No growth stimulation of Canada's boreal forest under half-century of combined warming and CO2 fertilization

Martin P. Girardin, Olivier Bouriaud, Edward H. Hogg, Werner Kurz, Niklaus E. Zimmermann, Juha M. Metsaranta, Rogier De Jong, David C. Frank, Jan Esper, Ulf Büntgen, Xiao Jing Guo, Jagtar Bhatti

Research output: Contribution to journalArticlepeer-review

234 Scopus citations

Abstract

Considerable evidence exists that current global temperatures are higher than at any time during the past millennium. However, the long-term impacts of rising temperatures and associated shifts in the hydrological cycle on the productivity of ecosystems remain poorly understood for mid to high northern latitudes. Here, we quantify species-specific spatiotemporal variability in terrestrial aboveground biomass stem growth across Canada's boreal forests from 1950 to the present. We use 873 newly developed tree-ring chronologies from Canada's National Forest Inventory, representing an unprecedented degree of sampling standardization for a largescale dendrochronological study. We find significant regional- and species-related trends in growth, but the positive and negative trends compensate each other to yield no strong overall trend in forest growth when averaged across the Canadian boreal forest. The spatial patterns of growth trends identified in our analysis were to some extent coherent with trends estimated by remote sensing, but there are wide areas where remote-sensing information did not match the forest growth trends. Quantifications of tree growth variability as a function of climate factors and atmospheric CO2 concentration reveal strong negative temperature and positive moisture controls on spatial patterns of tree growth rates, emphasizing the ecological sensitivity to regime shifts in the hydrological cycle. An enhanced dependence of forest growth on soil moisture during the late-20th century coincides with a rapid rise in summer temperatures and occurs despite potential compensating effects from increased atmospheric CO2 concentration.

Original languageEnglish (US)
Pages (from-to)E8406-E8414
JournalProceedings of the National Academy of Sciences of the United States of America
Volume113
Issue number52
DOIs
StatePublished - Dec 27 2016

Keywords

  • Climate change
  • Dendrochronology
  • Drought impacts
  • Ecology
  • Normalized difference vegetation index

ASJC Scopus subject areas

  • General

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