Variation in timing of planting influences bluebunch wheatgrass demography in an arid system

Authors: Boyd, Chad; James, Jeremy

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/1/2013
Publication Date: 3/1/2013
Citation: Boyd, C.S., James, J.J. 2013. Variation in timing of planting influences bluebunch wheatgrass demography in an arid system. Rangeland Ecology and Management. 66(2):117-126. https://doi.org/10.2111/REM-D-11-00217.1.
DOI: https://doi.org/10.2111/REM-D-11-00217.1

Interpretive Summary: Establishment of perennial grasses from seed in post-disturbance Wyoming big sagebrush communities has experienced limited success, due, in part, to a lack of knowledge of the seedling ecology of perennial grasses. We examined the influence of planting timing (September, October, November or December) on germination and seedling demographics of bluebunch wheatgrass (Pseudoroegneria spicata (Pursh) A. Love) at the Northern Great Basin Experimental Range near Burns, OR. Our results suggest that: 1) seed germination is high (up to 80%) for September and October planting and occurs in fall/winter whereas later plantings had reduced germination mainly in spring, 2) seedling emergence is low (approximately 5 – 15% of germinated seeds) regardless of timing of planting, and 3) establishment of emergent seedlings is up to twice as high for November and December-planted plots (up to approximately 75%). Our data indicate that timing of and performance at critical stages of seedling development were affected by planting date and suggest that it may be possible to use emerging technologies (e.g., seed coatings) to produce variable chronologies of seedling development from single plantings that allow managers to exploit multiple temporal windows of opportunity for seedling establishment.

Technical Abstract: Establishing perennial grasses from seed in postdisturbance Wyoming big sagebrush (Artemesia tridentata subsp. wyomingensis Welsh) communities is often unsuccessful, due in part to a lack of knowledge of the seedling ecology of perennial grasses. We examined the influence of planting timing on germination and seedling demography of bluebunch wheatgrass (Pseudoroegneria spicata [Pursh] A. Love) in the northern Great Basin. In 2008 (year 1) and 2009 (year 2) we planted seeds monthly, September–December, in 1-m2 plots (500 seeds per plot) using a randomized block design with five replications. Germination timing was indexed using seed bags placed adjacent to 1-m2 plots and retrieved at 2-wk intervals in fall and 1-mo intervals in spring. Seedlings were marked in March–June of the year following planting; seedlings alive in July were considered initially established. Planting in September and October had up to 80% germination prior to winter, whereas December plantings germinated mainly in spring and at reduced rates (15–35%). Seeds planted in September and October emerged approximately a month earlier than November–December plantings. The percentage of germinated seeds that emerged was highest for September–October plantings but the percentage of emergent seeds surviving to the end of the first growing season was highest for later plantings. Final seedling density was lowest for November planting in year 1 and highest for September and October planting in year 2. Our data indicate that timing of and performance at critical stages of seedling development were affected by planting month. We suggest that it may be possible to use emerging technologies (e.g., seed coatings or germplasm manipulations) to produce variable chronologies of seedling development with single plantings and allow managers to exploit multiple temporal windows of opportunity for seedling establishment.