What drives carbon exchange between a temperate sclerophyll forest - - PowerPoint PPT Presentation

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What drives carbon exchange between a temperate sclerophyll forest - - PowerPoint PPT Presentation

Oct 22, 2023 129 likes •389 views

Annual net exchange of carbon What drives carbon exchange between a temperate sclerophyll forest and the atmosphere on time scales from hours to multiple years? Eva van Gorsel 1 , Heather Keith 2 , Helen Cleugh 1 , Vanessa Haverd 1 and Ray

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Eva van Gorsel1, Heather Keith2, Helen Cleugh1, Vanessa Haverd1 and Ray Leuning1

(1) CSIRO Marine and Atmospheric Research, Canberra, Australia (2) The Fenner School of Environment and Society, ANU, Canberra, Australia

What drives carbon exchange between a temperate sclerophyll forest and the atmosphere on time scales from hours to multiple years?

Annual net exchange of carbon

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  • CSIRO. TEMPORAL VARIABILITY IN CO2 EXCHANGE

Variability of NEE, FLUXNET

From: D. Baldocchi, 2008, Aust. J. of Botany Tumbarumba min: -963 g C m-2 yr-1 Carbon uptake max: 145 g C m-2 yr-1 Carbon efflux

Published measurements of annual net ecosystem exchange of CO2 (NEE) in a range of global ecosystems

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  • CSIRO. TEMPORAL VARIABILITY IN CO2 EXCHANGE

Tumbarumba Site: Part of OzFlux

OzFlux

Tumbarumba Flux Tower in SE highlands of NSW Bago State Forest

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Tumbarumba Site: Topography

  • CSIRO. TEMPORAL VARIABILITY IN CO2 EXCHANGE
  • 40 m tall Eucalypt forest with a Leaf Area Index ~ 2.4
  • Alpine Ash E. Delegatensis
  • Mountain White Gum E. dalrympleana
  • Forest cover and species homogenous within radius > 5 km
  • Shallow basin sloping towards North

Photographs : Dale Hughes

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  • Direct measure of CO2 and water

vapour fluxes between the canopy and the atmosphere

–Water (λE, ET) and CO2 (NEE)

  • Energy fluxes

–Radiation (Q) and heat (H, G)

  • Above canopy, spatially-averaged
  • ver an area ~ 1 – 5 km
  • Continuous – hourly to multi-annual

H

Measuring ecosystem water and carbon fluxes

NEE

ET

Q G

ET Q

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  • CSIRO. TEMPORAL VARIABILITY IN CO2 EXCHANGE

Climate at Bago State Forest (AWAP data)

1380 mm 22.7 °C

  • 1.09 °C
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Temperature / precipitation measured at site

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Ecosystem carbon fluxes vary in response to these meteorological drivers ….

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  • CSIRO. TEMPORAL VARIABILITY IN CO2 EXCHANGE

.. and also disturbance

  • J. Verbesselt et al., 2010, Forest Ecol. Manag.

Leaves damaged by insect attack (psyllids) in summer 2002 – 03; severely damaged leaves shed in autumn 2003 2002 2006

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Modelling net ecosystem exchange of CO2 (NEE)

Hyperbolic light-response curve (Michaelis-Menten)

  • canopy light utilization efficiency (μmol C J-1)

b maximum CO2 uptake rate of canopy at light saturation (μ mol C m-2 s-1)

  • terrestrial ecosystem respiration (μmol C m-2 s-1)
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include temperature dependence of respiration include dependence on vapour pressure deficit (VPD) 30 day moving window

Modelling net ecosystem exchange of CO2 (NEE)

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  • CSIRO. TEMPORAL VARIABILITY IN CO2 EXCHANGE

Model performance

Captures diurnal variability …

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  • CSIRO. TEMPORAL VARIABILITY IN CO2 EXCHANGE

Model performance

This means that we can use this model to quantify the effect

  • f each of the meteorological drivers on the components of

the carbon cycle (GPP, RE and NEE)

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  • CSIRO. TEMPORAL VARIABILITY IN CO2 EXCHANGE

Ecosystem assimilation (GPP) 2001-2009

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  • CSIRO. TEMPORAL VARIABILITY IN CO2 EXCHANGE

Ecosystem assimilation (GPP) 2001-2009

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Ecosystem respiration (RE) 2001-2009

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NEE, GPP and RE

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Timescales of variability: Drivers and fluxes [2002-2009]

shortwave incoming radiation soil temperature vapour pressure deficit soil water content leaf area index

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shortwave incoming radiation soil temperature vapour pressure deficit soil water content leaf area index

Timescales of variability: Drivers and fluxes [2002-2009]

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  • CSIRO. TEMPORAL VARIABILITY IN CO2 EXCHANGE

Conclusions / Summary (1)

Highly dynamic forest ecosystem where the CO2 fluxes: Respond mainly to the meteorological drivers:

  • radiation and soil temperature [hourly]
  • radiation and SWC [seasonal]
  • VPD, SWC and radiation [annual]
  • LAI and SWC [multi annual]

Are subject to stress caused by meteorological drivers

  • Drought (low soil moisture → RE / high VPD → GPP)
  • Disturbance – insect predation that is linked to antecedent

weather conditions → GPP

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  • CSIRO. TEMPORAL VARIABILITY IN CO2 EXCHANGE

Conclusions / Summary (2)

The response to these combined stressors resulted in:

  • reduced leaf area
  • reduced stomatal conductance and photosynthetic capacity
  • reduced assimilation
  • reduced biomass increment
  • increased mortality

Effect of disturbance (insects) on ecosystem assimilation is greater than on ecosystem respiration Carbon sink turned to a source for several months

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CSIRO Marine and Atmospheric Research Helen Cleugh Email: helen.cleugh@csiro.au Web: www.cmar.csiro.au

Contact Us Phone: 1300 363 400 or +61 3 9545 2176 Email: enquiries@csiro.au Web: www.csiro.au

Thank you

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… as does tree mortality

2002 – 2005 drought years 1998 – 2001 average rainfall

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… and biomass increment

average rainfall drought years