Interpreting the stable isotope composition of tree-ring cellulose Lisa Wingate & Jérôme Ogée INRA, EPHYSE, Bordeaux, France The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012

Photosynthetic and evaporative processes govern the stable isotope composition of cellulose air cellulose pool assimilates =13C/12C The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 2

Principles of photosynthetic carbon discrimination ‘light’ (12CO2) 4 10 20 30 a ~4.4‰ Discrimination [13DA, ‰ ] b3 Calvin cycle ~27‰ 0.2 0.4 0.6 0.8 1.0 sugars Ci /Ca Francey & Farquhar, 1982 Farquhar, O’Leary & Berry, 1982 wood The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 3

Photosynthetic and evaporative processes govern the stable isotope composition of cellulose air cellulose pool leafwater =18O/16O soil The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 4

Principles of leaf water enrichment ‘light’ water (H216O) ‘heavy’ water (H218O) Craig & Gordon, 1965 Dongmann et al., 1974 Wingate et al., 2010 The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 5

Photosynthetic and evaporative processes govern the stable isotope composition of cellulose air cellulose pool leafwater assimilates soil The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 6

Seasonal variations in cellulose stable isotope composition linked to productivity and climate Maritime pine, Les Landes The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 7

Seasonal variations in cellulose stable isotope composition linked to productivity and climate drought years Maritime pine, Les Landes Narrow rings generally associated with sharp peaks in d13C during the growing season. They also often start the growing season from a relatively enriched value. The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 8

thick rings no d13C spikes Seasonal variations in cellulose stable isotope composition linked to productivity and climate drought years Maritime pine, Les Landes Relatively wet years tend to have little variation in d13C over the season and appear flat compared to drought years. The d18O signal tends to be less dramatic but nonetheless can provide clues for instance enriched values tend to indicate relatively high levels of transpiration and evaporative enrichment, for example in 2002 there is a peak at the start of the season prior to the drought and 2005 there also seems to be a strong transpiration rate. productive years thick rings no d13C spikes wet years The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 9

Ecosystem variations in stable isotope composition Varriö, Finland Pinus sylvestris 67’46’N 29’34’E Hyttiälä, Finland Pinus sylvestris 61’50’N 24’17’E Tharandt, Germany Picea abies 50’58’N 13’34’E Les Landes, France Pinus pinaster 44’43’N 00’46’E Relatively wet years tend to have little variation in d13C over the season and appear flat compared to drought years. The d18O signal tends to be less dramatic but nonetheless can provide clues for instance enriched values tend to indicate relatively high levels of transpiration and evaporative enrichment, for example in 2002 there is a peak at the start of the season prior to the drought and 2005 there also seems to be a strong transpiration rate. Yatir, Israel Pinus halepensis 31’20’N 35’03’E The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 10

Ecosystem variations in stable isotope composition Varriö, Finland Pinus sylvestris 67’46’N 29’34’E Hyttiälä, Finland Pinus sylvestris 61’50’N 24’17’E Tharandt, Germany Picea abies 50’58’N 13’34’E Les Landes, France Pinus pinaster 44’43’N 00’46’E Relatively wet years tend to have little variation in d13C over the season and appear flat compared to drought years. The d18O signal tends to be less dramatic but nonetheless can provide clues for instance enriched values tend to indicate relatively high levels of transpiration and evaporative enrichment, for example in 2002 there is a peak at the start of the season prior to the drought and 2005 there also seems to be a strong transpiration rate. Yatir, Israel Pinus halepensis 31’20’N 35’03’E The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 11

Photosynthetic and evaporative processes can be modelled from theory convection/ evaporation photosynthesis/respiration light and rain interception turbulent transport heat/moisture storage MuSICA Ogée et al., 2003 The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 12

Photosynthetic and evaporative processes can be modelled from theory Maritime pine, Les Landes Soil water content [kg m-2] Net CO2 flux [gC m-2d-1] Ecosystem Latent heat flux Ecosystem [MJ m-2d-1] 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 13

Isotopic fractionations can also be modelled from theory Etransp, lw Etransp, sw MuSICA Ogée et al., 2009 The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 14

…from fluxes to cellulose The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 15

…from fluxes to cellulose Sugar transfer The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 16

…from fluxes to cellulose Sugar transfer Cellulose synthesis 17

Most of the earlywood formed when minimum leaf water potentials are around -1MPa. The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 18

Cellulose signals can be modelled from theory Maritime pine, Les Landes The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 19

Most of the earlywood formed when minimum leaf water potentials are around -1MPa. The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 20

Reconstructing period of cellulose deposition The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 21

Linking isotope signals to plant water potential Maritime pine, Les Landes latewood Most of the earlywood formed when minimum leaf water potentials are around -1MPa. earlywood The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 22

Perspectives Future developments, investigations and novel applications - Use model to identify thresholds for wood growth Use model to identify triggers for latewood formation Use model to predict wood density variations Use model to reconstruct growing season lengths Use model and cellulose to reconstruct plant function Use cellulose archives to improve SVAT models The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012

Seasonal variations in cellulose stable isotope composition closely linked to wood density Maritime pine, Les Landes The significance of xylem hydraulic plasticity for reconstructing past environments: Kippel, May 15th – 17th 2012 24