title: Impacts of climate change drivers on C4 grassland productivity: scaling driver effects through the plant community.
abstract: Climate change drivers affect plant community productivity via three pathways: (i) direct effects of drivers on plants; (ii) the response of species abundances to drivers (community response); and (iii) the feedback effect of community change on productivity (community effect). The contribution of each pathway to driver-productivity relationships depends on functional traits of dominant species. We used data from three experiments in Texas, USA, to assess the role of community dynamics in the aboveground net primary productivity (ANPP) response of C4 grasslands to two climate drivers applied singly: atmospheric CO2 enrichment and augmented summer precipitation. The ANPP-driver response differed among experiments because community responses and effects differed. ANPP increased by 80-120g m(-2) per 100 μl l(-1) rise in CO2 in separate experiments with pasture and tallgrass prairie assemblages. Augmenting ambient precipitation by 128mm during one summer month each year increased ANPP more in native than in exotic communities in a third experiment. The community effect accounted for 21-38% of the ANPP CO2 response in the prairie experiment but little of the response in the pasture experiment. The community response to CO2 was linked to species traits associated with greater soil water from reduced transpiration (e.g. greater height). Community effects on the ANPP CO2 response and the greater ANPP response of native than exotic communities to augmented precipitation depended on species differences in transpiration efficiency. These results indicate that feedbacks from community change influenced ANPP-driver responses. However, the species traits that regulated community effects on ANPP differed from the traits that determined how communities responded to drivers.
authors: USDA-Agricultural Research Service, Grassland, Soil & Water Research Laboratory, Temple, Texas, 76502, USA wayne.polley@ars.usda.gov.
authors: H Wayne
authors: HW
authors: Polley
authors: USDA-Agricultural Research Service, High Plains Grasslands Research Station, Cheyenne, Wyoming, 82009, USA.
authors: Justin D
authors: JD
authors: Derner
authors: Nicholas School of the Environment, Duke University, Durham, North Carolina 27708, USA Biology Department, Duke University, Durham, North Carolina 27708, USA.
authors: Robert B
authors: RB
authors: Jackson
authors: Department of Ecology, Evolution and Organismal Biology, Iowa State University, Ames, Iowa 50011, USA.
authors: Brian J
authors: BJ
authors: Wilsey
authors: USDA-Agricultural Research Service, Grassland, Soil & Water Research Laboratory, Temple, Texas, 76502, USA.
authors: Philip A
authors: PA
authors: Fay
mesh_terms: D018533:Biomass; D002245:Carbon Dioxide / Q000378:metabolism*; D057231:Climate Change; D003710:Demography; D065948:Grassland; D018526:Plant Transpiration / Q000502:physiology*; D006109:Poaceae / Q000502:physiology*; D013781:Texas; D014867:Water / Q000502:physiology*
chemical_list: D014867:Water; D002245:Carbon Dioxide
keywords: Atmospheric CO2 concentration; C4 perennial grassland; evapotranspiration; exotic plants; pasture; plant community composition; precipitation; tallgrass prairie; transpiration efficiency; water-use efficiency.