The Turnover of Protons by Mineralization and Ion Uptake in a Beech (Fagus Silvatica) and a Norway Spruce Ecosystem

Abstract

On the base of the flux balance of two forested ecosystems, the annual rates of mineralization within the humus layer and ion uptake are discussed in respect to H⁺ turnover. In both ecosystems (beech and spruce), ion uptake in mineral soil is connected with a strong H⁺ production in most years between 1971 and 1980. The rate of H⁺ production resulting from ion uptake is regulated by the NH₄/NO₃ ratio and is higher under spruce than under beech in accordance with this ratio. Assuming steady state conditions, the H⁺ production as a result of ion uptake is followed by an equivalent H⁺ consumption during mineralization. Nevertheless, the rate of H⁺ consumption during mineralization is, due to spatial and temporal discouplings of the ion cycle as well as due to the production of organic acids, less than the rate of H⁺ production resulting from ion uptake. Thus the sum of both processes leads to ecosystem internal H⁺ net production. The influence of the NH₄/NO₃ ratio during mineralization and ion uptake on the rate of ecosystem internal proton production is discussed.