Mountainous terrain defines many dryland regions and results in pronounced variation in soil thickness and soil organic carbon (SOC) stocks that is not currently captured by carbon and global climate models. Here we quantify how total profile SOC varies with topographic morphometry, aspect and curvature, to estimate SOC storage within a 1.8 km2 granite-dominated catchment in Idaho, U.S.A. We show that north-facing soil pits have on average 2.9 times more total SOC per area than the south-facing sites, and convergent soil pits have on average 6.4 times more total SOC per area compared to divergent sites. Curvature explained 91% of variation in total profile SOC at a 3-m resolution when the entire vertical dimension of SOC was determined. Catchment SOC stocks were determined from this curvature-SOC model and showed that SOC below 0.3 m depth accounted for >50% of the catchment total SOC, indicating substantial underestimation of SOC stocks if only sampled at shallower depths. We conclude that processes responsible for carbon sequestration in soils vary spatially at relatively small scales, and they can be described in a deterministic fashion given adequate elevation data.
Pedotransfer functions (PTFs) have been developed to estimate soil bulk density (BDFF) using the relationships with soil organic carbon content (SOC) and particle size distribution. Current PTF’s implicitly assume that coarse fraction (CF) content and lithology do not influence BDFF. In this study, we examine the influence of CF content and lithology on BDFF estimates by developing PTF’s for total bulk density (BDT), which includes both fine and coarse fragments, using measured SOC in soils derived from felsic and mafic lithologies (148 felsic and 64 mafic, 212 total). Our results show that SOC is highly correlated with BDT in soils derived from felsic (r2 value of 0.79, p2 value of 0.84, p 2 mm), and we adjust BDT with soil pedon CF content to determine fine fraction bulk densities (BDFF-CFadj). A validation subset of 70 samples was used to compare our model against 23 published PTFs. When BDT is corrected for CF, which is highly variable vertically and horizontally within the watershed, we observe substantial improvements (average of 10.05 ± 4.89 %) in BDFF-CFadj estimation and associated errors compared to other PTFs. Findings from our study demonstrate that incorporation of CF and lithology into BDFF estimations can substantially improve BDFF and consequently soil carbon stock estimates.
Reynolds Creek, soil organic carbon, soil thickness, curvature, topography
XML is in ISO-19115 geographic metadata format, compatible with ESRI Geoportal Server.
Citation for This Dataset
Patton, Nicholas R.; Lohse, Kathleen A.; Godsey, Sarah E.; Parsons, Susan B.; and Seyfried, Mark S.. (2018). Dataset for Topographic Controls on Total Soil Organic Carbon in Semi-arid Environments [Data set]. Retrieved from https://doi.org/10.18122/B2XT55
Citation for This Webpage
Patton, N.R.; Lohse, K.A.; Godsey, S.E.; Parsons, S.B.; Seyfried, M.S. (2016). "CZO Dataset: Johnston Draw - Soil Biogeochemistry, Soil Survey, Topographic Carbon Storage (2014-2016) - soil organic carbon, bulk density." Retrieved 18 Feb 2019, from http://criticalzone.org/reynolds/data/dataset/6488/
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