@article{22569,
  abstract     = {Despite their size and contribution to the global carbon cycle, we have limited understanding of tropical savannas and their current trajectory with climate change and anthropogenic pressures. Here we examined interannual variability and externally forced long-term changes in carbon and water exchange from a high rainfall savanna site in the seasonal tropics of north Australia. We used an 18-year flux data time series (2001–2019) to detect trends and drivers of fluxes of carbon and water. Significant positive trends in gross primary productivity (GPP, 15.4 g C m2 year−2), ecosystem respiration (Reco, 8.0 g C m2 year−2), net ecosystem productivity (NEE, 7.4 g C m2 year−2) and ecosystem water use efficiency (WUE, 0.0077 g C kg H2O−1 year−1) were computed. There was a weaker, non-significant trend in latent energy exchange (LE, 0.34 W m−2 year−1). Rainfall from a nearby site increased statistically over a 45-year period during the observation period. To examine the dominant drivers of changes in GPP and WUE, we used a random forest approach and a terrestrial biosphere model to conduct an attribution experiment. Radiant energy was the dominant driver of wet season fluxes, whereas soil water content dominated dry season fluxes. The model attribution suggested that [CO2], precipitation and Tair accounting for 90% of the modelled trend in GPP and WUE. Positive trends in fluxes were largest in the dry season implying tree components were a larger contributor than the grassy understorey. Fluxes and environmental drivers were not significant during the wet season, the period when grasses are active. The site is potentially still recovering from a cyclone 45 years ago and regrowth from this event may also be contributing to the observed trends in sequestration, highlighting the need to understand fluxes and their drivers from sub-diurnal to decadal scales.},
  author       = {Hutley, Lindsay B. and Beringer, Jason and Fatichi, Simone and Schymanski, Stanislaus J. and Northwood, Matthew},
  issn         = {1365-2486},
  journal      = {Global Change Biology},
  keywords     = {CO2 fertilization, Ecosystem model, Eddy covariance, Howard Springs, Water use efficiency},
  number       = {7},
  pages        = {2360--2380},
  publisher    = {Wiley},
  title        = {{Gross primary productivity and water use efficiency are increasing in a high rainfall tropical savanna}},
  doi          = {10.1111/gcb.16012},
  volume       = {28},
  year         = {2022},
}

@article{22570,
  abstract     = {Atmospheric carbon dioxide concentration ([CO 2 ]) is increasing, which increases leaf-scalephotosynthesis and intrinsic water-use efficiency. These direct responses have the potential toincrease plant growth, vegetation biomass, and soil organic matter; transferring carbon from theatmosphere into terrestrial ecosystems (a carbon sink). A substantial global terrestrial carbon sinkwould slow the rate of [CO 2] increase and thus climate change. However, ecosystem CO2responses are complex or confounded by concurrent changes in multiple agents of global changeand evidence for a [CO 2]-driven terrestrial carbon sink can appear contradictory. Here wesynthesize theory and broad, multidisciplinary evidence for the effects of increasing [CO 2](iCO 2) on the global terrestrial carbon sink. Evidence suggests a substantial increase in globalphotosynthesis since pre-industrial times. Established theory, supported by experiments,indicates that iCO 2 is likely responsible for about half of the increase. Global carbon budgeting,atmospheric data, and forest inventories indicate a historical carbon sink, and these apparentiCO 2 responses are high in comparison to experiments and predictions from theory. Plantmortality and soil carbon iCO 2 responses are highly uncertain. In conclusion, a range of evidencesupports a positive terrestrial carbon sink in response to iCO2 , albeit with uncertain magnitudeand strong suggestion of a role for additional agents of global change.},
  author       = {Walker, Anthony P. and De Kauwe, Martin G. and Bastos, Ana and Belmecheri, Soumaya and Georgiou, Katerina and Keeling, Ralph F. and McMahon, Sean M. and Medlyn, Belinda E. and Moore, David J. P. and Norby, Richard J. and Zaehle, Sönke and Anderson‐Teixeira, Kristina J. and Battipaglia, Giovanna and Brienen, Roel J. W. and Cabugao, Kristine G. and Cailleret, Maxime and Campbell, Elliott and Canadell, Josep G. and Ciais, Philippe and Craig, Matthew E. and Ellsworth, David S. and Farquhar, Graham D. and Fatichi, Simone and Fisher, Joshua B. and Frank, David C. and Graven, Heather and Gu, Lianhong and Haverd, Vanessa and Heilman, Kelly and Heimann, Martin and Hungate, Bruce A. and Iversen, Colleen M. and Joos, Fortunat and Jiang, Mingkai and Keenan, Trevor F. and Knauer, Jürgen and Körner, Christian and Leshyk, Victor O. and Leuzinger, Sebastian and Liu, Yao and MacBean, Natasha and Malhi, Yadvinder and McVicar, Tim R. and Penuelas, Josep and Pongratz, Julia and Powell, A. Shafer and Riutta, Terhi and Sabot, Manon E. B. and Schleucher, Juergen and Sitch, Stephen and Smith, William K. and Sulman, Benjamin and Taylor, Benton and Terrer, César and Torn, Margaret S. and Treseder, Kathleen K. and Trugman, Anna T. and Trumbore, Susan E. and van Mantgem, Phillip J. and Voelker, Steve L. and Whelan, Mary E. and Zuidema, Pieter A.},
  issn         = {1469-8137},
  journal      = {New Phytologist},
  keywords     = {Beta factor, Carbon dioxide, CO2 fertilization, CO2-fertilization hypothesis, Free-air CO2 enrichment (FACE), Global carbon cycle, Land–atmosphere feedback, Terrestrial ecosystems},
  number       = {5},
  pages        = {2413--2445},
  publisher    = {Wiley},
  title        = {{Integrating the evidence for a terrestrial carbon sink caused by increasing atmospheric CO2}},
  doi          = {10.1111/nph.16866},
  volume       = {229},
  year         = {2021},
}