Differences in phenology between non-native C4 grasses and native C3 and C4 grasses in a seasonally dry ecosystem

Abstract

Plant species phenology is an important driver of invasions in seasonal climates. The phenology of non-natives is generally uncoupled from that of native species. Grasses cover a large proportion of the land surface and are important invaders around the world. Interestingly, the phenology of native and non-native grasses could be modulated by the different metabolic pathways. We aimed to compare the vegetative and reproductive phenology of invasive C₄ grasses with that of coexisting native C₃ and C₄ grasses and to explore the relationship between phenology and climate. We recorded the onset, duration and synchronicity of vegetative and reproductive phenology (flowering and fruiting) during 1 year. Native C₃ grasses had 50% of their above-ground biomass green earlier and remained in that state for a longer period than non-native and native C₄ grasses. Flowering and fruiting occurred earlier in non-native C₄ grasses than in native C₄ grasses. The flowering period was longer in non-native C₄ than in native C₃ and C₄, with the non-native Melinis repens (Poaceae), a highly invasive species worldwide, accounting for most of the difference. Non-native C₄ tended to exhibit a lower flowering and fruiting synchrony than both native C₃ and C₄ species. Finally, reproductive and vegetative phenology was positively associated with temperature, while precipitation was mostly associated with C₄ species. The uncoupled vegetative phenology observed could be related to differences in metabolism among the studied species, while the uncoupled reproduction between non-native and native C₄ grasses could be due to an advantage in resource use by non-native species. Our work provides the first insight into the possible role of the species origin and metabolic pathways in the vegetative and reproductive phenology of invasive non-native C₄ and native C₃ and C₄ grasses. Finally, we suggest future directions to elucidate these processes.