, Volume 1, Issue 3, pp 219-232

Physiological and ecological controls on carbon sequestering in terrestrial ecosystems

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Abstract

Carbon cycling processes in ecosystems are generally believed to be well understood. Carbon, hydrogen, oxygen and other essential elements are chemically converted from inorganic to organic compounds primarily in the process of photosynthesis. Secondary metabolic processes cycle carbon in and among organisms and carbon is ultimately released back to the environment as CO2 by respiratory processes. Unfortunately, our understanding of this cycle was determined under the assumption that the primary inorganic form of C (CO2 in the atmosphere) was relatively constant. With the emerging concensus that atmospheric carbon concentration is increasing, we must now reassess our understanding of the carbon cycle. How will plants, animals and decomposers respond to a doubling of carbon supply? Will biological productivity be accelerated? If plant productivity increases will a predictable percentage of the increase be accumulated as increased standing crop? Or, is it possible that doubling the availability of CO2 will increase metabolic activity at all trophic levels resulting in no net increase in system standing crop? The purpose of this paper is to review evidence for physiological and growth responses of plants to carbon dioxide enhancement. Essentially no research has been completed on the ecological aspects of these questions. From this review, I conclude that accurate predictions of future ecosystem responses to increasing atmospheric carbon dioxide concentration are not possible without additional understanding of physiological and ecological mechanisms.