CO2 stimulates leaf photosynthesis • Is this extra carbon is used to grow more leaves (in the canopy or in the understorey)? 2 CO2 ↑ Forest C uptake ↑ Forest leaf area ↑ Even more uptake?
? • Previous forest FACE experiments have shown a response, sometimes… Duursma 23/10/2017 6 Leaf area index response to eCO2 Leaf area index (control plots)
sensors below canopy in each FACE ring, one above (each ring) • Estimate LAI from transmittance (below canopy / above canopy PAR) Canopy leaf area of a mature evergreen Eucalyptus woodland does not respond to elevated atmospheric [CO2 ] but tracks water availability Remko Duursma, T. Gimeno, M. Boer, K. Crous, M. Tjoelker, D. Ellsworth Global Change Biology, 2016
each ring, 3 times a day • More than 130,000 photos since Nov . 2014 • Analyze images for 'greenness', as G / (R+G+B) • Greenness = Amount of leaves x Colour of leaves
• C4 plants have a CO2 concentrating mechanism, so increasing [CO2 ] has little effect • C3 plants evolved during times when [CO2 ] was high Review of previous FACE data; Ainsworth and Long (2007) ELEVATED CO2 : EXPECTED WINNERS AND LOSERS?
understorey plant community in a Eucalyptus woodland Shun Hasegawa, J. Piñeiro, R. Ochoa-Hueso, A. Haigh, P. Rymer, K. Barnett, S. Power in review ELEVATED CO2 : C4 SPECIES DECLINE, DOMINANT SPECIES WIN
periods of low water availability in a temperate grassy woodland Luke Collins, R. Bradstock, V. Resco de Dios, R. Duursma, S. Velasco, M. Boer in review Custom software analyzes average greenness of the pixels over a 'region of interest' 'Phenocam', a simple camera takes photos every day before sunrise
the result of • 115 thousand photos of the canopy, 35 thousand photos of the understorey • 18 understorey light sensors, 6 above-canopy light sensors, combined 62 million observations of light intensity …and more
woodlands, we need longer timeseries • To inform larger-scale vegetation assessments, comparison with remote sensing methods is underway • Change in species composition over time – is it persistent or transitory? WHAT'S NEXT?
Power, Matthias Boer, Luke Collins, Belinda Medlyn, Mark Tjoelker, Teresa Gimeno, David Ellsworth, Kristine Crous, Paul Rymer, John Drake, and others. Technical Support Gerard Devine, Craig McNamara, Vinod Kumar, Craig Barton, Steve Wohl