Jd. Jastrow et al., CONTRIBUTIONS OF INTERACTING BIOLOGICAL MECHANISMS TO SOIL AGGREGATE STABILIZATION IN RESTORED PRAIRIE, Soil biology & biochemistry, 30(7), 1998, pp. 905-916
A better understanding of the soil aggregation process is needed to ad
dress a variety of concerns, including soil quality and erosion, agric
ultural sustainability, soil C sequestration, the mobility of hazardou
s chemicals and remediation of contaminated sites. We used data from a
chronosequence of tallgrass prairie restorations and a path analysis
approach to evaluate how the lengths of two dia size classes of fibrou
s roots, the length of external mycorrhizal hyphae, microbial biomass
C, hut-water soluble carbohydrate C and soil organic C interact to pro
mote the stabilization of soil aggregates. The measured binding agents
accounted for 88% of the variation in macroaggregates >212 mu m diame
ter and goodness-of-fit indexes indicated a good practical fit of the
path model to the data. The restoration of macroaggregate structure in
this system was apparently driven by the direct and indirect effects
of roots and external hyphae, with lesser relative contributions by th
e three measured C pools. Although the two root size classes had simil
ar direct effects on the percentage of macroaggregates, their indirect
contributions differed substantially. Fine roots (0.2-1 mm diameter)
exerted considerable indirect effects via their strong influences on e
xternal hyphae and microbial biomass C. Very fine roots ( < O.2 mm dia
) made a stronger contribution to soil organic C than fine roots, but
their overall indirect contribution to aggregation was minimal. In add
ition, the relative importance of each binding agent varied for differ
ent size fractions of macroaggregates and generally supported the hypo
thesis that the effectiveness of various binding mechanisms depends oi
l the physical dimensions of the binding agents relative to the spatia
l scales of the aggregate planes of weakness being bridged. Published
by Elsevier Science Ltd.