Elevated [CO2] and forest vegetation: more a water issue than a carbon issue?
Joseph A. M. Holtum A C and Klaus Winter BA School of Marine and Tropical Biology, James Cook University, Townsville, Qld 4811, Australia.
B Smithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Ancon, Republic of Panama.
C Corresponding author. Email: joseph.holtum@jcu.edu.au
Functional Plant Biology 37(8) 694-702 https://doi.org/10.1071/FP10001
Submitted: 2 January 2010 Accepted: 30 March 2010 Published: 26 July 2010
Abstract
Studies of responses of forest vegetation to steadily increasing atmospheric concentrations of CO2 have focussed strongly on the potential of trees to absorb extra carbon; the effects of elevated [CO2] on plant–soil water relations via decreased stomatal conductance and increased ambient temperature have received less attention, but may be significant in the long term at the ecosystem level. CO2 augmentation experiments with young trees demonstrate small increases in aboveground carbon content, but these increases tend to diminish as trees get older. By contrast, several experiments suggest continued decreases in transpiration and increased soil water content under these conditions. In tropical forests, the major cause of increases in aboveground biomass observed in the recent past is not necessarily elevated [CO2]. Undoubtedly, the potential of monitoring trees in forest dynamics plots to deduce CO2-specific alterations in forest structure and standing biomass will unfold in the decades to come. The comprehensive understanding of responses of forest vegetation to elevated [CO2] in the Anthropocene will depend upon the inclusion of detailed measurements of soil water pools and water fluxes through the soil–plant–atmosphere continuum in future tree CO2 augmentation experiments and forest dynamics plot studies.
Additional keywords: climate change, carbon sequestration, evapotranspiration, FACE (free air CO2 enrichment), water use efficiency.
Acknowledgements
Neal Smith, STRI Emeritus Scientist, persistently prodded us to write this. Support is acknowledged from the Smithsonian Tropical Research Institute (KW and JAMH), the JCU Special Studies Program (JAMH) and the Reverend Dr RG Dunn (JAMH).
Ainsworth EA, Long SP
(2005) What have we learned from 15 years of free-air CO2 enrichment (FACE)? A meta-analytic review of the responses of photosynthesis, canopy properties and plant production to rising CO2. New Phytologist 165, 351–372.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
[Verified 15 June 2010]
Nowak RS,
Ellsworth SD, Smith SD
(2004) Functional responses of plants to elevated atmospheric CO2 – do photosynthetic and productivity data from FACE experiments support early predictions? New Phytologist 162, 253–280.
| Crossref | GoogleScholarGoogle Scholar |
Oren R,
Ellsworth DS,
Johnsen KH,
Phillips N, Ewers BE ,
et al
.
(2001) Soil fertility limits carbon sequestration by forest ecosystems in a CO2-enriched atmosphere. Nature 411, 469–472.
| Crossref | GoogleScholarGoogle Scholar |
CAS |
PubMed |
Phillips OL,
Lewis SL,
Baker TR,
Chao KJ, Higuchi N
(2008) The changing Amazon forest. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences 63, 1819–1827.
| Crossref | GoogleScholarGoogle Scholar |
Phillips OL,
Aragao LEOC,
Lewis SL,
Fisher JB, Lloyd J ,
et al
.
(2009) Drought sensitivity of the Amazon rainforest. Science 323, 1344–1347.
| Crossref | GoogleScholarGoogle Scholar |
CAS |
PubMed |
Piao S,
Friedlingsstein P,
Ciais P,
de Noblet-Ducoudré N,
Labat D, Zaehle S
(2007) Changes in climate and land use have a larger direct impact than rising CO2 on global river runoff trends. Proceedings of the National Academy of Sciences of the United States of America 104, 15 242–15 247.
| Crossref | GoogleScholarGoogle Scholar |
CAS |
PubMed |
Reich PB,
Hobbie SE,
Lee T,
Ellsworth DS,
West JB,
Tilman D,
Knops JMH,
Naeem S, Trost J
(2006) Nitrogen limitation constrains sustainability of ecosystem response to CO2. Nature 440, 922–925.
| Crossref | GoogleScholarGoogle Scholar |
CAS |
PubMed |
Rey A, Jarvis PG
(1997) Long term effects of elevated atmospheric CO2 concentration on growth and physiology of birch (Betula pedula Roth.). Botanical Journal of Scotland 49, 325–340.
| Crossref | GoogleScholarGoogle Scholar |
Rolim SG,
Jesus RM,
Nascimento HEM,
do Couto HTZ, Chambers JQ
(2005) Biomass change in an Atlantic tropical moist forest: the ENSO effect in permanent sample plots over a 22-year period. Oecologia 142, 238–246.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
Saurer M,
Cherubini P,
Bonani G, Siegwolf R
(2003) Tracing carbon uptake from a natural CO2 spring into tree rings: an isotope approach. Tree Physiology 23, 997–1004.
|
CAS |
PubMed |
Saxe H,
Ellsworth DS, Heath J
(1998) Tree and forest functioning in an enriched CO2 atmosphere. New Phytologist 139, 395–436.
| Crossref | GoogleScholarGoogle Scholar |
Seiler TJ,
Rasse DP,
Li JH,
Dijkstra P,
Anderson HP,
Johnson DP,
Powell TL,
Hungate BA,
Hinkle CR, Drake BG
(2009) Disturbance, rainfall and contrasting species responses mediated aboveground biomass response to 11 years of CO2 enrichment in a Florida scrub-oak ecosystem. Global Change Biology 15, 356–367.
| Crossref | GoogleScholarGoogle Scholar |
Sellers PJ,
Bounoua L,
Collatz GJ,
Randall DA, Dazlich DA ,
et al
.
(1996) Comparison of radiative and physiological effects of doubled atmospheric CO2 on climate. Science 271, 1402–1406.
| Crossref | GoogleScholarGoogle Scholar |
CAS |
Sharma P,
Sober A,
Sober J,
Podila GK,
Kupisky ME,
Mattson WJ,
Isebrands JG, Karnosky DF
(2003) Moderation of [CO2]-induced gas-exchange responses by elevated O3 in trembling aspen and sugar maple. Ekologia 122, 318–331.
Sitch S,
Huntingford C,
Gedney N,
Levy PE, Lomas M ,
et al
.
(2008) Evaluation of the terrestrial carbon cycle, future plant geography and climate-carbon cycle feedbacks using five dynamic global vegetation models (DGVMs). Global Change Biology 14, 2015–2039.
| Crossref | GoogleScholarGoogle Scholar |
Sotta ED,
Veldkamp E,
Schwendenmann L,
Guimaraes BR,
Paixao RK,
Ruivo MDLP,
Lola da Costa AC, Meir P
(2007) Effects of an induced drought on soil carbon dioxide (CO2) efflux and soil CO2 production in an Eastern Amazonian rainforest, Brazil. Global Change Biology 13, 2218–2229.
| Crossref | GoogleScholarGoogle Scholar |
Stork NE,
Balston J,
Farquhar GD,
Franks PJ,
Holtum JAM, Liddell MJ
(2007) Tropical rainforest canopies and climate change: a commentary. Austral Ecology 32, 105–112.
| Crossref | GoogleScholarGoogle Scholar |
Tognetti R,
Longobucco A,
Miglietta F, Raschi A
(1998) Transpiration and stomatal behaviour of Quercus ilex plants during the summer in a Mediterranean carbon dioxide spring. Plant, Cell & Environment 21, 613–622.
| Crossref | GoogleScholarGoogle Scholar |
Tognetti R,
Longobucco A,
Miglietta F, Raschi A
(1999) Water relations, stomatal response and transpiration of Quercus pubescens trees during summer in a Mediterranean carbon dioxide spring. Tree Physiology 19, 261–270.
| PubMed |
Tognetti R,
Cherubini P, Innes JL
(2000) Comparative stem-growth rates of mediterranean trees under background and naturally enhanced ambient CO2 concentrations. New Phytologist 146, 59–74.
| Crossref | GoogleScholarGoogle Scholar |
Trenberth KE, Hoar TJ
(1997) El Niño and climate change. Geophysical Research Letters 24, 3057–3060.
| Crossref | GoogleScholarGoogle Scholar |
Tricker PJ,
Trewin H,
Kull O,
Clarkson GJJ,
Eensalu E,
Tallis MJ,
Colella A,
Doncaster CP,
Sabatti M, Taylor G
(2005) Stomatal conductance and not stomatal density determines the long-term reduction in leaf transpiration of poplar in elevated CO2. Oecologia 143, 652–660.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
Uddling J,
Teclaw RM,
Pregitzer KS, Ellsworth DS
(2009) Leaf and canopy conductance in aspen and aspen-birch forests under free air enrichment of carbon dioxide and ozone. Tree Physiology 29, 1367–1380.
| Crossref | GoogleScholarGoogle Scholar |
CAS |
PubMed |
Winter K,
Garcia M,
Lovelock CE,
Gottsberger R, Popp M
(2000) Responses of model communities of two tropical tree species to elevated atmospheric CO2: growth on unfertilized soil. Flora 195, 281–302.
Winter K,
Garcia M,
Gottsberger R, Popp M
(2001a) Marked growth response of communities of two tropical tree species to elevated CO2 when soil nutrient limitation is removed. Flora 196, 47–58.
Winter K,
Aranda J,
Garcia M,
Virgo A, Paton SR
(2001b) Effect of elevated CO2 and soil fertilization on whole-plant growth and water-use in seedlings of a tropical pioneer tree, Ficus insipida Willd. Flora 196, 458–464.
Wright SJ
(2005) Tropical forests in a changing environment. Trends in Ecology & Evolution 20, 553–560.
| Crossref | GoogleScholarGoogle Scholar |
Wright SJ
(2006) Response to Lewis et al.: the uncertain response of tropical forests to global change. Trends in Ecology & Evolution 21, 174–175.
| Crossref | GoogleScholarGoogle Scholar |
Wullschleger SD, Norby RJ
(2001) Sap velocity and canopy transpiration in a sweetgum stand exposed to free-air CO2 enrichment (FACE). New Phytologist 150, 489–498.
| Crossref | GoogleScholarGoogle Scholar |
Wullschleger SD,
Gunderson CA,
Hanson PJ,
Wilson KB, Norby RJ
(2002) Sensitivity of stomatal and canopy conductance to elevated CO2 concentration – interacting variables and perspectives of scale. New Phytologist 153, 485–496.
| Crossref | GoogleScholarGoogle Scholar |
CAS |
Yeh S-W,
Kug J-S,
Dewitte B,
Kwon M-H,
Kirtman BP, Jin F-F
(2009) El Niño in a changing climate. Nature 461, 511–514.
| Crossref | GoogleScholarGoogle Scholar |
CAS |
PubMed |
Zotz G,
Harris G,
Königer M, Winter K
(1995) High rates of photosynthesis in the tropical pioneer tree, Ficus insipida Wild. Flora 190, 265–272.