|Yu, Chih-li - Tennessee State University|
|Hui, Dafeng - Tennessee State University|
|Deng, Qi - Tennessee State University|
|Dzantor, E - Tennessee State University|
|Shen, Weijun - Chinese Academy Of Sciences|
|Luo, Yiqi - University Of Oklahoma|
Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/4/2017
Publication Date: 8/17/2017
Citation: Yu, C., Hui, D., Deng, Q., Dzantor, E.K., Fay, P.A., Shen, W., Luo, Y. 2017. Responses of switchgrass soil respiration and its components to precipitation gradient in a mescocosm study. Plant and Soil. 420:105-117. https://doi.org/10.1007/s11104-017-3370-2.
Interpretive Summary: The rate at which carbon leaves the soil as carbon dioxide (CO2), termed ‘soil respiration’, indicates the rate of carbon (C) loss from soil back to the atmosphere, and is a critical link between carbon in natural and managed ecosystems and in the atmosphere. Soil respiration combines CO2 losses from two sources – plant roots, and soil microorganisms decomposing carbon stored in the soil. Thus, soil respiration affects the amount of carbon remaining in soil, termed carbon sequestration. Root and microbial CO2 losses are known generally to increase in wetter, warmer soils. Anticipated climate warming and more variable rainfall raise questions about the potential for agroecosystems to sequester carbon in future climates, and few studies have examined soil respiration in switchgrass, a promising bioenergy crop. In this study, switchgrass plants in pots in a greenhouse were subjected to wet or dry precipitation treatments over two growing seasons, and soil respiration was partitioned into its root and microbial contributions. Importantly, switchgrass plants were grown in pots large enough to provide a realistic rooting volume, and allowed soil moisture and soil physical properties to be precisely controlled. Soil respiration rates were higher in plants in wetter treatments, where soil respiration also increased more with growing season increases in temperature compared to plants in drier treatments. Changes in soil microbial respiration with precipitation explained most of the soil respiration increases in wetter treatments. If these results translate from the greenhouse to the field, they suggest that if climate warming is accompanied by increased precipitation, losses of CO2 from soils might be greater than expected, decreasing the potential soil carbon storage in switchgrass agroecosystems.
Technical Abstract: The objectives of this study were to investigate the effects of the precipitation changes on soil, microbial and root respirations of switchgrass soils, and the relationships between soil respiration and plant growth, soil moisture and temperature. A mesocosm experiment was conducted with five precipitation treatments over two years in a greenhouse in Nashville, Tennessee. The treatments included ambient precipitation, - 50%, -33%, +33% and +50% of ambient precipitation. Soil, microbial, and root respirations were quantified during the growing seasons. Mean soil and root respirations in the +50% treatment were the highest (2.48, and 0.93 umol CO2 m-2s-1, respectively) among all treatments. Soil microbial respiration contributed more to soil respiration, and had higher precipitation sensitivity mostly than root respiration. Increases in precipitation mostly enhanced microbial respiration while decreases in precipitation reduced both microbial and root respirations. Across precipitation treatments, soil respiration was significantly influenced by soil moisture, soil temperature, and aboveground biomass. Our results showed that microbial respiration was more sensitive to precipitation changes, and precipitation regulated the response of soil respiration to soil temperature. The information generated in this study will be useful for model simulation of soil respiration in switchgrass fields under precipitation changes.