PS 15-210 - Lineage-based differences in photosynthetic and hydraulic properties of grasses in North America

Abstract: Grass-dominated ecosystems represent up to 40% of the terrestrial biosphere, and grasses further comprise much of the herbaceous layer in many other systems. Grasses exhibit trait variation across these systems, but represent a small proportion of global trait databases and are not uniquely represented in earth system models. We are investigating lineage-based trait coordination and distribution along environmental gradients in North America at select NEON and LTER to examine whether, within a given environment, traits converge across lineages or if lineage-specific traits remain relatively static across different environments.

We performed A/Ci curves and measured turgor-loss point and leaf hydraulic conductance at five grassland sites within the US. These sites— Konza, Woodworth, CPER, Jornada and Cedar Creek— vary greatly by temperature, precipitation and species composition. There was a general representation of grass subfamilies across sites, but each site tended to be dominated by a subfamily, for example Chloridiodeae at the short-grass CPER site and Panicoideae and the tall-grass Konza site. Across sites, Amax, Kleaf and turgor loss point were significantly different (linear mixed model) by grass subfamily. Amax was 24.5 ± 2.8 for Aristidoideae, 27.2 ±1.5 for Chloridoideae, 25.3 ± 1.5 for Panicoideae and 13.3 ± 0.8 for Pooideae, all values are mmol m^-2 s^-1. Kleaf was 23.0 ± 8.7 Aristidoideae, 6.8 ± 1.2 for Chloridoideae, 3.2 ± 0.44 for Panicoideae and 5.3 ± 1.5 for Pooideae, all values are mmol m^-2 s^-1 MPa^-1. Turgor loss points were -2.1 ± 0.07 for Aristidoideae, -1.7 ± 0.06 for Arundinoideae, -2.1 ± 0.03 for Chloridoideae, -1.6 ±0.02 for Panicoideae and -2.0 ±0.03 for Pooideae, all values are MPa. For species that were found at multiple sites, there were significant differences in hydraulic properties, but not Amax.