Experimental reintroduction of three grassland forbs to assess climate-adjusted provenancing, grazing protection and weed control

Abstract

We explored climate-adjusted provenancing as a strategy for reintroduction of three perennial forbs: Microseris walteri, Bulbine bulbosa and Stackhousia monogyna into native grassland with a history of livestock grazing. Seed source populations were sampled over a temperature gradient of 2°C, located up to 120km from the receiving site. Two receiving-site management treatments were applied: hand removal of exotic species, and exclusion of macropod grazing and trampling. There were no effects of weeding the receiving grassland and we concluded the low fertility of the site provided protection from exotic competition. After eight growing seasons, protection from grazing resulted in double to triple the numbers of established plants, depending on the species. Amongst populations within a species, larger seeds and early emergence reflected later establishment success for Bulbine only. At the species level, early performance was not indicative of later numbers of reproductive plants established. We found no long-term evidence of home-site advantage in any species, and no apparent disadvantage of non-matching lithology. All source populations were represented at the end of the experiment (Season 6). Counts after eight seasons’ growth indicated a continuing trend of population increase in all three species. The persistence of all populations suggests that admixture or climate-adjusted provenancing may be a realistic option to restore depleted populations of herbaceous plants in grassy eucalypt woodlands in a warming climate.