Seed production and seedling fitness are uncoupled from maternal plant productivity in three aridland bunchgrasses

Authors: DRENOVSKY, REBECCA - John Carroll University; THORNHILL, MEGAN - John Carroll University; KNESTRICK, MATTHEW - John Carroll University; DLUGOS, DANIEL - John Carroll University; Svejcar, Anthony; JAMES, JEREMY - University Of California Agriculture And Natural Resources (UCANR)

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2015
Publication Date: 1/20/2016
Citation: Drenovsky, R.E., Thornhill, M.L., Knestrick, M., Dlugos, D., Svejcar, A.J., James, J.J. 2016. Seed production and seedling fitness are uncoupled from maternal plant productivity in three aridland bunchgrasses. Rangeland Ecology and Management. 69(2016):161-168. https://doi.org/10.1016/j.rama.2016.01.003.
DOI: https://doi.org/10.1016/j.rama.2016.01.003

Interpretive Summary: On native rangelands, perennial bunchgrasses are critical for holding soil in place, competing with weeds, and providing forage for livestock and wildlife. Because these plants tend to live five to ten years, seed production and reestablishment is critical for maintaining rangeland health and productivity. We found that simply adding water and nutrients was not enough to increase seed production for the three native bunchgrasses we studied. The results show that past assumptions about high seed production in wet years may not be correct. More research on factors which control reproductive output of native perennial bunchgrasses is warranted.

Technical Abstract: Aridlands are degrading at alarming rates across the globe. Seedling recruitment in these disturbed systems is slow, and restoration seeding efforts targeted at accelerating recovery routinely fail. Our objective was to determine how the maternal plant resource environment influences seed and seedling dynamics in three perennial bunchgrass species (Elymus elymoides (Raf.) Sezey, bottlebrush squirreltail; Festuca idahoensis Elmer, Idaho fescue; and Pseudoroegneria spicata (Pursh) A. Löve, bluebunch wheatgrass). Using established plants in the field, we supplied water and nutrients in a factorial design and measured mother plant productivity and fecundity. In the laboratory, growth chamber, and field we assessed offspring performance to determine the strength of transgenerational effects. Overall, resource amendment increased mother plant growth but had no impact on seed production. Germination rates were high in both the laboratory and field, although seeds from irrigated mother plants tended to have higher field germination rates. Relative growth rate, leaf mass ratio, and relative root elongation rate (RRER) were highly variable, although RRER tended to be higher in seedlings derived from irrigated mother plants. In the field, seedling survivorship was low across all species, although survivorship doubled in seedlings from irrigated versus non-irrigated P. spicata mother plants. Overall, our results suggest growth and fecundity responses to resource amendment are decoupled in our suite of species, but that transgenerational effects can have significant, although variable, impacts among species. As a result, productivity responses to natural and anthropogenic changes in resource availability may not be strong predictors of how altered resource supply influences propagule production, seedling fitness, and ultimately plant community dynamics in these aridland systems.