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Vines -- Summary
There have been very few studies of the effects of elevated concentrations of atmospheric CO2 on the growth of vines.  Three early investigations were those of Lakso et al. (1986), Gamon and Pearcy (1989) and Condon et al. (1992), all of which documented large positive effects of elevated CO2 on vine photosynthesis.  One of the more recent of such studies that we have reviewed on our website was conducted by Greaves and Buwalda (1996), who grew kiwifruit (Actinidia deliciosa) vines in controlled environment chambers maintained at ambient and enriched (ambient plus 200 ppm) atmospheric CO2 concentrations for three full growing seasons.  Their experiment revealed that leaves of vines growing in ambient air displayed a daily decline in photosynthetic rate beginning around nine o'clock in the morning.  In contrast, leaves of vines growing in CO2-enriched air exhibited no signs of photosynthetic depression and continued to display increasing photosynthetic rates as time progressed and light intensity and temperature rose towards midday and later.  In fact, during periods of peak irradiance and warmth, the photosynthetic rates of the vines that experienced the experiment's 55% increase in atmospheric CO2 concentration were 75% greater than those of the vines growing in ambient air.

A second vine study we have reviewed was conducted by Granados and Korner (2002), who grew three tropical understory vines (Gonolobus cteniophorus, Ceratophytum tetragonolobum and Thinouia tomocarpa) for seven months in controlled environment chambers maintained at atmospheric CO2 concentrations of 280, 420, 560 and 700 ppm in combination with high and low light intensities.  In their experiment, plant biomass increased with atmospheric CO2 concentration from 280 to 560 ppm in all three vines, and continued to increase up to 700 ppm in all species except Gonolobus, the fastest growing of the three.  On average, plant biomass was 61% greater at high light than it was at low light.  However, the greatest CO2-induced growth responses in each species occurred in the low light environment.  Increasing the atmospheric CO2 concentration from 280 to 420 ppm, for example, increased Gonolobus plant biomass by 32% in high light but by 85% in low light, while it increased Ceratophytum plant biomass by 24% in high light but by a whopping 249% in low light.  Last of all, in Thinouia, the same CO2 increase actually decreased plant biomass by 1% in high light but increased it by 65% in low light.

Most recently, Smart (2004) monitored CO2 and O2 exchange rates from grapevine cane wood under steady-state conditions after the CO2 concentration of the air around the cane tissue was abruptly raised and then held constant at the new concentration for periods of several hours.  This protocol revealed that elevated CO2 decreased dark respiration by about 6% when the atmospheric CO2 concentration was raised from 300 to 750 ppm and by a further 5% when it was increased from 750 to 2000 ppm.  Consequently, in light of these CO2-induced decreases in wood respiration, there is every reason to believe that the large positive effects of atmospheric CO2 enrichment on leaf net photosynthesis discovered in the experiments described above will truly lead to large increases in vine growth as the air's CO2 content continues to rise.

What are the ramifications of these results?  Would you believe the destruction of earth's tropical forests?  Yes, it's true … not that tropical trees are about to be strangled by rampaging vines gone wild, but that there are people who will put a negative twist on almost any positive consequence of atmospheric CO2 enrichment; and the case in point is no exception.

Based on data from several unique, long-term, multi-regional studies of liana and tree populations, Phillips et al. (2002) tested the specific prediction that lianas experienced enhanced growth over the last two decades of the 20th century.  Analyzing reams of observations acquired from 47 interior-forest sites in four Amazonian regions (North Peru, South Peru, Bolivia and Ecuador), they found that non-fragmented Amazon forests have indeed seen significant increases in the density, basal area and mean size of climbing woody vines, and that "over the last two decades of the twentieth century the dominance of large lianas relative to trees has increased by 1.7-4.6% a year."

What is driving this change?  In asking themselves this question, Phillips et al. describe "the degree of internal consistency within and between data sets across differing sample unit sizes, target variables, minimum plant sizes, climatic regimes, edaphic conditions, regional locations and spatial scales," noting that these ubiquitous observations suggest a widespread phenomenon is at work and that the historical rise in the air's CO2 content is thus a logical candidate for being the ultimate cause of the phenomenon.  We agree; but with respect to what they believe this phenomenon portends for the future, we disagree.

Noting that the presence of lianas can substantially suppress tree growth, as indicated by Laurance et al. (2001) and Schnitzer and Bongers (2002), Phillips et al. say the rapid and possibly-CO2-induced increase in liana growth "implies that the tropical terrestrial carbon sink may shut down sooner than current models suggest," as CO2-enhanced liana growth begins to negatively impact contemporary tree growth.  Other observations, however - many from Phillips himself - suggest that tropical trees may well be rising to the liana challenge and will not succumb to the increasing size and presence of the parasitic vines.

For starters, Phillips et al. note that ecological orthodoxy suggests that old-growth forests should be close to dynamic equilibrium; and for many years, this appeared to be the case.  Recently, however, earth's ancient forests seem to have acquired a new lease on life and have become much more productive.

In one of the first studies to illuminate this new reality, Phillips and Gentry (1994) analyzed the turnover rates - which are close correlates of net productivity (Weaver and Murphy, 1990) - of forty tropical forests from around the world.  They found that the growth rates of these already highly productive forests have been rising even higher since at least 1960, with an apparent pantropical acceleration since 1980, the period of time over which Phillips et al. say liana growth has also accelerated, which suggests that the latter phenomenon has not been an impediment to the former.

Phillips et al. additionally note that several subsequent studies have verified that neotropical forests are indeed accumulating both carbon (Grace et al., 1995; Malhi et al., 1998) and biomass (Phillips et al., 1998, 2002), "possibly in response to the increasing atmospheric concentrations of carbon dioxide (Prentice et al., 2001; Malhi and Grace, 2000)."  Consequently, it would appear that tropical trees and their parasitic lianas are both being benefited by the ongoing rise in the air's CO2 content, with the ultimate consequence that rather than having the tropical terrestrial carbon sink "shut down" in the near future, we can expect it to continue to gradually increase in magnitude.

Yes, one plant's good fortune need not come at the expense of another.  The rising tide of earth's atmospheric CO2 concentration will likely lift the vast majority of all plants to new heights of productivity.

References
Condon, M.A., Sasek, T.W. and Strain, B.R.  1992.  Allocation patterns in two tropical vines in response to increased atmospheric CO2Functional Ecology 6: 680-685.

Gamon, J.A. and Pearcy, R.W.  1989.  Leaf movement, stress avoidance and photosynthesis in Vitis californicaOecologia 79: 475-481.

Grace, J., Lloyd, J., McIntyre, J., Miranda, A.C., Meir, P., Miranda, H.S., Nobre, C., Moncrieff, J., Massheder, J., Malhi, Y., Wright, I. and Gash, J.  1995.  Carbon dioxide uptake by an undisturbed tropical rain-forest in Southwest Amazonia, 1992-1993.  Science 270: 778-780.

Granados, J. and Korner, C.  2002.  In deep shade, elevated CO2 increases the vigor of tropical climbing plants.  Global Change Biology 8: 1109-1117.

Greaves, A.J. and Buwalda, J.G.  1996.  Observations of diurnal decline of photosynthetic gas exchange in kiwifruit and the effect of external CO2 concentration.  New Zealand Journal of Crop and Horticultural Science 24: 361-369.

Lakso, A.N., Reisch, B.I., Mortensen, J. and Roberts, M.H.  1986.  Carbon dioxide enrichment for stimulation of growth of in vitro-propagated grapevines after transfer from culture.  Journal of the American Society for Horticultural Science 111: 634-638.

Laurance, W.F., Perez-Salicrup, D., Delamonica, P., Fearnside, P.M., D'Angelo, S., Jerozolinski, A., Pohl, L. and Lovejoy, T.E.  2001.  Rain forest fragmentation and the structure of Amazonian liana communities.  Ecology 82: 105-116.

Malhi Y. and Grace, J.  2000.  Tropical forests and atmospheric carbon dioxide.  Trends in Ecology and Evolution 15: 332-337.

Malhi, Y., Nobre, A.D., Grace, J., Kruijt, B., Pereira, M.G.P., Culf, A. and Scott, S.  1998.  Carbon dioxide transfer over a Central Amazonian rain forest.  Journal of Geophysical Research 103: 31,593-31,612.

Phillips, O.L. and Gentry, A.H.  1994.  Increasing turnover through time in tropical forests.  Science 263: 954-958.

Phillips, O.L., Malhi, Y., Vinceti, B., Baker, T., Lewis, S.L., Higuchi, N., Laurance, W.F., Vargas, P.N., Martinez, R.V., Laurance, S., Ferreira, L.V., Stern, M., Brown, S. and Grace, J.  2002.  Changes in growth of tropical forests: Evaluating potential biases.  Ecological Applications 12: 576-587.

Phillips, O.L., Malhi, Y., Higuchi, N., Laurance, W.F., Nunez, P.V., Vasquez, R.M., Laurance, S.G., Ferreira, L.V., Stern, M., Brown, S. and Grace, J.  1998.  Changes in the carbon balance of tropical forests: Evidence from long-term plots.  Science 282: 439-442.

Phillips, O.L., Martinez, R.V., Arroyo, L., Baker, T.R., Killeen, T., Lewis, S.L., Malhi, Y., Mendoza, A.M., Neill, D., Vargas, P.N., Alexiades, M., Ceron, C., Di Fiore, A., Erwin, T., Jardim, A., Paiacios, W., Saidias, M. and Vinceti, B.  2002.  Increasing dominance of large lianas in Amazonian forests.  Nature 418: 770-774.

Prentice, I.C., Farquhar, G.D., Fasham, M.J.R., Goulden, M.L., Heimann, M., Jaramillo, V.J., Kheshgi, H.S., Le Quere, C., Scholes, R.J., Wallace, D.W.R., Archer, D., Ashmore, M.R., Aumont, O., Baker, D., Battle, M., Bender, M., Bopp, L.P., Bousquet, P., Caldeira, K., Ciais, P., Cox, P.M., Cramer, W., Dentener, F., Enting, I.G., Field, C.B., Friedlingstein, P., Holland, E.A., Houghton, R.A., House, J.I., Ishida, A., Jain, A.K., Janssens, I.A., Joos, F., Kaminski, T., Keeling, C.D., Keeling, R.F., Kicklighter, D.W., Hohfeld, K.E., Knorr, W., Law, R., Lenton, T., Lindsay, K., Maier-Reimer, E., Manning, A.C., Matear, R.J., McGuire, A.D., Melillo, J.M., Meyer, R., Mund, M., Orr, J.C., Piper, S., Plattner, K., Rayner, P.J., Sitch, S., Slater, R., Taguchi, S., Tans, P.P., Tian, H.Q., Weirig, M.F., Whorf, T. and Yool, A.  2001.  The carbon cycle and atmospheric carbon dioxide.  Chapter 3 of the Third Assessment Report of the Intergovernmental Panel on Climate Change.  Climate Change 2001: The Scientific Basis.  Cambridge University Press, Cambridge, UK, pp. 183-238.

Schnitzer, S.A. and Bongers, F.  2002.  The ecology of lianas and their role in forests.  Trends in Ecology and Evolution 17: 223-230.

Smart, D.R.  2004.  Exposure to elevated carbon dioxide concentration in the dark lowers the respiration quotient of Vitis cane wood.  Tree Physiology 24: 115-120.

Weaver, P.L. and Murphy, P.G.  1990.  Forest structure and productivity in Puerto Rico's Luquillo Mountains.  Biotropica 22: 69-82.