Drought rapidly diminishes the large net CO2 uptake in 2011 over semi-arid Australia

Abstract

Each year, terrestrial ecosystems absorb more than a quarter of the anthropogenic carbon emissions, termed as land carbon sink. An exceptionally large land carbon sink anomaly was recorded in 2011, of which more than half was attributed to Australia. However, the persistence and spatially attribution of this carbon sink remain largely unknown. Here we conducted an observation-based study to characterize the Australian land carbon sink through the novel coupling of satellite retrievals of atmospheric CO2 and photosynthesis and in-situ flux tower measures. We show the 2010–11 carbon sink was primarily ascribed to savannas and grasslands. When all biomes were normalized by rainfall, shrublands however, were most efficient in absorbing carbon. We found the 2010–11 net CO2 uptake was highly transient with rapid dissipation through drought. The size of the 2010–11 carbon sink over Australia (0.97 Pg) was reduced to 0.48 Pg in 2011–12, and was nearly eliminated in 2012–13 (0.08 Pg). We further report evidence of an earlier 2000–01 large net CO2 uptake, demonstrating a repetitive nature of this land carbon sink. Given a significant increasing trend in extreme wet year precipitation over Australia, we suggest that carbon sink episodes will exert greater future impacts on global carbon cycle.

Chlorophyll Fluorescence Better Captures Seasonal and Interannual Gross Primary Productivity Dynamics Across Dryland Ecosystems of Southwestern North America

“…In addition, SIF appears to more accurately capture the relative range of interannual variations in GPP across dryland gradients. Currently, most satellite-based GPP estimates are derived from VI-based proxies (Ma et al, 2016;Sims et al, 2008;Smith et al, 2016). Insights presented here suggest that SIF-based GPP estimates could contribute to improved understanding of drylands and their role in driving interannual variability of the atmospheric CO 2 growth rate (Biederman et al, 2017).…”

Semiarid ecosystem sensitivity to precipitation extremes: weak evidence for vegetation constraints

“…, Ma et al. ). At a more local level, this sensitivity to wet years also has relevance for semiarid ecosystem services such as forage availability, as non‐palatable or exotic forb cover, productivity, and seed dispersion may be facilitated as a result of wet years.…”

“…4), are likely to drive this semiarid ecosystem to a considerable carbon sink during wet years. This dynamic indicates that responses to wet years are an integral component of carbon cycle dynamics within semiarid ecosystems (Haverd et al 2016), and has implications to global scales as the sensitivity of semiarid regions to precipitation continues to drive variability in the land CO 2 sink (Poulter et al 2014, Ahlstrom et al 2015, Ma et al 2016. At a more local level, this sensitivity to wet years also has relevance for semiarid ecosystem services such as forage availability, as non-palatable or exotic forb cover, productivity, and seed dispersion may be facilitated as a result of wet years.…”

Recovery of Ecosystem Carbon and Energy Fluxes From the 2003 Drought in Europe and the 2012 Drought in the United States

“…In recent years, extreme droughts have struck Europe (Ciais et al, 2005), America (Wolf et al, 2016), Australia (Ma et al, 2016), China (Yuan et al, 2016), the Amazon rain forest region (Lewis et al, 2011;Phillips et al, 2009), etc. and significantly impacted the dynamics of ecosystem functions.…”