Spatial Heterogeneity and Environmental Controllers of Permafrost Region Soil Organic Carbon Stocks
We used geospatial analysis, field observations, and high-resolution environmental factor datasets representing soil-forming factors to predict soil carbon stocks in the top 3 m of northern hemisphere permafrost region soils. The greatest prediction uncertainties were found in toe-slope positions of the circumpolar region and in flat areas of the Tibetan region. We found that soil wetness and elevation are the dominant topographic controllers of permafrost region soil carbon stocks. Surface air temperature was the dominant controller of the circumpolar region and precipitation was a significant climatic controller of Tibetan region soil carbon stocks.
Using a new database of field observations and environmental factors, this study predicted high-resolution spatial distribution of organic carbon stocks in northern hemisphere permafrost region soils. We identified land cover types, topographic positions, and climatic zones where the predicted soil carbon stocks and associated uncertainties are highest and lowest. We identified dominant environmental predictors of soil carbon stocks of different permafrost regions and depth intervals. Our spatially explicit estimates of soil carbon stocks will be crucial for initializing and benchmarking soil carbon representations in land surface models used to quantify the permafrost carbon feedback. Our results also help prioritize sampling strategies that aim to reduce uncertainty in permafrost soil carbon stocks.
Large stocks of organic carbon have accumulated in the northern hemisphere permafrost region soils, but their current magnitude and future fate remain uncertain. Using a new database of soil profiles, high-resolution environmental factor observations, and a geospatial framework, we generated spatially explicit estimates of permafrost-region soil carbon stocks, quantified prediction uncertainties, and identified key environmental predictors. We estimated 1014 Pg C stored in the top 3 m of northern hemisphere permafrost region soils. The greatest uncertainties were found in toe-slope positions of the northern circumpolar region and in flat areas of the Tibetan region. We found that soil wetness and elevation were the dominant topographic controllers of permafrost region soil carbon stocks. Surface air temperature and precipitation were significant climatic controllers of soil carbon stocks in the northern circumpolar and Tibetan permafrost regions, respectively. Our results provide the first high-resolution geospatial assessment of permafrost region soil carbon stocks and their relationships with environmental factors. This information is crucial for modeling the response of permafrost-affected soils to changing climate.