Data from: The effects of native seed mix composition and sowing density on plant community reassembly in wetlands

Seed-based restoration of wetlands is often necessary to improve important
ecosystem functions (e.g., invasion resistance, habitat-provisioning) and
meet society’s need for wetland ecosystem services such as supporting
recreational activities and improving water quality.  However,
persistent questions remain about the composition and sowing density of
seed mixes needed to restore robust native wetland plant
communities.  In Great Salt Lake wetlands (Utah, USA), the
revegetation of native species is crucial to recovering critical habitat
and preventing reinvasion of the invasive, non-native grass, Phragmites
australis and other invasive species (e.g., Typha spp.).  In
greenhouse and field experiments, we investigated the effects of seed mix
composition and sowing density on plant community reassembly.  We
predicted that seed mixes containing native forb species with
resource-preempting traits (e.g., rapid seedling emergence, high
aboveground growth rate), and high sowing densities (>5,500 pure
live seed m-2), would increase native plant light acquisition and
establishment, thereby limiting invasive species.  To our
surprise, the effect of seed mix composition on native plant performance
(cover, biomass) varied among our experiments, with distinct differences
between plant functional groups arising.  Native forb species had
the highest performance in the greenhouse, but native grasses performed
better in the field.  Although multiple seed mix compositions
show promise for establishing high native cover and biomass, these mixes
may not always suppress invasive species.  Interestingly, seed
mix composition most often affected plant performance independent of
sowing density.  However, in one greenhouse experiment, we found
that only slow-growing mixes required a high sowing density to maximize
native cover, an indication that the ideal sowing density may depend on
the seed mix composition.  Our research also supports the idea
that in addition to reducing propagules of invasive species via
appropriate management strategies, the application of higher sowing
densities (>5,500 pure live seed m-2) may lead to more favorable
outcomes when a high density of invasive plant seeds remains or stressful
field conditions are present.  This research contributes to our
knowledge of plant community reestablishment in wetlands and demonstrates
how seed-based restoration strategies can catalyze native species
revegetation and in some situations, reduce the cover of invasive species.