Total Storage and Landscape Partitioning of Soil Organic Carbon and Phytomass Carbon in Siberia

Abstract:

We present results of detailed partitioning of soil organic carbon (SOC) and phytomass carbon (PC) from two study sites in Siberia. The study sites in the Tundra (Kytalyk) and the Taiga (Spasskaya Pad) reflect two contrasting environments in the continuous permafrost zone. In total 57 individual field sites (24 and 33 per study site respectively) have have been sampled for SOC and PC along transects cutting across different land covers. In Kytalyk the sampling depth for the soil pedons was 1 m depth. In Spasskaya Pad where the active layer was significantly deeper, we aimed for 2 m depth or tried to include at least the top of the permafrost. Here the average depth of soil profiles was 152 cm. PC was sampled from 1x1 m ground coverage plots. In Spasskaya Pad tree phytomass was also estimated on a 5x5 m plot. The SOC storage was calculated separately for the intervals 0-30 cm, 30-100 cm and 100-200 cm (the latter only for Spasskaya Pad), as well as for organic layer vs. mineral soil, active layer vs. permafrost and for cryoturbated soil horizons. Landscape partitioning was performed by thematic up-scaling using a vegetation based land cover classification of very high resolution (2x2 m) satellite imagery.

Non-Metric Multidimensional Scaling (NMDS) was used to explore the relationship of SOC with PC and different soil and permafrost related variables. The results show that the different land cover classes can be considered distinct storages of SOC, but that PC is not significantly related to total SOC storage. At both study sites the 30-100 cm SOC storage is more important for the total SOC storage than the 0-30 cm interval, and large portions of the total SOC are stored in the permafrost. The largest contribution comes from wetland pedons, but highly cryoturbated individual non-wetland pedons can match these. In Kytalyk the landscape partitioning of SOC mostly follows large scale geomorphological features, while in Spasskaya pad forest type also has a large influence.