Improving our understanding of the ecological controls on the distribution and phenology of C3 and C4 grasses in response to climate variations

• Stephanie Pau

Abstract
This proposed project seeks to analyze and synthesize herbarium, climate, and satellite data over several decades to address the spatial and temporal response of C3 and C4 grasses to climate variability in the Hawaiian Islands. Complicating our understanding of C3 and C4 response to climate change and increased CO2 are large uncertainties regarding their differential response to climate variability. Numerous studies have demonstrated ecological sorting of C3 and C4 grasses along static spatial climate gradients, though few studies have focused on phenological differences between C3 and C4 grasses. In Hawaii, C4 grasses initiate a grass-fire feedback cycle that directly affects ecosystem structure and function. El Niño-driven droughts, the greatest source of interannual climate variability in Hawaii, may contribute to this feedback by providing a “tipping point” for C4 grass invasion into new regions. Results from this project will provide new information on the functional significance of C4 photosynthesis and the invasion dynamics of C4 grasses. This work will also provide insight on the response of these grasses to climate variability, and lay the groundwork for merging herbarium datasets with satellite data to create an ecological informatics database for grasses.