Dormancy cycling and persistence of seeds in soil of a cold desert halophyte shrub

Dechang Cao1,2, Carol C. Baskin3,4, Jerry M. Baskin3, Fan Yang1,2 and Zhenying Huang1,*

1State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China, 2Graduate School of Chinese Academy of Sciences, Beijing, 100039, China, 3Department of Biology and 4Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY 40546, USA
* For correspondence. E-mail zhenying@ibcas.ac.cn

Abstract

  • Background and Aims Formation of seed banks and dormancy cycling arewell known in annual species, but not in woodyspecies. In this study itwas hypothesized that the long-lived halophytic cold desert shrub Kalidium gracile has a seed bank and dormancy cycling, which help restrict germination to a favourable time for seedling survival.
  • Methods Fresh seeds were buried in November 2009 and exhumed and tested for germination monthly from May 2010 to December 2011 over a range of temperatures and salinities. Germination recovery and viability were determined after exposure to salinity andwater stress. Seedling emergence and dynamics of the soil seed bankwere investigated in the field.
  • Key Results Seeds of K. gracile had a soil seed bank of 7030 seeds m22 at the beginning of the growing season. About 72% of the seeds were depleted from the soil seed bank during a growing season, and only 1.4% of them gave rise to seedlings that germinated early enough to reach a stage of growth at which they could survive to overwinter. About 28% of the seeds became part of a persistent soil seed bank. Buried seeds exhibited an annual non-dormancy/ conditional dormancy (ND/CD) cycle, and germination varied in sensitivity to salinity during the cycle. Dormancy cycling is coordinated with seasonal environmental conditions in such a way that the seeds germinate in summer, when there is sufficient precipitation for seedling establishment. ?Conclusions Kalidium gracile has three life history traits that help ensure persistence at a site: a polycarpic perennial life cycle, a persistent seed bank and dormancy cycling. The annualND/CDcycle in seeds of K. gracile contributes to seedling establishment of this species in the unpredictable desert environment and to maintenance of a persistent soil seed bank. This is the first report of a seed dormancy cycle in a cold desert shrub.