The literature was reviewed and analyzed to determine the feasibility of using a combination of add hydrolysis and CO 2 -C release during long-term incubation to determine soil organic carbon (SOC) pool sizes and mean residence times (MRTs). Analysis of 1100 data points showed the SOC remaining after hydrolysis with 6 M HCI ranged from 30 to 80% of the total SOC depending on soil type, depth, texture, and management. Nonhydrolyzable carbon (NHC) in conventional till soils represented 48% of SOC; no-till averaged 56%, forest 55%, and grassland 56%. Carbon dates showed an average of 1200 yr greater MRT for the NHC fraction than total SOC. Long-term incubation, involving measurement of CO 2 evolution and curve fitting, measured active and slow pools. Active-pool C comprised 2 to 8% of the SOC with MRTs of days to months; the slow pool comprised 45 to 65% of the SOC and had MRTs of 10 to 80 yr. Comparison of field 14 C and 13 C data with hydrolysis-incubation data showed a high correlation between independent techniques across soil types and experiments. There were large differences in MRTs depending on the length of the experiment. Insertion of hydrolysis-incubation derived estimates of active (C a ), slow (C s ), and resistant pools (C r ) into the DAYCENT model provided estimates of daily field CO 2 evolution rates. These were well correlated with field CO 2 measurements. Although not without some interpretation problems, acid hydrolysis-laboratory incubation is useful for determining SOC pools and fluxes especially when used in combination with associated measurements.
ABSTRACT
PUBLICATION RECORD
- Publication year
2006
- Venue
Soil Science Society of America Journal
- Publication date
2006-05-01
- Fields of study
Chemistry, Environmental Science
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