2020 ESA Annual Meeting (August 3 - 6)

PS 8 Abstract - Effect of extreme drought on arbuscular mycorrhizal root colonization and functional traits of two C4 dominant grasses

Smriti Pehim Limbu, Earth and Planetary Sciences, Johns Hopkins University, Baltimore, MD and Meghan Avolio, Department of Earth & Planetary Sciences, Johns Hopkins University, Baltimore, MD
Background/Question/Methods

Functional plant traits reflect plant sensitivity to drought whereas arbuscular mycorrhizal fungi (AMF) can increase plant tolerance to drought. The objective of our study was to assess how extreme drought affects the fungal root colonization and functional traits of two dominant C4 grasses of tallgrass prairie, Andropogon gerardii and Sorghastrum nutans. The study was done in 2019 as a part of the Climate Extreme Experiment (CEE) established in 2010 in Konza Prairie Biological Station, Kansas. CEE had four treatments in 2019: 1) first drought, 2) second consecutive drought, 3) second drought with a long period of recovery, 4) third consecutive drought. Extreme drought was imposed by reducing growing season rainfall with plastic roofs. We hypothesized that the mean functional plant traits and fungal root colonization of the two grasses will differ in four treatments, indicating legacies of previous droughts. In June 2019, when all plants were experiencing the same drought, the youngest mature leaf of the grasses was clipped, scanned, and dried for specific leaf area analysis. Biweekly pre-dawn and mid-day leaf water potential were measured using pressure bomb. We also looked for fungal root colonization by staining the roots and counting the percentage colonized by intersect grid-line method.

Results/Conclusions

Predawn, and mid-day leaf water potential differed for all treatments and between A. gerardii and S. nutans. A. gerardii and S. nutans that received three consecutive drought treatment had the lowest pre-dawn and mid-day leaf water potential and the highest leaf water potential was seen in the plants with first drought treatment. It seems that these grasses have some resistance to drought when exposed to drought for the first time but the resilience to drought seems to be low. A. gerardii had higher pre-dawn and mid-day leaf water potential than S. nutans in all treatments suggesting that S. nutans is more sensitive to drought than A. gerardii. In addition, the height of S. nutans remained the same for all the treatments while the height of A. gerardii responded to difference in treatments and was tallest under three consecutive drought and second drought with a long period of recovery. Specific leaf area and no. of leaves were not affected by treatments for either of the grass. We also found differences in fungal root colonization. We conclude that studying functional plant traits and fungal root colonization will help in understanding the ecosystem change, and grassland resistance and resilience to drought.