Revegetation Strategies for Ecological Restoration

Abstract

Seed-based revegetation is often unsuccessful in ecological restoration efforts in drylands, mainly due to an unfavorable environment for germination and establishment, as well as poorly understood germination behaviors of restoration-relevant plant species. We conducted two experiments in order to first identify potential revegetation methods for enhancing emergence and establish through the use of seed balls, and then to identify specific germination behaviors of a pollinator restoration plant known as milkweed (plants belonging to the genus Asclepias). In our seedball field experiment, we tested different seed ball types by observing how altering seedball shapes and additives impacted emergence and establishment. We found that overall, seedballs significantly enhanced early emergence, but had no long term beneficial effects on establishment, with no significant differences between the seedball types. We then conducted a germination study of various milkweed species sourced from different regions throughout the U.S. to detect differences in germination behaivour in response to warm incubation temperatures and cold stratification. Overall we found that dormant milkweed populations responded postively to a six week period of cold stratification, but that two southern populations of A. asperula and A.syriaca may have higher sensitivty to warm incubation temperature. We also found that non dormant milkweeds displayed similar germinaiton rates across a range of warm incubation temperatures, but that one populuation of A. incarnata may have higher sensitivty to warm incubation temperature while two populations of A. angustifiulia and A. speciosa have a stronger preference for warmer incubation temperatures. We suspect these differences in germinaiton behavior are linked to last frost date and precipitation seasonality of the source climate.