title: Experimental soil warming and cooling alters the partitioning of recent assimilates: evidence from a (14)C-labelling study at the alpine treeline.
abstract: Despite concerns about climate change effects on ecosystems functioning, little is known on how plant assimilate partitioning changes with temperature. Particularly, large temperature effects might occur in cold ecosystems where critical processes are at their temperature limit. In this study, we tested temperature effects on carbon (C) assimilate partitioning in a field experiment at the alpine treeline. We warmed and cooled soils of microcosms planted with Pinus mugo or Leucanthemopsis alpina, achieving daily mean soil temperatures (3-10 cm depth) around 5.8, 12.7 and 19.2 °C in cooled, control and warmed soils. We pulse-labelled these systems with (14)CO2 for one photoperiod and traced (14)C over the successive 4 days. Plant net (14)C uptake increased steadily with soil temperature. However, (14)C amounts in fungal hyphae, soil microbial biomass, soil organic matter, and soil respiration showed a non-linear response to temperature. This non-linear pattern was particularly pronounced in P. mugo, with five times higher (14)C activities in cooled compared to control soils, but no difference between warmed and control soil. Autoradiographic analysis of the spatial distribution of (14)C in soils indicated that temperature effects on the vertical label distribution within soils depended on plant species. Our results show that plant growth, in particular root metabolism, is limited by low soil temperature. As a consequence, positive temperature effects on net C uptake may not be paralleled by similar changes in rhizodeposition. This has important implications for predictions of soil C storage, because rhizodeposits and plant biomass vary strongly in their residence times.
authors: Institute of Evolutionary Biology and Environmental Studies, University of Zurich, 8057, Zurich, Switzerland. adele.ferrari@ieu.uzh.ch.|Forest Soils and Biogeochemistry, Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), 8903, Birmensdorf, Switzerland. adele.ferrari@ieu.uzh.ch.
authors: A
authors: http://orcid.org/0000-0002-6993-6531
authors: A
authors: Ferrari
authors: Forest Soils and Biogeochemistry, Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), 8903, Birmensdorf, Switzerland.
authors: F
authors: F
authors: Hagedorn
authors: Institute of Evolutionary Biology and Environmental Studies, University of Zurich, 8057, Zurich, Switzerland.
authors: P A
authors: PA
authors: Niklaus
mesh_terms: D019659:Asteraceae / Q000378:metabolism / Q000502:physiology*; D018533:Biomass; D002244:Carbon / Q000378:metabolism*; D057486:Carbon Cycle; D002245:Carbon Dioxide / Q000378:metabolism; D002247:Carbon Isotopes / Q000378:metabolism; D057231:Climate Change; D003080:Cold Temperature; D017753:Ecosystem; D006358:Hot Temperature; D010788:Photosynthesis; D028223:Pinus / Q000378:metabolism / Q000502:physiology*; D018517:Plant Roots / Q000378:metabolism / Q000502:physiology*; D018520:Plant Shoots / Q000378:metabolism / Q000502:physiology; D012987:Soil; D012988:Soil Microbiology; D013696:Temperature
chemical_list: D002247:Carbon Isotopes; D012987:Soil; D002245:Carbon Dioxide; D002244:Carbon
keywords: C isotopes; Carbon partitioning; Climate change; Leucanthemopsis alpina; Pinus mugo