Large-scale vegetation responses to terrestrial moisture storage changes

Robert L. Andrew,Okke Batelaan,Huade Guan

doi:10.5194/hess-21-4469-2017

Abstract

Abstract. The normalised difference vegetation index (NDVI) is a useful tool for studying vegetation activity and ecosystem performance at a large spatial scale. In this study we use the Gravity Recovery and Climate Experiment (GRACE) total water storage (TWS) estimates to examine temporal variability of the NDVI across Australia. We aim to demonstrate a new method that reveals the moisture dependence of vegetation cover at different temporal resolutions. Time series of monthly GRACE TWS anomalies are decomposed into different temporal frequencies using a discrete wavelet transform and analysed against time series of the NDVI anomalies in a stepwise regression. The results show that combinations of different frequencies of decomposed GRACE TWS data explain NDVI temporal variations better than raw GRACE TWS alone. Generally, the NDVI appears to be more sensitive to interannual changes in water storage than shorter changes, though grassland-dominated areas are sensitive to higher-frequencies of water-storage changes. Different types of vegetation, defined by areas of land use type, show distinct differences in how they respond to the changes in water storage, which is generally consistent with our physical understanding. This unique method provides useful insight into how the NDVI is affected by changes in water storage at different temporal scales across land use types.

Highlights

In many parts of the world, such as Australia, water storage is the dominant limiting factor in vegetation growth (Donohue et al, 2008; Nemani et al, 2003)
In this study we aimed to increase the understanding of largescale ecosystem responses to water storage by investigating the links between Gravity Recovery and Climate Experiment (GRACE) total water storage (TWS)∗ and normalised difference vegetation index (NDVI)∗ using decomposed TWS∗ data
Combinations of decomposed GRACE TWS∗ data show an improved relationship with NDVI∗ compared to using raw GRACE TWS∗ data alone

Summary

Introduction

In many parts of the world, such as Australia, water storage is the dominant limiting factor in vegetation growth (Donohue et al, 2008; Nemani et al, 2003). Precipitation and soil moisture have been used as defining variables (Chen et al, 2014; Huxman, 2004; Méndez-Barroso et al, 2009; Wang et al, 2007). Both of these have shown generally meaningful correlations with ecosystem performance (by various measures such as the normalised difference vegetation index, NDVI, and above-ground net primary production). In situ soil moisture data are generally limited and spatially

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Discussion

Conclusion