Soil-Water Interface: Organic Matter Matters

  • 2016/05/30     Dresden, Germany


    Dissolved organic matter plays a critical role in linking soils and aquatic systems. Although it makes up a very small fraction (0.04% to 0.22%) of soil composition, its mass is not representative of its importance in the ecosystem. In reality, tracing the properties of dissolved organic matter during its passage through terrestrial and aquatic systems helps unlock major insights on what drives organic matter dynamics. By conceiving ecosystems and landscapes not as comprising of isolated sub-units but as a continuum of terrestrial and aquatic components, we better understand how dissolved organic matter bridges the two.

    Consistent with the Nexus Approach, there is a need to strengthen the soil-water nexus perspective in order to make better sense of the underpinnings of the ecosystem and to be able to better understand and eventually manage these resources especially in face of human and natural impacts on ecosystems. Speaking on Organic Matter Dynamics at the Interface of Soil and Water: A Soil Science Perspective, Prof. Dr. Karsten Kalbitz from the Institute of Soil Science and Site Ecology of Technische Universität Dresden (TU Dresden) reiterated the strong need for integrating the analysis of coupled terrestrial-aquatic ecosystems.

    Prof. Kalbitz shed light on carbon fluxes and their dynamics within the carbon cycle from a soil science perspective and went on to make the link between organic matter dynamics and physical processes of the carbon cycle affecting soil and water. Touching on the effects of disturbances on riverine dissolved organic carbon, he established that where there is a higher disturbance, organic matter makes up the main contributor. Discussing the variability of dissolved organic carbon fluxes, Prof. Kalbitz distinguished between the topsoil where variance is dominated by short temporal processes (e.g. changing seasons/weather conditions, land-use change, different management practices) and the subsoil that is affected by processes with longer temporal scales (e.g. climate change) and where there is an increasing importance of small scale spatial variability. Adding the dimension of water fluxes and considering their effects on dissolved organic carbon concentrations, it is established that the latter declines from topsoil to subsoil where high water fluxes results in the dilution of dissolved organic carbon. Water fluxes control carbon fluxes. Studying these dynamics reveals how the exchange between terrestrial and aquatic components determines functionality.

    Prof. Kalbitz spoke within the context of the 11th installation of the Nexus Seminar Series on 23 May 2016 at TU Dresden. The next Nexus Seminar on Water in the Nexus Approach will take place on 20 June 2016 at UNU-FLORES. All are welcome to join.