Invasive Plants May Change Soil Composition
USAgNet - 12/20/2012
The future landscape of the American Midwest could look a lot like
the past--covered in native grasslands rather than agricultural crops.
This is not a return to the past, however, but a future that could
depend on grasslands for biofuels, grazing systems, carbon
sequestration, and other ecosystem services. A major
threat to this ecosystem is an old one--weeds and their influence on the
soil.
According to a study in the journal Invasive Plant Science
and Management, when invasive plants spread, they can leave behind a
"legacy" of alteration in the native soil. Even after an invading
species has been controlled, its effects can inhibit the regrowth of
native plant species. The causes of this process are still
being investigated and may involve changes in soil food webs, soil
microbial communities, and mutualistic fungi.
In the study,
researchers tested soil conditions for changes in composition after
three growth cycles of invasive plant species. Researchers looked for
changes in colonization rates, diversity, and composition of
arbuscular-mycorrhizal fungi (AMF).
Three exotic plant
species--crested wheatgrass, smooth brome, and leafy spurge--were tested
in a glasshouse experiment. These plants, all characterized as strong
invaders, were grown in native soil collected from North Dakota
grasslands. Native species, including western wheatgrass, little
bluestem, and blue
gramma, were also grown, and after three growth cycles, soil composition
was compared among these treatments.
The findings of this study
showed that (1) invasive species changed the composition of AMF
communities in seedling roots of native grassland species, and (2)
invasive species were less colonized by AMF, forming fewer associations
than native grassland species. These findings suggest that the
ecological
differences in how these native and invasive plants interact with soil
may be a factor in this legacy effect.
While market and policy
demands might lead to a native grasslands agro-ecosystem, invasive
plants species could derail its establishment. Weed management must be a
component of any such ecosystem, so that it is possible to establish
grasslands that are useful and profitable.
Full text of the
article "Soil--Occupancy Effects of Invasive and Native Grassland Plant
Species on Composition and Diversity of Mycorrhizal AssociationsInvasive
Plant Science and Management, Vol. 5, No. 4, October-December 2012, is
available at www.wssajournals.org/
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