Bottlebrush squirreltail Elymus elymoides and big squirreltail E.multisetus are variable, short-lived perennial bunchgrasses widespread in mid and western North America. There is interest in using them in rangeland restoration, in part for erosion control and because they may be able to outcompete the introduced invasive annual, cheatgrass Bromus tectorum which generally prevents native perennial grass establishment through competition for soil moisture, this enhanced by an ability to germinate at very low seedbed temperatures. This study assessed germination at a wide range of constant or alternating temperatures for squirreltail seeds collected from numerous locations, at Greenville Farm experimental site, Utah (41°54' N, 111°50'E) USA. Germination temperature profiles from this and previous work were compared to cheatgrass.
In the mid 1990s, squirreltail seed (collected from various populations in California, Colorado, Idaho, Montana, Nevada, Oregon, Utah and Washington states) were planted at Greenville Farm, and resultant seed used in the germination trials. Trials were conducted in the dark. Seeds were placed on germination paper in Petri dishes and kept moist with tap water.
Treatments (4 replications of 25 seeds each) comprised 55 constant or alternating incubation temperature regimes:
1) Constant incubation temperatures of 0, 2 and 5° C, and 5° increments up to 40° C.
2) Alternating regimes of 16 h at each constant temperature, plus 8 h at each higher temperature per 24 h (e.g. 35° C alternated with 40° C only; 0º C alternated with 2, 5, 10, 15, 20, 25, 30, 35 and 40° C).
Germination counts (seeds were considered germinated when the radical emerged 1 mm) were made at 1, 2 and 4 weeks incubation. Data from other trials (conducted in 1972, 1974, 1975 and 1999) are also included in the analysis to give a more comprehensive appraisal of germination responses of seed derived from a broad range of localities.
There was no single temperature regime that resulted in maximum germination for all squirreltail accessions (i.e. seed from different localities) tested, and seed of both species germinated over a wide temperature range. However, the regimes most frequently supporting highest germination (80-92%) were 15/20 and 15/25° C (i.e. moderate seedbed temperature).
The greatest variation in germination amongst seed derived from different localities occurred at very cold 0/0 (constant 0° C, 0/2 (0°C for 16 h and 2°C for 8 h in each 24 h), 0/5 and 2/2°C) and cold (0/10, 0/15, 2/5, 2/10, 2/15, 5/5 and 5/10°C) categories of seedbed temperatures; such differences may be important in selection of appropriate seed for field sowing. Interestingly germination at very cold (0 to 18%) and cold (up to 57%) seedbed temperatures was sometimes high and compared quite favourably to cheatgrass (37 and 72% repectively).
This suggests that the squirreltails show great potential to establish at cheatgrass dominated sites with the ability to germinate in late autumn and very early spring and at a wide range of temperatures.
If using or referring to this published study, please read and quote the original paper, this can be viewed at: https://www.uair.arizona.edu/holdings/journal/issue?r=http://jrm.library.arizona.edu/Volume56/Number3/