Invasive-dominated grasslands in Hawai'i are resilient to disturbance

Area of Science:

• Ecology
• Restoration Ecology
• Plant Community Dynamics

Background:

• Non-native plant invasions and increasing disturbance reshape landscapes globally.
• Predicting plant community assembly after disturbance is challenging, especially in invaded ecosystems.
• Understanding these dynamics is crucial for managing anthropogenically impacted areas like Hawai'i's dryland, grazed landscapes.

Purpose of the Study:

• To investigate how mechanical disturbance affects plant community assembly in invaded Hawaiian habitats.
• To determine the role of dominant vegetation types and resident species in post-disturbance recovery.
• To assess the resilience of invaded grasslands and the potential for native species re-establishment.

Main Methods:

• Mechanically disturbed 100 m² plots in six invaded vegetation types (invasive grasses, native shrub, native bunchgrass).
• Monitored woody plant colonization and herbaceous cover for 21 months post-disturbance.
• Categorized species roles (competitor, colonizer) and assessed survival of planted native species.

Main Results:

• Dominant vegetation types exhibited varied post-disturbance syndromes, with both inter- and intra-specific variation in colonizer vs. competitor roles.
• Native shrub seedlings did not survive long-term in invaded habitats, likely due to competitive regrowth of invasive grasses.
• Survival of planted native species was negatively correlated with the regrowth rate of dominant resident species.

Conclusions:

• Hawai'i's post-agricultural, invaded grasslands represent stable states, demonstrating high resilience to disturbance.
• Resident plant communities significantly influence species interactions and seed availability, shaping community responses to disturbance.
• Management strategies should consider the strong influence of resident species in maintaining invaded ecosystem stability.