Desert Saltgrass Seed Germination and Seedbed Ecology

Abstract

Desert saltgrass [Distichlis spicata var. stricta (Torr.) Beetle] is an important forage species of the saline-alkali basins of the western United States. Revegetation of disturbed sites using saltgrass currently involves the use of rhizomes, but seeding saltgrass with conventional equipment would be much more efficient. The seed and seedbed ecology of desert saltgrass is important to land managers who wish to try new revegetation techniques. The germination of nine collections of saltgrass seed was determined at a wide range of constant and alternating temperatures. The effects of decreasing osmotic potentials on seed germination of one collection was determined using polyethylene glycol and sodium chloride solutions. Seedbed temperatures and moisture potentials were determined during the growing season in two saltgrass stands using thermocouple temperature probes and psychrometers. The temperature regime that produced the highest mean germination (58%) for all nine collections was 10 degrees C for 16 hours alternating with 40 degrees C for 8 hours (10/40 degrees C). Germination response varied significantly (P=0.01) between collections. The best germination was 96% with one collection at the 10/50 degrees C regime, but most collections germinated best with 10/40 degrees C regime. For all collections, at least a 20 degrees C diurnal fluctuation in temperature was needed for germination above 10%. Seeds did not germinate at temperatures as cold as -5 degrees C or as hot as 60 degrees C. Saltgrass germination was enhanced at osmotic potentials of -1 bar, but inhibited by potentials lower than -1 bar. No significant (P=0.01) germination occurred at -15 bars. Field seedbed temperatures reached optimum levels for germination after moisture potentials were below that required for germination. This suggests that saltgrass seed germination is an episodic event in nature, occurring only when moisture events coincide with optimum seedbed temperatures and can leach sufficient salts to raise moisture potentials above -15 bars.