Persistent asymmetrical priority effects in a California grassland restoration experiment

Area of Science:

• Ecology
• Community Ecology
• Plant Ecology

Background:

• The sequence of species introduction significantly influences ecological community assembly.
• Priority effects, where early-arriving species impact later ones, are known drivers of community structure.
• The long-term persistence and duration of these priority effects remain incompletely understood.

Purpose of the Study:

• To investigate the long-term persistence of priority effects in a plant community assembly experiment.
• To determine how the order of arrival for grasses and forbs influences community development over 6-8 years.
• To assess the potential of manipulating community assembly trajectories through seeding priority for ecological restoration.

Main Methods:

• A community assembly experiment was established using native grasses and forbs.
• Treatments included monocultures of grasses or forbs, mixed plantings, and staggered plantings with one-year priority for either grasses or forbs.
• Community composition and species cover were monitored over 6-8 years post-planting.

Main Results:

• Initial priority effects benefited both grasses and forbs.
• After 6-8 years, the impact of priority treatments was variable: some species persisted only with priority, others maintained high cover, some lost the priority effect signature, and some went extinct.
• Grass priority over forbs demonstrated strong and lasting effects, whereas forb priority over grasses was less persistent.
• Distinct community compositions emerged based on the priority treatments.

Conclusions:

• Temporal priority can confer long-term advantages for certain species, persisting for at least 8 years.
• The differential persistence of priority effects leads to varied long-term community compositions.
• Strategic manipulation of species arrival order via seeding priority shows promise as a restoration tool.