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Chapter 12Is There a Theoretical Limit to Soil Carbon Storage in Old-Growth Forests? A Model Analysis with Contrasting Approaches Apart from the intrinsic worth that nature and forests have due merely to their existence, old-growth forests have always provided a number of additional values through their function as regulators of the water cycle | Chapter 12 Is There a Theoretical Limit to Soil Carbon Storage in Old-Growth Forests A Model Analysis with Contrasting Approaches Markus Reichstein Goran I. Agren and Sebastien Fontaine 12.1 Introduction Apart from the intrinsic worth that nature and forests have due merely to their existence old-growth forests have always provided a number of additional values through their function as regulators of the water cycle repositories of genetic and structural biodiversity and recreational areas see e.g. Chaps. 2 Wirth et al. 16 Armesto et al. and 19 Frank et al. this volume . In the context of climate change mitigation carbon sequestration has become another highly valued function of natural and managed ecosystems. In this context the carbon sequestration potential of old-growth forests has often been doubted and contrasted with the high sequestration potential of young and short-rotation forests although there can be substantial carbon losses from forest soils following clear-cutting cf. Chap. 21 by Wirth this volume . The question of long-term carbon uptake by old-growth forests has lead to much scientific debate between the modelling and experimental communities in the past. Classical soil carbon turnover models favoured by certain factions of the modelling community where soil carbon is distributed among different pools and decays according to first-order kinetics with pool-specific turnover constants logically lead to steady state situations. Here the total input equals the total efflux of carbon and there cannot be a long-term uptake of carbon by ecosystems. However this theoretical deduction from first-order kinetic pool models seems to contradict a number of observations where long-term carbon uptake has been perceived or at least cannot be excluded Schlesinger 1990 and see Chap. 11 by Gleixner et al. this volume . This mostly theoretical chapter will address this apparent contradiction from a more conceptual modelling point of view. A number of modelling .
