The impact of two non-native plant species on native flora performance: potential implications for habitat restoration

Both Impatiens glandulifera and Fallopia
japonica are highly invasive plant species that have
detrimental impacts on native biodiversity in areas
where they invade and form dense monocultures. Both
species are weakly dependent on arbuscular mycorrhizal
fungi (AMF) for their growth and, therefore,
under monotypic stands, the AMF network can
become depauperate. We evaluated the impact of
I. glandulifera and F. japonica on the performance
(expressed as shoot biomass) of three UK native
species (Plantago lanceolata, Lotus corniculatus and
Trifolium pratense) grown in soil collected from under
stands of both invasive plants and compared to plants
grown in soil from under stands of the corresponding
native vegetation. All native species had a higher
percentage colonisation of AMF when grown in
uninvaded soil compared to the corresponding invaded
soil. P. lanceolata and L. corniculatus had a higher
biomass when grown in uninvaded soil compared to
corresponding invaded soil indicating an indirect
impact from the non-native species. However, for
T. pratense there was no difference in biomass between
soil types related to I. glandulifera, suggesting that the
species is more reliant on rhizobial bacteria. We
conclude that simply managing invasive populations
of non-native species that are weakly, or non-dependent,
on AMF is inadequate for habitat restoration as
native plant colonisation and establishment may be
hindered by the depleted levels of AMF in the soil
below invaded monocultures. We suggest that the
reintroduction of native plants to promote AMF
proliferation should be incorporated into future management
plans for habitats degraded by non-native
plant species