Effects of management and pore characteristics on organic matter composition of macroaggregates: evidence from characterization of organic matter and imaging: Pore characteristics and OM composition of macroaggregates
- Department of Plant, Soil and Microbial Sciences, Michigan State University, 1066 Bogue St., East Lansing MI 48823 USA
- Department of Chemistry and Biochemistry, Old Dominion University, 4541 Hampton Blvd, Norfolk VA 23529 USA
- Center for Advanced Radiation Sources, Argonne National Laboratory, The University of Chicago, 9700 South Cass Ave., Argonne IL 60439 USA
Macroaggregates are of interest because of their fast response to land management and their role in the loss or restoration of soil organic carbon (SOC). The study included two experiments. In Experiment I, we investigated the effect of long-term (27 years) land management on the chemical composition of organic matter (OM) of macroaggregates. Macroaggregates were sampled from topsoil under conventional cropping, cover cropping and natural succession systems. The OM of macroaggregates from conventional cropping was more decomposed than that of cover cropping and especially natural succession, based on larger δ15N values and decomposition indices determined by multiple magic-angle spinning nuclear magnetic resonance (13C CP/MAS NMR) and Fourier transform infrared (FTIR) spectroscopy. Previous research at the sites studied suggested that this was mainly because of reduced diversity and activity of the decomposer community, change in nutrient stoichiometry from fertilization and contrasting formation pathways of macroaggregates in conventional cropping compared with cover cropping and, specifically, natural succession. In Experiment II, we investigated the relation between OM composition and pore characteristics of macroaggregates. Macroaggregates from the natural succession system only were studied. We determined 3-D pore-size distribution of macroaggregates with X-ray microtomography, for which we cut the macroaggregates into sections that had contrasting dominant pore sizes. Then, we characterized the OM of macroaggregate sections with FTIR and δ15N methods. The results showed that within a macroaggregate, the OM was less decomposed in areas where the small (13–32 µm) or large (136–260 µm) pores were abundant. This was attributed to the role of large pores in supplying fresh OM and small pores in the effective protection of OM in macroaggregates. Previous research at the site studied had shown increased abundance of large and small intra-aggregate pores following adoption of less intensive management systems. It appears that land management can alter the OM composition of macroaggregates, partly by the regulation of OM turnover at the intra-aggregate scale.
- Research Organization:
- Argonne National Laboratory (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
- Sponsoring Organization:
- USDOE; National Science Foundation (NSF)
- OSTI ID:
- 1355029
- Journal Information:
- European Journal of Soil Science, Vol. 68, Issue 2; ISSN 1351-0754
- Country of Publication:
- United States
- Language:
- ENGLISH
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