Toward a comprehensive understanding of the phenological responses of non-native plants to climate warming: a review.

backgroundPlants often shift their phenology in response to climate warming, with potentially important ecological consequences. Relative differences in the abilities of native and non-native plants to track warming temperatures by adjusting their phenologies could have cascading consequences for ecosystems. Our general understanding of non-native species leads us to believe these species may be more phenologically sensitive than native species, but evidence for this has been mixed, likely due, in part, to the myriad of diverse ecological contexts in which non-natives have been studied. SCOPE: Here, we review the current state of knowledge on non-native plant phenological responses to climate warming. From observational and experimental studies, we synthesize: (1) the ways in which non-native plant phenology shifts with increased temperature, (2) the relative differences between natives and non-natives in phenological timing and sensitivity to warming, (3) the contingencies driving variable non-native phenological responses to warming, and (4) the ecological consequences of warming-induced phenological shifts in non-natives.

conclusionsEarly-season phenophases tend to advance with warming, sometimes (but not always) more so in non-native species relative to native species. Late-season phenophases, on the other hand, tend to be more variable: advancing, delaying, or remaining unchanged. Similarly, relative differences in phenological sensitivity between native and non-native plants were less consistent for late-season phenophases. However, our ability for inference is limited by the scope of studies done to date, which best represent temperate ecosystems in the Northern Hemisphere. We found phenological shifts in non-native species to be driven by various factors, including their evolutionary histories and the environmental context of the invaded system. Shifts in non-native phenologies result in varied ecological consequences, from shifting demographics of the non-native species themselves to changes in ecosystem level processes such as carbon cycling. Additional study addressing key gaps is vital to improving understanding of non-native phenological responses to warming.