Phenological shifts in Australian grasslands observed using satellite data

The grass and pasture lands in eastern Australia are essential contributors to the productivity and biodiversity of Australia as they support the Agricultural production of wool, lamb, and beef. This highly productive eastern Australian belt consists of modified and fragmented landscapes with dryland management uses, heterogenous patches, and the prevalence of invasive species. Remote sensing provides a means for monitoring these grass / pasture over a large area. In this study, phenology of these grasslands was analyzed across a precipitation and latitudinal temperature gradient encompassing warm season (C4) and cool season (C3) grass functional types. Using vegetation time series data from MODerate-resolution Imaging Spectroradiometer (MODIS) global vegetation index product, we retrieved phenological metrics of these grasslands and tested the hypothesis of shifting abundance and timing of C3-C4 grasslands associated with grass productivity changes due to changes in seasonal rainfall patterns. Our results show that in these water-limited dryland environments in eastern Australia, phenology is largely driven by water availability. In addition to temporal shifts in grass growing seasons, we found shifts in the abundance of C3 and C4 grasslands across 15 years from 2003 to 2017. Our study demonstrates the potential of the MODIS data for providing spatially-detailed mapping of grassland composition, and our findings reveal the significant role of rainfall in regulating the phenology of these grasslands. These results demonstrate the impacts of rainfall patterns on Southern Hemisphere grassland ecosystems, and provide valuable information for the adaptation of southeast Australia's agricultural and fire management practices to changing climatic conditions.