Germination responses to daylength and temperature in 8 species of Gobi desert plants used for ecological restoration
Mongolia is experiencing three major ecological stressors in the form of a mining boom, planet-wide climate change and livestock overgrazing. These factors most strongly intersect in desert and desert-steppe regions where the largest mines are placed and where ecosystem resilience to overgrazing and desertification is lowest. Human-mediated reintroduction of native plant species has been attempted at degraded sites, but lack of ecological information about optimal germination conditions has led to low success rates as artificially distributed seeds are wind- or animal-redistributed before germination at the target site. Additionally, lack of ecological knowledge about ideal germination windows inhibits research into other factors that impact these species in the field and the lab.
To investigate germination in natural conditions, I used a growth chamber to simulate a range of temperature and light parameters that occur during the Gobi warm season for seeds of 8 abundant plant species that are currently used in reclamation: (Amaryllidaceae) Allium mongolicum, Allium polyrhizum; (Poaceae) Setaria viridis; (Amaranthaceae) Anabasis brevifolia, Kalidium gracile, Salsola passerina; (Nitrariaceae) Nitraria sibirica; (Tamaricaceae) Reaumuria soongorica. Seeds of each species on agar plates were subjected to 10-, 13-, and 16-hour daylight and full darkness at 10°C, and the number of germinants was recorded daily.
Preliminary results of this ongoing study indicate that at 10°C, germination of K. gracile and S. viridis is unaffected by light exposure, while both A. mongolicum and A. polyrhizum germinate most rapidly in full darkness. However, the two Allium species differ in that while A. mongolicum showed no significant difference in germination rate of seeds exposed to any amount of daylight, seeds of A. polyrhizum germinated significantly more slowly under a 10-hour day than either 13- or 16-hour days. Almost all seeds of N. sibirica failed to germinate in the first trial at this temperature, preventing rate comparisons from the current data for the species. 10°C trials for A. brevifolia, S. passerina, and R. soongorica are still ongoing.
The full results, to be collected by April 2015, will include fully orthogonal comparisons of 15, 20, and 25 degree temperatures to each daylength and species described here. The complete study has the potential to significantly improve the effectiveness of ecological restoration efforts. In particular, if germination data can be used to inform a succession-based approach to the order and timing of distribution for species in field sites, the speed and resource efficiency of plant reintroduction may be greatly increased.