Effects of Moisture and Temperature on Germination of Idaho Fescue

Germination response to varying temperatures and water stress levels during a 30-day incubation period was observed in 4 eastern Oregon collections of Festuca iduhoensis Elmer. Seeds were selected from the following habitat types: Artemisia trident&a ssp. wyomingensis/Festuca iduhoensis (ARTRV/FEID), Pinus ponderosa Dougl./Festucu idahoensis (PIPO/FEID). One stand of each habitat type was sampled, except for the ARTRV/FEID habitat type where seed was selected from both a high and low elevation plant community. The low elevation stand will be designated ARTRV“L”/FEID. Incubation temperature treatments were held constant (f2’ C) and ranged in 5” C increments from 5’ C to 35” C. At 15, 20, and 250 C, water stresses of 0.0 MPa, -0.6 MPa, and -0.9 MPa were depressed using polyethylene glycol 6000. Collectively, maximum total germinationforall collections occurred at and above 10’ C and below 30” C. Germination percentages for seeds from ARTRW/FEID, ARTRV/FEID and PIPO/FEID habitat types at 10’ C were 93.0, 97.0, 91.9, and 88.8%, respectively. Maximum germination rates for all collections occurred between 20-25” C. As water stress decreased and temperature increased, both germination amount and rate for the 4 collections declined. Seeds of Idaho fescue collected from sagebrush habitat types maintained higher germination amounts and faster germination rates over wider temperature and moisture stress regime than did seeds selected from the PIPO/FEID site. Seed production and germination are important for the survival of plant species given the variable conditions of most natural ecosystems. Parameters which influence the adaptability and regeneration success of a species’ population include moisture stress and temperature (Eddleman 1979). Because moisture and temperature vary across environmental gradients, selective forces have probably resulted in the development of ecotypes sensitive to the climatic regimes of a given area (Turreson 1922). Reports examining germination characteristics of native species suggest ecotypic differences in response to variable incubation environments (Chouduri 1968, Capon et al. 1978, Lindauer and Quinn 1977, Workman and West 1967, Young and Evans 1981). However, relatively little research has examined germination response from seed collected along environmental gradients in local geographic areas. Authors are assistant professor, Rangeland Resources Department, Oregon State University, Cowallis 9733 I; associate professor. Eastern Oregon Agricultural Research Center. Star Rt. I-4.5 I Hwy. 205, Burns. Oregon 97720; and regional forest ecologist, Regional Office. U.S. Forest Service, Fed. Office Building, 324-25th Street, Ogden. Utah 84401. This research was a cooperative effort and jointly supported by the USDA, Agricultural Research Service and Eastern Oregon Agricultural Research Center, Squaw Butte Station, Agricultural Experiment Station. Tech. Paper NO. 7332. Oregon Agricultural Experiment Station. Manuscript accepted December 19, 1984. JOURNAL OF RANGE MANAGEMENT 38(4), July 1985 This research was designtd to evaluate germination response of 4 eastern Oregon seed collections of Idaho fescue to varying conditions of temperature and substrate water stress. Idaho fescue is a cool-season perennial bunchgrass indigenous to communities dominated by big sagebrush (Artemisia tridentata Nutt.) and ponderosa pine (Pinusponderosa Dougl.). Optimum germination temperatures for Idaho fescue have been reported to be between I5 to ’ C (Young et al. 1981, Stocker 1975). Materials and Methods Seed Collection and Processing Idaho fescue seeds were collected from the following habitat types: Artemisia tridentata ssp. wyomingensisl Festuca idahoensis (ARTRW/ FEID) (Doescher 1983), Artemisia tridentata ssp. vaseyana/Festuca idahoensis (ARTRV/ FEID) (Winward 1970) and Pinus ponderosal Festuca idahoensis (PIPO/ FEID) (Franklin and Dyrness 1973). One stand of each habitat type was sampled, except for the ARTRV/ FEID habitat type where seed was collected from both a high and low elevation plant community. The low elevation stand occurred on coarse pumice soils. For purposes of this discussion, this site will be referred to as the ARTRV“L’/ FEID habitat type. All habitat types were chosen in the same general geographic region (Table 1). It was assumed that ARTRW/ FEID habitat type was the most xeric, the PIP0 habitat type the most mesic and the ARTRV“L”/ FElDand ARTRV/ FEID habitat type intermediate in moisture relations. All sites had a dominant understory of Idaho fescue. Seeds of Idaho fescue were collected by hand stripping at various times during the 1980 growing season and cleaned by hand threshing and screening to remove caryopses from chaff. Seeds were stored at room temperatures. In order to standardize seed weight during experimentation, only heavy seeds were used in germination trials. Unfilled and light seeds were removed with a seed blower, with blower settings held constant for each seed lot. Abnormally developed embryos observed on a light table were not included in the germination experiments. Seeds used in experimentation were collected during seed shatter as test of seed viability with tetrazolim chloride indicated better stress germination from seeds collected during this phenological period. Seeds approximately 8 months of age were used in the germination trials. Experimental Procedure Seeds were concurrently germinated in environmental chambers under seven constant temperatures (5,10,15,20,25,30, and 35” C) and six combinations of temperature and water stress ( lS°C/O.O MPA, 15”C/-0.6MPa, 15°C/-0.9MPa,200C/0.0MPa,200C/-0.6