Soil Pedon Carbon and Nitrogen Data for Alaska: An Analysis and Update

Abstract

We combined C and N related pedon data from the USDA-NRCS National Cooperative Soil Survey Soil Characteriza tion Database with data from the University of Alaska Fairbanks (UAF) northern soils research program, representing 58 and 30 years of field work, respectively. Carbon and N data from 117 UAF pedons were added to 541 pedons from the USDA-NRCS data set for a total of 658. Missing carbon (C), nitrogen (N) and related data were added to nearly all of the USDA-NRCS Arctic region pedons from unpublished UAF data. We present relationships among soil parameters of the data set that are necessary for calculation of pedon soil organic C and N stores. These new relationships are nec essary for better estimating missing soil bulk density (Db) from measured soil organic C by high-temperature combus tion (SOC HTC ) and for conversion of acid chromate reduction soil organic carbon (SOC ACR ) to SOC HTC . For the USDA-NRCS data, missing Db data were estimated and SOC ACR corrected to SOC HTC using the new functional rela tionships developed. This allowed for pedon SOC and N stores to be calculated for 609 and 468 Alaska pedons respec tively, the most available to-date. Additionally, functional relationships were developed for data within soil orders to estimate total SOC HTC and N stores in pedons with missing surface organic horizons where only thicknesses were known. These relationships are presented in order to fill-in missing data and to better define the existing data set for future use. Some 1904 missing Db data points and 1612 corrected SOC HTC data points were added to the total of 4240 points in the 609 pedons that constitute the updated dataset. When O-layer thickness functions developed here were used, SOC and N stores were calculated for an additional 137 and 184 pedons respectively.