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Title: Disentangling root responses to climate change in a semiarid grassland

Author
item CARRILLO, YOLIMA - University Of Sydney
item PENDALL, ELISE - University Of Wyoming
item DIJKSTRA, FEIKE - University Of Sydney
item Lecain, Daniel
item Morgan, Jack
item Blumenthal, Dana
item Waldron, Sarah

Submitted to: Oecologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/2/2014
Publication Date: 3/19/2014
Citation: Carrillo, Y., Pendall, E., Dijkstra, F., Lecain, D.R., Morgan, J.A., Blumenthal, D.M., Waldron, S.E. 2014. Disentangling root responses to climate change in a semiarid grassland. Oecologia. DOI: 10.1007/s00442-014-2912-z.

Interpretive Summary: The ultimate response of grasslands to climate change is expected to be driven in large part by biological activity in the soil. In particular, the death and decomposition of organic matter in soils which cycles essential nutrients needed in plant growth may ultimately determine how plant productivity and the storage of carbon in soil organic matter react to climate change. A field experiment in which ambient CO2 concentration and temperature were manipulated to mimic conditions in the latter half of this century was conducted in a native prairie in southeaster Wyoming to understand how such grasslands will be affected by climate change. The results suggest that while combined warming and rising CO2 may stimulate plant production in relatively short-term experiments, the long-term consequences of such environmental changes in this grassland may be constrained by eventual loss of soil organic matter through increased decomposition and a slower cycling of nitrogen between soils and plants.

Technical Abstract: Future ecosystem properties of grasslands will be driven largely by belowground plant biomass responses to climate change, whose understanding has been limited by experimental and technical constraints. We use a multi-faceted approach and a factorial field experiment to explore impacts of elevated CO2 and warming on root C and N dynamics in a semiarid, temperate, native grassland. We assessed root standing crop, morphology, appearance/disappearance, and mass and N loss during decomposition of roots of two dominant grass species (C3, C4) at the Prairie Heating and CO2 Enrichment experiment (PHACE). Greater root standing crops under elevated CO2 resulted from increased production combined with decreased death. Warming altered production but concomitant death responses prevented changes in standing crops. Decomposition increased under environmental conditions generated by elevated CO2, but not warming, likely due to water limitation. Combined warming and elevated CO2 increased surface area, likely due to accelerate decomposition. Elevated CO2, particularly when combined with warming, slowed N release from the C4. Greater litter decomposition rates in future conditions may offset increased C inputs with greater biomass, therefore limiting net C accrual. Increased N retention in decomposing litter may be a mechanism slowing down N cycling, potentially altering N availability for plants and microbes.