Loss of soil carbon to the atmosphere via inland surface waters

Abstract

Within the global carbon (C) cycle, there is still much debate as to the magnitude, location and turnover of the terrestrial C sinks (and sources). One of the major keys to closing this knowledge gap is that globally, the amount of C entering oceans maybe only ca. 33 % of the total C transported from terrestrial ecosystems to Inland surface waters. Streams, lakes, rivers and transitional waters are areas for the active transformation and recycling of terrestrially-derived C indirectly back to the atmosphere (estimated range of 25—44 %). Understanding processes that control soil C losses to and its fate in surface waters is not only important in establishing accuracy of C fluxes, feedbacks and tradeoffs but also providing evidence to limit terrestrial ecosystem C contributions to atmospheric carbon dioxide (CO2). The relationship between Inland surface waters and C cycling are controlled by biogeochemical, physical and hydrometeorological metrics that integrate both lateral (soil to water) and longitudinal (along the riverine continuum) processes during C transport in its different forms, i.e., particulate, dissolved and gaseous C species. This chapter outlines processes affecting compositional “quality” of C within surface waters and in-stream physico-chemical and biotic mechanisms that are instrumental to understanding losses of C via the soil-surface water-atmosphere pathway.