Compost may encourage native grasses and discourage forbs

Abstract

Farmers and land managers have used compost as a beneficial amendment to improve soil health and increase plant yield for centuries. This study analyzes the effects of compost on native plant establishment in the presence of a non-native species, Bromus inermis (smooth brome). In a replicated greenhouse study, I applied four compost treatments to pots containing native plant species and smooth brome: a control group with no compost added, and three other treatments in which compost was added at 10%, 20%, and 30% by volume. After 7 weeks of growth, I compared the dry weight of the aboveground biomass and the abundance of each species across treatments. As the compost increased, 4 grass species reacted positively and increased in biomass. However, forb species did not follow this trend, and their biomass decreased as the compost levels increased.