Germination and Establishment of Salsola in Relation to Seedbed Environment. II. Seed Distribution, Germination, and Seedling Growth of Salsola and Microenvironmental Monitoring of the Seedbed1

Abstract The purpose of this study was to ascertain when and under what conditions seed germination and seedling growth of Russian thistle (Salsola kali var. tenuifolia Tausch.) occurs in the field. Continuous monitoring of temperature and moisture parameters of the seedbed microenvironment was conducted during critical periods of germination and seedling growth. Seedling emergence was sampled weekly concurrent with seedbed monitoring. Seed dispersal investigations and seedling emergence studies in relation to burial depth were also carried on. Seed germination and seedling emergence of Russian thistle commenced in midwinter and early spring with below 0 C night temperatures alternating with 10‐ to 19‐C day temperatures. Optimum emergence occurred in March, with temperatures of 0 to 5 C alternating with those of 12 to 25 C. Afterripening requirements curtailed germination of 1970 seeds, compared with those of 1968, at early dates, but by March no depression occurred. Soil moisture potentials less than —15 bars reduced seedling emergence and increased mortality. Low relative humidity at the soil surface during the day curtailed establishment of plants from surface seeds. Seed burial, litter cover, and variable microtopography were all conducive to establishment of Russian thistle.