Soil Organic Matter Dynamics - The Ecology of Agricultural Landscapes - page 121

Figure 5.6 . Fourier transformed mid-infrared spectra of KBS soil, including the whole soil
and its various fractions. Absorbance bands of different organic functional groups are shown
as vertical bars. From F. Calderón (unpublished data).
differentiation among SOM fractions for all four soils (Fig. 5.7), despite differ-
ent MRTs across these sites (Table 5.2). The interaggregate fraction was well sep-
arated from all others, while the intraaggregate and silt fractions were grouped
together. The clays clearly separated from other fractions, and the clay fraction in
the prairie-derived SOM from Lamberton separated from the forest-derived clays
of KBS, Wooster, and Hoytville. Haile-Mariam et al. (2008) used δ 13 C to determine
the MRT of the SOM fractions of the Hoytville and Lamberton soils. Their analysis
showed that the inter- and intraaggregate C 3 -derived SOC (i.e., noncorn SOC) of the
KBS soil was the youngest, which is consistent with the 14 C dating data (Table 5.2).
The KBS soil also had higher SOM turnover rates than the other soils examined, as
determined by incubation, carbon dating, and 13 C field analysis (Collins et al. 1999,
2000; Paul et al. 2001a). These regional comparisons offer a powerful means for
identifying general controls on SOM dynamics in larger landscapes (Fierer et al.
2009, Morris et al. 2010).