a forest ecosystem portrays the coupling of carbon and water-energy nexus. As the forest ecosystem is a dynamic framework, the interactions between the carbon and the water cycle at an awfully huge scale can determine the intra-annual as well as inter annual inconstancy of WUE and the carbon budget of terrestrial ecosystem. The WUE of distinctive vegetation types of totally different regions moves forward our understanding of the nature of its reaction to climate change. Two different forest environments; a moist deciduous forest at Barkot Flux Research Site and the other, a dry deciduous forest at Haldwani Flux Research Sites with eddy covariance system were chosen for continuous observation of C, water and energy fluxes for 2016 to 2018. The spatio-temporal variability of WUE is examined using eddy covariance measurements and cloud-free Landsat OLI images along with different C and water flux components of the years 2016 to 2018. Variation in WUE was found at monthly and annual scale over the both sites. Annual average WUE was 2.47 gC kg-¹H₂O year^-1 and 0.59 gC kg-¹H₂O year^-1 for Barkot and Haldwani flux sites respectively. The highest WUE was noticed at barkot in 2017 and it amounts to 8.18 gC kg-¹H₂O month^-1. Whereas the lowest observed WUE was 0.039 gC kg-¹H₂O month^-1 in 2018 at Haldwani. The predicted WUE also shows good corelation to the observed data with R² value 0.68.The two regional forest ecosystems showed an asynchronous response of GPP and ET to climatic variables which determined the coupling and decoupling between C and water cycles. Variations in WUE indicated the difference in the coupling between C and water cycle.