13 - Nutrients: Dynamics and Limitations

Abstract

This chapter discusses the constraints on the impact of atmospheric carbon dioxide and interactions between carbon and other living organisms. Carbon is, leaving oxygen aside, the quantitatively most important element in living organisms. An increasing availability of this element through an increasing atmospheric carbon dioxide concentration is therefore expected to have a direct impact on organisms. The constraints are basically of two kinds: the extent to which different components in an ecosystem can adjust the element ratios, ecosystem stoichiometry, that is, how flexible are plant and soil C:N ratios; and the extent to which an increasing availability of one element can change the availability of other elements, that is, if an increase in carbon dioxide concentration can increase the retention of nitrogen in the ecosystem. Stoichiometry places constraints on the amount of carbon stored in ecosystems. From the perspective of carbon-nitrogen interactions, there are three ways in which the amount of carbon in the ecosystem can change: Change the total amount of nitrogen in the ecosystem while maintaining C:N ratios; Change the C:N ratios of the ecosystem components; and change the distribution of nitrogen among ecosystem components.