Interannual Variations of Switchgrass Physiology, Growth, and Soil Respiration under Precipitation Changes: Comparisons between Greenhouse and Field Experiments

Background/Question/Methods

Plant ecophysiology, biomass, and yield are often influenced by climatic factors such as precipitation. But the interannual variations of switchgrass photosynthesis, biomass, and soil respiration has not been well investigated, particularly under different precipitation changes. We have conducted two long-term precipitation experiments with switchgrass Alamo under precipitation changes in greenhouse and field. The experiments used a randomized block design with 5 precipitation treatment levels (-50%, -33%, ambient, +33%, and +50% of ambient precipitation). Five blocks were used for the greenhouse experiment and four blocks were used for the field study. We measured switchgrass leaf physiology (photosynthesis, stomatal conductance, transpiration and water use efficiency), biomass, and soil respiration over six years.

Results/Conclusions

The results showed that there were strong interannual variations of these variables for both greenhouse and field experiments, but larger variations were found in the field plots. Precipitation treatment significantly influenced leaf photosynthesis, biomass, and soil respiration. There were positive linear relationships of leaf photosynthesis, transpiration, biomass, and soil respiration with precipitation in the greenhouse pots, but only leaf photosynthesis and transpiration linearly increased with precipitation in the field plots. While strong interannual variations were found for both greenhouse and field experiments, different mechanisms might be involved. Our results also revealed that we need to be cautious when extrapolating results in greenhouse to field conditions.