Effects of Precipitation Changes on Switchgrass Biomass and Greenhouse Gas Emission

Climate change and the energy crisis are two important issues we face in the world today. Bioenergy crops such as switchgrass could be very useful in solving these problems. But the interaction between switchgrass productivity and climate change, for example, precipitation changes, has not been well investigated. For this reason, we conducted a field precipitation experiment in Nashville, Tennessee, to study the effects of precipitation on switchgrass growth and soil respiration. Precipitation treatments included five levels: a control (ambient precipitation), +33%, +50% of ambient to simulate wet, and –33% and –50% of ambient to simulate drought treatments. We measured switchgrass physiology, roots, biomass, and soil respiration. Results showed that photosynthetic rates of switchgrass in the +33% and +50% treatments were about 19.5 µmol CO2 m–2s –1, significantly higher than that in the other three treatments. The lowest one was found in the –50% treatment (17.26 µmol CO 2 m–2 s–1). The biomass in the +50% treatment was the highest and the lowest was observed in the –50% treatment. The results indicate that, although switchgrass is a drought tolerant grass, high precipitation stimulates switchgrass photosynthesis and growth