Biodiversity is often cited as a mediatory factor in grassland community resistance to precipitation changes with plant biomass or abundance as response variables. However, it is not well understood how biodiversity may impact physiological responses of individual species to different precipitation regimes. This study was conducted at the University of Kansas Field Station in a full factorial, paired block experiment that manipulates planted species richness (1, 2, 3 and 6 species), phylogenetic dispersion (under- and over-dispersed), and precipitation (50% and 150% ambient precipitation). The experiment includes 18 plant species, representative of tallgrass prairie communities, among 3 families (Fabaceae, Poaceae, and Asteraceae). Leaf level physiological traits were collected from late June to mid-August of 2022 on sunny days from 9h to 15h using a portable gas exchange system (model Li-COR 6800). Collected traits included assimilation (A), transpiration (E), stomatal conductance (gsw), intercellular CO2 (Ci), and water use efficiency (WUE). Measurements were taken on one plant per species in each of the diversity levels (monocultures, 2, and 3 species mixtures). Data was analyzed using linear mixed effect models in R with A, E, gsw, Ci, and WUE as response variables. Preliminary results of the linear mixed effect models suggest that species identity is highly significant in respect to A, E, gsw, Ci, and WUE (p < 0.001 for each of the factors). As expected, the 50% precipitation treatment had greater WUE than the 150% precipitation treatment (p < 0.05). Although WUE decreased with species richness overall, WUE of individual species varied substantially with species richness (p < 0.05). Of the 15 species measured, 5 species showed a positive WUE trend with increasing species richness, 8 species showed a negative trend with increasing diversity, and 2 species showed no pattern. Interestingly, only the species showing negative WUE with increasing diversity included statistically significant (0.05 < p < 0.001, varied among species) or marginally nonsignificant patterns (0.1 < p < 0.05). A, E, gsw, and Ci results are expected July 2023. As precipitation patterns change, it is critical to understand how individual species may differentially respond to altered precipitation regimes and how the presence of other species can alleviate water stress. These data may help inform grassland conservation and restoration efforts of particularly sensitive species and what ecophysiological traits are important for monitoring plant health and, subsequently, community persistence in a changing climate.
