ARS | Publication request: The fitness costs of delayed germination and diminutive growth response of cheatgrass

Submitted to: Society for Range Management Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: August 15, 2012
Publication Date: February 3, 2013
Citation: Harmon, D.N., Clements, C.D. 2013. The fitness costs of delayed germination and diminutive growth response of cheatgrass [abstract]. In: Proceedings of the Society for Range Management, February 3-7, 2013, Oklahoma City, OK. 66:60.

Technical Abstract: The competitive ability of cheatgrass is often attributed to rapid early season germination. Our previous research has observed germination occurring from October through June near the Reno, Nevada ARS research location. In a controlled experiment we allowed cheatgrass to germinate naturally (October 2010) and then later in March (2011). Maturation date and biomass were then compared. Plants that had delayed germination matured later (~ 4weeks), had significantly smaller biomass (March germination=0.48g, October germination=8.48g), and had a greater percent occurrence of seed smut (March germination=22%, October germination=3%). These results indicate a large fitness cost of delayed germination. To further examine the cost of delayed germination we conducted an experiment with intraspecific competition. We previously found that in greenhouse competition experiments if native annuals were allowed to germinate four weeks prior to cheatgrass germination (an anomaly in nature), cheatgrass has very diminutive growth (biomass=0.57g after 24 weeks growth compared to 5g without competition). In 2012 we conducted an experiment to determine these results with intraspecific competition. We again found that if a target cheatgrass plant was started in a pot a few weeks after other competing cheatgrass seedlings germinate it had very diminutive growth, indicating resource depletion by the earlier germinating competitors. Soil nutrition analysis however did not find a drastic decrease in nutrients below the growth potential of cheatgrass. This possibly indicates a growth response mechanism triggered by earlier germinating plants occupying space, either above ground or in root zones.