title: Dormancy cycling and persistence of seeds in soil of a cold desert halophyte shrub.
abstract: OBJECTIVE
  Formation of seed banks and dormancy cycling are well known in annual species, but not in woody species. In this study it was 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 and water stress. Seedling emergence and dynamics of the soil seed bank were investigated in the field.
  
  
  RESULTS
  Seeds of K. gracile had a soil seed bank of 7030 seeds m(-2) 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 annual ND/CD cycle 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.
authors.affiliation: State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
authors.forename: Dechang
authors.initials: D
authors.lastname: Cao
authors.forename: Carol C
authors.initials: CC
authors.lastname: Baskin
authors.forename: Jerry M
authors.initials: JM
authors.lastname: Baskin
authors.forename: Fan
authors.initials: F
authors.lastname: Yang
authors.forename: Zhenying
authors.initials: Z
authors.lastname: Huang
mesh_terms: D027703:Amaranthaceae / Q000254:growth & development* / Q000502:physiology; D003080:Cold Temperature; D003889:Desert Climate; D018525:Germination; D057445:Plant Dormancy / Q000502:physiology*; D054712:Salinity; D055051:Salt-Tolerant Plants / Q000254:growth & development / Q000502:physiology; D012639:Seeds / Q000254:growth & development*; D012987:Soil
chemical_list: D012987:Soil
keywords: Cold desert habitat; Kalidium gracile; dormancy cycling; halophyte; salt tolerance; seed germination; seedling recruitment; soil seed bank