Abstract:

Aims Our objective was to study the effects of depth and duration of seed burial in the field on seed dormancy release and soil seed bank dynamics of three desert plants.
Methods The field burial experiment was conducted during an 18-month period at the site of the original seed collection at Alax Desert of Nei Mongol, China during April 2008 to October 2009. The species included Lespedeza potaninii, Nitraria tangutorum and Peganum nigellastrum with the dormancy of 98%, 95% and 3%, respectively, at the beginning of burial (stored 6 months at 5 °C since harvested). Four burial depths were used: 0, 2, 5 and 10 cm.
Important findings Dormancy release patterns were different among the three species. The dormancy percentage of L. potaninii seeds decreased from 98% at date of burial to 64% after 18-month burial on the soil surface (0 cm); lower decreases were observed when buried at 2, 5 and 10 cm (82% to 87%). Dormancy in N. tangutorum dropped from 95% to 1% after 6-month burial in the field. In contrast to these species, P. nigellastrum seeds exhibited seasonal pattern (dormancy cycle) during the experimental period. The maximum points of dormancy were observed in October in each of the two years, decreasing thereafter with dormancy of 3% when buried. The speed of dormancy release increased in N. tangutorum as the soil burial depth increased, but decreased in P. nigellastrum. At the end of 18-month burial, the field-germinated seeds on average of different buried depths were 11%, 12% and 8% for L. potaninii, N. tangutorum and P. nigellastrum, respectively; the average laboratory germinations were 3%, 74% and 42%, and dead seeds averaged 3%, 15% and 10%, respectively. According to the soil seed bank classification proposed by Thompson and Grime (1979), L. potaninii, N. tangutorum and P. nigellastrum had persistent seed banks.

Key words: germination, Lespedeza potanimii, Nitraria tangutorum, Pegamum nigellastrum, seed dormancy release, soil burial, soil seed bank