Date of Award:

1-1-1970

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Department name when degree awarded

Plant Physiology

Advisor/Chair:

Herman H. Wiebe

Abstract

The response of grass, forb, and shrub seeds to the subalpine environment during the fall and under winter snow and under laboratory conditions at 20/28 C was observed for 3 consecutive years at an elevation of about 3000m on the Wasatch Plateau in central Utah.

Seeds in nylon sleeves were planted under 2 cm of soil before snowfall. Under snow plantings were made directly on the soil surface and under 2 cm of soil. The seeds planted before snowfall were removed each year on four occasions: when under snow plantings were made, after snow depth exceeded 130 cm (deep snow), just before spring snowmelt, and 10 or more days following snowmelt when soils had warmed. Seeds planted under snow or under snow and soil were removed on two occasions: after snow depth exceeded 130 cm and just before the snow melted in the spring.

Environmental conditions which produced seed germination varied with species, origin of species, age of seed, and temperature. Fifty-four of the 60 species planted in September under 2 cm of soil before snowfall had some seed germinated when examined just before the snow melted in the spring. Fifty of the same species planted after winter snow covered the ground in November also had some seed germination just before the snow melted in the spring. Seed germination at the near 0 C temperatures on the soil surface under snow was usually similar to the comparable seed lots also placed under 2 cm of soil.

Germinability of the grasses, forbs, and shrubs studied was placed in three broad classifications: (1) Little or no seed dormancy with germination at low and warm temperatures. Seeds germinated soon after harvest at temperatures near 0 C and also in the laboratory at 20/28 C. Examples are Agropyron desertorum, A. intermedium, Chrysothamnus viscidiflorus, and Lupinus alpestris. (2) Little or no seed dormancy with germination only at warm temperatures. Seeds did not germinate at the low temperatures present in the subalpine zone during the fall and winter but germinated readily in the laboratory at 20/28 C. Examples are Aquilegia caerulea , Potentilla gracilis var. pulcherrima, Rudbeckia occidentalis, and Valeriana edulis. (3) Dormancy at seed harvest. Germination was usually increased by near 0 C temperatures, by aging, and by other environmental conditions present under deep snow. Examples are Agropyron trachycaulum, Delphinium barbeyi, Madia glomerata, and Ribes cereum var. inebrians.


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