Effects of climate change on plant regeneration from seeds in the cold deserts of Central Asia

More than 80% of the world’s cold deserts occur in Central Asia (CA). During the last 100 years, surface air temperature and annual precipitation have increased in CA, and these increases are predicted to continue through the 21st century. Additionally, atmospheric nitrogen (N) deposition has increased in the past 30 years and is predicted to continue to do so in the future. Much of the research that can be related to the effects of climate change on plant regeneration from seeds in the cold deserts of CA has focused on precipitation, with emphasis on plant life history. Seeds of many herbaceous species in the cold deserts of CA have physiological dormancy (PD), which is broken in summer, and some have physical dormancy (PY), which is broken in summer and/or winter. Due to low precipitation in autumn in most years, germination is delayed until spring. Thus annual species with PD and some with PY may behave as winter/spring annuals and/or spring ephemeral annuals. Seeds of annual species in hand-watered soil (supplemental water) begin to germinate earlier and to higher percentages in autumn than seeds in nonwatered soil (natural precipitation). In most studies, increased precipitation (hand-watering), N, and precipitation plus N increased seedling survival, growth, and seed production of spring and/or autumn-germinating plants. For diaspore heteromorphic species, watering increased the ratio of (high dispersal–low dormancy)/(low dispersal–high dormancy) diaspores. Increased precipitation, temperatures, and N deposition already are causing increases in density of plant cover of annual species and encroachment of shrubs into herbaceous plant communities in CA.