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Soil Phosphorus Availability Can Be Enhanced in CO2-Enriched Air

Paper Reviewed
Huang, W., Zhou, G., Liu, J., Duan, H., Liu, X., Fang, X. and Zhang, D. 2014. Shifts in soil phosphorus fractions under elevated CO2 and N addition in model forest ecosystems in subtropical China. Plant Ecology 215: 1373-1384.

Introducing their study published in Plant Ecology, Huang et al. (2014) write that "phosphorus (P) often limits plant productivity and other ecosystem processes in tropical and subtropical forests," citing Vitousek et al. (2010) and Cleveland et al. (2011), because, as they continue, "in many highly weathered tropical and subtropical soils, a large proportion of total P is bound in organic compounds that are of limited biological availability to plants," citing Harrison (1987), in which cases they say the availability of P "largely depends on the turnover of organic P compounds as well as the rapid recycling of P from litterfall," as described by Attiwill and Adams (1993) and Turner (2008).

To explore this issue further, and to see how it might be affected by the continuing rise in the atmosphere's CO2 concentration, the seven Chinese scientists used open-top chambers to study changes in soil P fractions in model subtropical forests - each of which was comprised of eight seedlings from each of six dominant native tree species - after five years of exposure to elevated CO2 (700 ppm) and N addition (10 g N/m2/year).

This work revealed, as they describe it, that "elevated CO2 resulted in [1] greater soil P availability, as well as [2 ] more efficient P recycling from litterfall," both of which phenomena tended to facilitate plant growth. In addition, they discovered that [3] "the elevated CO2 could drive the mobilization of P from the recalcitrant P pool, and thereby maintain or even increase overall soil P availability," which could [4] "help to meet the increased plant P demand under N addition."

In light of these several findings, there would appear to be more reasons than ever to expect the vegetation growing on earth's tropical and subtropical soils to become ever more productive as the atmosphere's CO2 concentration continues its historical upward trend.

Attiwill, P.M. and Adams, M.A. 1993. Nutrient cycling in forests. New Phytologist 124: 561-582.

Cleveland, C.C., Townsend, A.R., Taylor, P., Alvarez-Clare, S., Bustamante, M.M.C., Chuyong, G., Dobrowski, S.Z., Grierson, P., Harms, K.E., Houlton, B.Z., Marklein, A., Parton, W., Porder, S., Reed, S.C., Sierra, C.A., Silver, W.L., Tanner, E.V.M. and Wieder, W.R. 2011. Relationships among net primary productivity, nutrients and climate in tropical rain forest; a pan-tropical analysis. Ecology Letters 14: 939-947.

Harrison, A.F. 1987. Soil Organic Phosphorus: A Review of World Literature. CAB International, Wallingford, England.

Turner, B.L. 2008. Resource partitioning for soil phosphorus: a hypothesis. Journal of Ecology 96: 698-702.

Vitousek, P.M., Porder, S., Houlton, B.Z. and Chadwick, O.A. 2010. Terrestrial phosphorus limitation: mechanisms, implications, and nitrogen-phosphorus interactions. Ecological Applications 20: 5-15.

Posted 3 March 2015