Kourtev, P.S. and Ehrenfeld, J.G. and
Häggblom, M. (2003). Experimental analysis of the
effect of exotic and native plant species on the structure and
function of soil microbial communities. Soil Biol. &
Biochem., 35: 895-905.
Invasions of exotic plant species are among the most pervasive and
important threats to natural ecosystems, however, the effects of
plant invasions on soil processes and the soil biota have rarely
been investigated. We grew two exotic and a native under-story
plant species in the same mineral soil from a non-invaded forest
stand in order to test whether observed differences in the field
could be experimentally produced in the greenhouse. We
characterized changes in the soil microbial community structure
(as indexed by PLFAs) and function (as indexed by enzyme
activities and SIR), as well as changes in potential nitrogen
mineralization rates. We found that the invasion of two very
dissimilar exotic species into the under-story of deciduous
forests in eastern North America can rapidly cause changes in most
of the studied soil properties. At the end of the three-month
incubation, soils under the exotic species had significantly
different PLFA, enzyme and SIR profiles than both initial soils
and soils where native shrubs had been grown. We also observed a
significant increase in pH and nitrification rates under one of
the exotic plants. Such changes in the soil are potentially
long-term (e.g. changes in soil pH) and are therefore likely to
promote the re-invasion of these and other exotics. Both
management of exotic plant invasions and the restoration of native
communities must take into account exotic species effects on the
soil.
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