C1 aims at addressing the impact of the two major driving factors climate change and land-use change on soil OC and N storage, its variability, and cycling. To assess the impact of these two factors on the TP we will identify a permafrost gradient in the two catchments in the Nam Co area that can serve as a space-for-time substi-tution approach of soils with different permafrost regimes and of different grazing intensity. LUH and LU will carry out a detailed OC and total N mapping using nested grids in the soils of the different permafrost regimes and under different grazing intensity, followed by a geostatistical assessment (Spielvogel et al., 2009). Soil and soil organic matter will be further fractionated into functionally different pools using the density fractionation scheme of Cerli et al. (2012), and turnover times of OC will be estimated by 14C analysis at MPI-BGC Jena.
Organic C, i.e. the source of heterotrophic activity, in Nam Co is not only of autochthonous origin but also from allochthonous origin. Therefore, LUH will assess dissolved organic matter (DOM) in the fluvial systems in the two catchments using the gauges installed by S1. Assessment of rivers draining subcatchments will allow analyzing the impact of different environmental conditions to the DOM leaving the terrestrial system. Glacier, lake, river, and soil waters will be analyzed for DOC, DIC and dissolved organic nitrogen (DON) concentrations, as well as qualitative parameters of DOM. δ13C and δ15N of DOM, contents of sugars, amino acids, and lignin as well as UV and fluorescence spectroscopy will inform about the chemical composition and the microbial processing of DOM (Amon et al., 2012). This information will be related the decomposability of DOM (Kalbitz et al., 2003; Kawahigashi et al., 2004) as measured by O2 consumption.
At selected sites, LU will carry out 13C pulse-labeling experiments to identify the input pattern of plant-derived OC to the soil, depending on permafrost regime and land management (Hafner et al., 2012; Shibistova et al., 2012). A high-frequency measurement of soil CO2 efflux rates together with the δ13C ratio of the CO2 will allow separation of autotrophic and heterotrophic respiration in soil. With a consequent use of a double isotope approach (13C labeling, 14C in soil organic matter and CO2), jointly with C2 we will be able to assess both, the fast and the slow cycling of organic matter within the different pools.
Prof. Dr. Guggenberger, LU Hannover
Dr. Carlos Sierra, MPI Jena
Prof. Dr. Tsechoe Dorji, ITP Lhasa
Prof. Dr. Li Xiaogang, Lanzhou University