Discipline: Biological Sciences
Katherine Miller - Tennessee State University
Co-Author(s): Dafeng Hui, Tennessee State University, Nashville, TN; Qi Deng, Tennessee State University, Nashville, TN; and Chih-Li Yu, Tennessee State University, Nashville, TN
The quantification of ecosystem productivity in response to climate change has been heavily investigated. However, it remains unclear how grassland ecosystem productivity specifically responds to precipitation changes. A degree of controversy exists in the literature as to whether the relationship is linear or nonlinear and asymmetric or symmetric. We conducted two experiments to investigate ecosystem productivity and soil CO2 emission responses to precipitation changes in switchgrass, Panicum virgatum. The first experiment was a mesocosm (big pot) study in a greenhouse. The second experiment was performed in the field. Both experiments used a randomized complete block design with 5 precipitation treatment levels (-50%, -33%, ambient, +33%, and +50%). We used a timer-controlled irrigation system to implement the precipitation treatments in the mesocosm study. The ambient treatment was based on 50 years of historic precipitation data. The field experiment was designed using a rainfall-interception-redistribution system. We hypothesize that switchgrass’ relationship to precipitation changes exhibit nonlinear and asymmetric responses. The measured variables included: environmental conditions (air temperature, soil temperature, and soil moisture), plant physiology and growth (leaf photosynthesis, transpiration, phenology, height and tiller, and biomass/carbon allocation), and greenhouse gas emission (soil respiration). The results demonstrated consistent changes, though there was variation between the field and greenhouse experiments. Precipitation changes highly influenced the physiology, growth, and soil respiration of switchgrass. The responses of aboveground net primary production (ANPP) were indeed nonlinear and asymmetric. Yet, the responses of soil respiration to precipitation were close to symmetric and linear. Future research should focus on further testing of the double asymmetry model with more precipitation levels and longer time frames.
Funder Acknowledgement(s): Funding was provided by the USDA-Capacity Building grant (2013-38821-21390), Evans-Allen grant, and NSF grants (1504886,1623085).
Faculty Advisor: Dafeng Hui, Katherinenicolemiller@gmail.com
Role: I measured photosynthesis, transpiration, respiration (soil and leaf), and biomass for this study. I also monitored the environmental conditions. Additionally, I aided in the basic maintenance of the greenhouse and field.