Temporal invasion regime attributes influence community synchrony and stability in an arid land system

Invasive species have become a major threat to ecosystems across the globe, causing significant ecological and economic damage. To anticipate how communities may respond to future invasions, it is crucial to refine how invader impacts are evaluated, especially in historically uninvaded and highly variable systems such as arid lands. While invader abundance is typically used to predict invader impacts, it may not effectively capture the dynamics that occur over time for established invaders that experience cyclical dynamics (i.e., boom-bust patterns), making it more challenging to track invader impacts. To address this issue, we leveraged a long-term vegetation dataset to develop a novel invasion regime framework for a dominant annual invader in North American deserts, Brassica tournefortii. Using abundance data over time, we evaluated how attributes of this invader's boom-bust dynamics (i.e., invasion level, boom frequency and magnitude) influence the long-term synchrony and stability of invaded Eolian sand dunes communities. We found that attributes that captured the temporal effects of the invader were strong indicators of the impacts of an invader on long-term attributes of communities. Specifically, the mean magnitude of invader booms led to a decrease in species asynchrony and community stability. Increasing boom frequency also decreased community stability, but this was more muted. Mean magnitude of invader booms also mediated shifts in the relationship between synchrony and stability, with this relationship becoming more shallow with increasing boom magnitudes. Our research emphasizes the significance of using community metrics that capture temporal dynamics to document invasion impacts within dynamic arid land systems. The invasion regime framework can additionally offer insights into the mechanisms that may enable the persistence of the invader over time. Together, this knowledge can be helpful in guiding decision-making and land management strategies aimed at effectively controlling and mitigating the impact of invasive species.