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ARS Home » Plains Area » Temple, Texas » Grassland Soil and Water Research Laboratory » Research » Publications at this Location » Publication #304635
Title: Genotype and plant trait effects on soil CO2 efflux responses to altered precipitation in switchgrass

Author
item KHASANOVA, ALBINA - University Of Texas
item REICHMANN, LARA - University Of Texas
item BONNETTE, JASON - University Of Texas
item ASPINWALL, MIKE - Western Sydney University
item HAWKES, CHRISTINE - University Of Texas
item JUENGER, THOMAS - University Of Texas
item Fay, Philip

Submitted to: Ecological Society of America Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 5/30/2014
Publication Date: 8/10/2014
Citation: Khasanova, A., Reichmann, L.G., Bonnette, J., Aspinwall, M., Hawkes, C.V., Juenger, T., Fay, P.A. 2014. Genotype and plant trait effects on soil CO2 efflux responses to altered precipitation in switchgrass. In: Proceedings of the Ecological Society of America, August 10-15, 2014, Sacramento, California. 2014 CDROM.

Interpretive Summary:

Technical Abstract: Background/Question/Methods Global climate change models predict increasing drought during the growing season, which will alter many ecosystem processes including soil CO2 efflux (JCO2), with potential consequences for carbon retention in soils. Soil moisture, soil temperature and plant traits such as leaf nitrogen content, leaf photosynthesis (ACO2), leaf area index (LAI), and above ground biomass (AGB) are typically good predictors of JCO2, and often differ among plant genotypes adapted to different climates. We examined how changes in amount of annual precipitation affected JCO2 in switchgrass, Panicum virgatum. We hypothesized that soil carbon flux will differ among genotypes of P. virgatum and that this response will differ depending on annual precipitation amount received. Ten genotypes of P. virgatum from divergent climatic origins were established under a rainout shelter in Temple, Texas, USA. Genotypes received five precipitation scenarios, representing the driest 10 percent to the wettest 10 percent of the historic rainfall record, in a completely randomized block design. JCO2 was measured monthly in low, mean, and high precipitation treatments. In June, JCO2 was measured in all genotypes and treatments, and leaf nitrogen, LAI, ACO2, and AGB in four representative genotypes. Results/Conclusions We found evidence for precipitation, genotype, and plant trait effects on JCO2 of switchgrass. JCO2 increased 1.41-fold from low to high precipitation (P=0.0084), and 1.39-fold among genotypes (P<0.0001), with similar genotype differences in all precipitation treatments (P = 0.25). JCO2 peaked in June, and peak JCO2 increased 1.47-fold with precipitation amount (P = 0.02). JCO2 increased with soil temperature (P<0.0001), but decreased with soil moisture (P<0.0001), and the highest JCO2 rates occurred during drier summer months, indicating that temperature was the main control on JCO2. A significant precipitation treatment x soil temperature interaction (P<0.0001) showed that JCO2 increased more strongly with soil temperature in the high precipitation treatment. Plant traits explained part of the genotype and precipitation effects on JCO2. JCO2 increased with leaf nitrogen content (P=0.01) and JCO2 varied in genotype interactions with leaf N and AGB (P=0.01, P=0.05). There were no three way interactions with precipitation treatment, which indicate that genotypic variation in biomass and leaf N affected JCO2 similarly across precipitation treatments. ACO2 and LAI were unrelated to JCO2. Thus plant traits related to nitrogen investment and growth contributed to precipitation and genotype effects on JCO2 in switchgrass, and may have consequences for soil carbon dynamics.