Diminishing returns from higher density restoration seedings suggest trade-offs in pollinator seed mixes

Published source details Wilkerson M.L., Ward K.L., Williams N.M., Ullmann K.S. & Young T.P. (2014) Diminishing returns from higher density restoration seedings suggest trade-offs in pollinator seed mixes. Restoration Ecology, 22, 782-789.
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This study is summarised as evidence for the following.

	Action	Category
	Other biodiversity: Plant flowers Action Link
	Pollination: Plant flowers Action Link

Other biodiversity: Plant flowers

A replicated study in 2008–2010 in farmland in the Central Valley, California, USA, found that a higher percentage of flower species persisted over time in flower plots that were planted with higher amounts of seed. Plants: Eight of nine species persisted for two years. Six species persisted for three years. Implementation options: Over the two years that followed planting, a higher percentage of species persisted in plots that were planted with two to four times as much seed (2x–4x) as the plots that were planted with the least seed (1x: 17–60%; 2x: 33–74%; 4x: 35–77%), but there was not a significant difference between the plots with 2x and 4x. The amount of seed planted had a significant effect on the percentage cover of plants, but it was not clear which treatments were significantly different from one another (data reported as log aggregate forb cover). Methods: Nine plots (1 x 8 m) were sown with the seeds of nine flower species in each of six hedgerows.
Pollination: Plant flowers

A replicated study in 2009–2011 in farmland in the Central Valley, California, USA, found more bees and bee species on one species of flowering plant than on five other species. Implementation options: Gum plant Grindelia camporum attracted more individuals and species of native bees than did five other species of flowering plants (190–220 vs 0–60 individuals; 10–11 vs 1–6 species). Methods: At each of three sites, five plots were planted with mixtures of native forbs in October 2009. Plots were 3 x 15 m. Bees on flowers were netted once/month (20 minutes/sample, April–September 2010–2011).