title: Effects of increasing root carbon investment on the mortality and resprouting of Haloxylon ammodendron seedlings under drought.
abstract: Tree mortality induced by drought is one of the most complex processes in ecology. Although two mechanisms associated with water and carbon balance are proposed to explain tree mortality, outstanding problems still exist. Here, in order to test how the root system benefits survival and resprouting of Haloxylon ammodendron seedlings, we examined the various water- and carbon-related physiological indicators (shoot water potential, photosynthesis, dark respiration, hydraulic conductance and non-structural carbohydrates [NSC]) of H. ammodendron seedlings, which were grown in drought and control conditions throughout a grow season in greenhouse. The survival time of the seedling root system (died 70 days after drought) doubled the survival time of the shoot (died at 35 days). Difference in survival time between shoot and root resulted from sustained root respiration supported by increased NSC in roots under drought. Furthermore, investment into the root contributed to resprouting following drought. Based on these results, a death criterion is proposed for this species. The time sequence of major events indicated that drought shifted carbon allocation between shoot and root and altered the flux among different sinks (growth, respiration or storage). The interaction of water and carbon processes determined death or survival of droughted H. ammodendron seedlings. These findings revealed that the 'root protection' strategy is critical in determining survival and resprouting of this species, and provided insights into the effects of carbon and water dynamics on tree mortality.
authors.affiliation: State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, Xinjiang, China.|University of Chinese Academy of Sciences, Beijing, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, Xinjiang, China.|College of Life Science, Shihezi University, Shihezi, China.
authors.forename: J-B
authors.initials: JB
authors.lastname: Xie
authors.affiliation: State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, Xinjiang, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Li
mesh_terms: D027703:Amaranthaceae / Q000254:growth & development / Q000502:physiology*; D050260:Carbohydrate Metabolism; D002244:Carbon / Q000378:metabolism*; D055864:Droughts; D010100:Oxygen / Q000378:metabolism*; D010788:Photosynthesis; D018515:Plant Leaves / Q000254:growth & development / Q000502:physiology; D018517:Plant Roots / Q000254:growth & development / Q000502:physiology; D018520:Plant Shoots / Q000254:growth & development / Q000502:physiology; D018526:Plant Transpiration; D036226:Seedlings / Q000254:growth & development / Q000502:physiology; D013312:Stress, Physiological; D014867:Water / Q000378:metabolism*
chemical_list: D014867:Water; D002244:Carbon; D010100:Oxygen
keywords: Carbon starvation; drought; hydraulic failure; mortality; non-structural carbohydrates; resprouting; root respiration