Fine roots are part of the regenerative system of trees. The annual renewal of fine roots can represent an important sink for assimilates in forest ecosystems (Agren et al. 1980). Estimates for the production of fine roots range between 5 and 70% of the total net primary production of trees (Santantonio 1990). Thus, fine root turnover may equal or even exceed the amount of carbon that is required for foliar litter production, making the quantification of fine root turnover an essential component of carbon budgets in forest ecosystems (Bartelink 1998). However, only limited data are available on belowground C allocation as it is not possible to directly measure root growth, mortality and decomposition in an undisturbed forest soil. Even less is known about the factors controlling fine root turnover. Because of the insufficient database, reliable hypotheses about the regulation of belowground processes in forest ecosystems have great uncertainty (Vogt et al. 1996). However, due to their importance in global climate change, more information on the factors controlling carbon allocation within plants is required to assess the ability of forest ecosystems to sequester carbon (Kroon and Visser 2003). The emphasis of the present chapter is to assess if soil acidification affects the fine root production or turnover of European beech. In addition to the quantification of carbon cycling via fine root dynamics, the importance of fine root litter production in element recycling and thus the soil organic matter pool will be evaluated.