Forb species establishment increases with decreased grass seeding density and increased forb seeding density in an experimental prairie restoration, northeast Kansas, USA

  • Published source details Dickson T.L. & Busby W.H. (2009) Forb species establishment increases with decreased grass seeding density and with increased forb seeding density in a northeast Kansas, U.S.A., experimental prairie restoration. Restoration Ecology, 17, 597-605


Most prairie restorations have lower plant diversity than natural prairies. This may be due to inhibition of forb establishment by dominant grasses and/or to the often low seeding densities of forbs used in restorations. This study investigated the effect of sowing various densities of forb and warm-season grasses into a prairie restoration in northeast Kansas (95°08′W, 38°49′N; central USA) to assess the effect on forb establishment.

A field surrounding the experimental area in the ‘Conservation Reserve Program’ (CRP) was sown with native species in May 2001. A few days later (21 May), the experimental area was sown at five combinations of forb and grass seed densities relative to those in the CRP. Seeds were hand-broadcast and raked into the bare soil.

Each seeding densities was replicated six times (2 x 2 m plots) in a randomized complete block design. Plant species cover was estimated (within a 1 m² quadrat/plot) in May/June and August/September (2001-2004). Aboveground biomass samples were harvested in mid-August 2004, dried and weighed.

From 2002 to 2004, average sown grass cover was 2% in the no-grass-sown treatment, whilst increasing from 26 to 70% in grass-sown treatments. Increasing forb sowing density led to a small but significant decrease in sown grass cover only in 2003. In 2004, grass biomass was similar between grass-sown treatments; only in the no-grass-sown treatment were their cover and biomass significantly lower (all years).
Four years after seeding, higher densities of grass seeds decreased forb cover, biomass and species richness; higher densities of forb seeds increased forb richness. Results suggest that dominant grasses outcompete many native forbs and that seed availability limits establishment of some. Forb diversity can be increased by decreasing grass seeding density and/or by increasing forb seeding density. As increasing forb seeding density across a large area may be prohibitively expensive, a low seeding density of grasses is recommended.
Note: If using or referring to this published study, please read and quote the original paper, this can be viewed at:

Output references

What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, terrestrial mammals, forests, peatland and control of freshwater invasive species. More are in progress.

More about What Works in Conservation

Download free PDF or purchase
The Conservation Evidence Journal

The Conservation Evidence Journal

An online, free to publish in, open-access journal publishing results from research and projects that test the effectiveness of conservation actions.

Read the latest volume: Volume 18

Go to the CE Journal

Subscribe to our newsletter

Please add your details if you are interested in receiving updates from the Conservation Evidence team about new papers, synopses and opportunities.

Who uses Conservation Evidence?

Meet some of the evidence champions

Endangered Landscape Programme Red List Champion - Arc Kent Wildlife Trust The Rufford Foundation Save the Frogs - Ghana Bern wood Supporting Conservation Leaders National Biodiversity Network Sustainability Dashboard Frog Life The international journey of Conservation - Oryx British trust for ornithology Cool Farm Alliance UNEP AWFA Butterfly Conservation People trust for endangered species Vincet Wildlife Trust