| Abstrakt: |
Over the past 100 years, Australia has experienced pronounced changes in rainfall patterns, which in south-western Australia (SWAU) has resulted in both a >50% decrease of runoff since 1975 and effects on vegetation health. Resolving the dynamics of vegetation and climate is a prerequisite for predicting the response of vegetation to future climates and carbon mitigation objectives. With multi-resource vegetation indices (VIs; normalized difference vegetation index and leaf area index) and gridded climate data, this paper examines vegetation dynamics and sensitivity to rainfall change on the Australian continent for the past long drought period (2002-2010). We found that rainfall and VIs declined across 90% and 80% of the whole continent, respectively, compared to the baseline period of 2000-2001. The most dramatic declines in VIs occurred in open shrublands near the center of Australia and in SWAU, coinciding with significant reductions in rainfall and soil moisture. Overall, a strong relationship between water (rainfall and soil moisture) and VIs was detected in places where rainfall declined dramatically (up to 5 mm/year since 1970). For five major vegetation types, croplands showed the highest sensitivity to water change, followed by grasslands and woody savanna. Moderate sensitivity of open shrublands to water change was found, while evergreen broadleaf forests only showed a slight sensitivity to soil moisture change. Although there was no consistent significant relationship between rainfall and VIs of evergreen broadleaf forests, forests in south-eastern Australia, where rainfall had declined since 1997, have become more sensitive to rainfall change than in SWAU. Our results provide evidence that, at this scale of assessment and with interpolated data sets, a lasting reduced rainfall pattern has been a key factor constraining vegetation growth over the Australian continent. [ABSTRACT FROM AUTHOR] |
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