Effects of Precipitation Treatments on Switchgrass Chlorophyll Content, Photosynthesis, Biomass, and Yield

Plant ecophysiology, biomass, and yield are often influenced by climatic factors such as precipitation. But how switchgrass leaf chlorophyll content, photosynthesis, biomass, and yield are influenced by precipitation has not been well investigated. We have conducted a field precipitation experiment with switchgrass since 2013. The experiment used a randomized block design with 5 precipitation treatment levels (-50%, -33%, ambient, +33%, and +50% of ambient precipitation) and 5 blocks. We measured switchgrass leaf physiology and biomass over years, soil respiration, and also chlorophyll content and yield since 2018. The results showed that precipitation treatment significantly influenced leaf photosynthesis, biomass, and soil respiration, but had limited influences on leaf chlorophyll content and yield. Strong interannual variations were found for photosynthesis, biomass, and soil respiration. Biomass showed a nonlinear and asymmetric response to precipitation change and soil respiration had a symmetric response to precipitation change. Our results indicated that switchgrass is a drought tolerant grass, but extreme precipitation changes can significantly influence switchgrass growth and soil respiration.