Seed germination responses to temperature and dry storage of seven Caragana (Fabaceae) species from northwest China

Caragana shrublands are the main type of vegetation in some cold desert ecosystems in Xinjiang in northwest China, and information on seed dormancy and germination of Caragana species is needed to help restore disturbed areas. Freshly matured seeds of Caragana aurantiaca, C. dasyphylla C. polourensis, C. roborovskyi, C. soongorica, C. spinosa and C. tekesiensis, collected from three natural ecosystems were tested for germination in light at 15/5, 20/10, 25/15 and 30/15 °C after dry storage at room temperature for 1 week and 9 months. Depending on the species, 1–84% of the seeds had physical dormancy (i.e., water-impermeable seeds). At 15/5, 20/10, 25/15 and 30/15 °C, fresh seeds of C. aurantiaca, C. spinosa and C. dasyphylla germinated from 74% to 100%, those of C. soongorica 15% to 52% and those of C. roborovskyi and C. polourensis 13–73%. After 9 months of storage, germination percentages increased significantly over wide range of temperatures for seeds of C. soongorica, C. tekesinsis C. roborovskyi and C. polourensis but decreased significantly for C. spinosa and C. dasyphylla. Most fresh seeds of the floodplain species and desert species are water-permeable and can germinate over a wide range of temperatures; consequently, they could be planted in the field at any time during the growing season. Dry storage of seeds of C. roborovski and C. tekesiensis increased the percentage of water-permeable seeds. Seeds of these species germinate best at high temperatures and should be planted in summer. If C. polourensis is used for restoration, the seeds need to be scarified before planting.