title: Influence of warming on soil water potential controls  seedling mortality in perennial but not annual species  in a temperate grassland.
abstract: In a water-limited system, the following hypotheses are proposed: warming will increase seedling mortality; elevated atmospheric CO2 will reduce seedling mortality by reducing transpiration, thereby increasing soil water availability; and longevity (i.e. whether a species is annual or perennial) will affect the response of a species to global changes. Here, these three hypotheses are tested by assessing the impact of elevated CO2 (550 micromol mol(-1) and warming (+2 degrees C) on seedling emergence, survivorship and establishment in an Australian temperate grassland from autumn 2004 to autumn 2007. Warming impacts on seedling survivorship were dependent upon species longevity. Warming reduced seedling survivorship of perennials through its effects on soil water potential but the seedling survivorship of annuals was reduced to a greater extent than could be accounted for by treatment effects on soil water potential. Elevated CO2 did not significantly affect seedling survivorship in annuals or perennials. These results show that warming will alter recruitment of perennial species by changing soil water potential but will reduce recruitment of annual species independent of any effects on soil moisture. The results also show that exposure to elevated CO2 does not make seedlings more resistant to dry soils.
authors.affiliation: School of Plant Science, University of Tasmania, Hobart, 7001, Tasmania, Australia.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Hovenden
authors.affiliation: Land & Environmental Management, AgResearch, Palmerston North, New Zealand.
authors.forename: Paul C D
authors.initials: PCD
authors.lastname: Newton
authors.affiliation: School of Plant Science, University of Tasmania, Hobart, 7001, Tasmania, Australia.
authors.forename: Karen E
authors.initials: KE
authors.lastname: Wills
authors.affiliation: School of Plant Science, University of Tasmania, Hobart, 7001, Tasmania, Australia.
authors.forename: Jasmine K
authors.initials: JK
authors.lastname: Janes
authors.affiliation: School of Plant Science, University of Tasmania, Hobart, 7001, Tasmania, Australia.
authors.forename: Amity L
authors.initials: AL
authors.lastname: Williams
authors.affiliation: School of Plant Science, University of Tasmania, Hobart, 7001, Tasmania, Australia.
authors.forename: Jacqueline K
authors.initials: JK
authors.lastname: Vander Schoor
authors.affiliation: School of Plant Science, University of Tasmania, Hobart, 7001, Tasmania, Australia.
authors.forename: Michaela J
authors.initials: MJ
authors.lastname: Nolan
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism; D017752:Greenhouse Effect; D008136:Longevity; D063245:Plant Development; D010944:Plants / Q000378:metabolism; D006109:Poaceae / Q000254:growth & development / Q000378:metabolism; D011891:Rain; D036226:Seedlings / Q000254:growth & development* / Q000378:metabolism / Q000502:physiology; D012987:Soil; D013648:Tasmania; D013696:Temperature; D014867:Water
chemical_list: D012987:Soil; D014867:Water; D002245:Carbon Dioxide