Negative impacts of high temperatures on growth of black spruce forests intensify with the anticipated climate warming.
An increasing number of studies conclude that water limitations and heat stress may hinder the capacity of black spruce (Picea mariana (Mill.) B.S.P.) trees, a dominant species of Canada's boreal forests, to grow and assimilate atmospheric carbon. However, there is currently no scientific consensus on the future of these forests over the next century in the context of widespread climate warming. The large spatial extent of black spruce forests across the Canadian boreal forest and associated variability in climate, demography, and site conditions pose challenges for projecting future climate change responses. Here we provide an evaluation of the impacts of climate warming and drying, as well as increasing [CO2 ], on the aboveground productivity of black spruce forests across Canada south of 60°N for the period 1971 to 2100. We use a new extensive network of tree-ring data obtained from Canada's National Forest Inventory, spatially explicit simulations of net primary productivity (NPP) and its drivers, and multivariate statistical modeling. We found that soil water availability is a significant driver of black spruce interannual variability in productivity across broad areas of the western to eastern Canadian boreal forest. Interannual variability in productivity was also found to be driven by autotrophic respiration in the warmest regions. In most regions, the impacts of soil water availability and respiration on interannual variability in productivity occurred during the phase of carbohydrate accumulation the year preceding tree-ring formation. Results from projections suggest an increase in the importance of soil water availability and respiration as limiting factors on NPP over the next century due to warming, but this response may vary to the extent that other factors such as carbon dioxide fertilization, and respiration acclimation to high temperature, contribute to dampening these limitations.
Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du P.E.P.S, P.O. Box 10380, Stn. Sainte-Foy, Quebec, QC, G1V 4C7, Canada.
Martin P
MP
Girardin
Natural Resources Canada, Canadian Forest Service, Northern Forestry Centre, 5320 122nd Street, Edmonton, AB, T6H 3S5, Canada.
Edward H
EH
Hogg
Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du P.E.P.S, P.O. Box 10380, Stn. Sainte-Foy, Quebec, QC, G1V 4C7, Canada.
Pierre Y
PY
Bernier
Natural Resources Canada, Canadian Forest Service, Pacific Forestry Centre, 506 Burnside Road West, Victoria, BC, V8Z 1M5, Canada.
Werner A
WA
Kurz
Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du P.E.P.S, P.O. Box 10380, Stn. Sainte-Foy, Quebec, QC, G1V 4C7, Canada.
Xiao Jing
XJ
Guo
Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du P.E.P.S, P.O. Box 10380, Stn. Sainte-Foy, Quebec, QC, G1V 4C7, Canada.
Guillaume
G
Cyr
D002170:Canada; D002245:Carbon Dioxide; D002980:Climate; D057231:Climate Change; D008962:Models, Theoretical; D028222:Picea / Q000254:growth & development*; D012987:Soil / Q000737:chemistry; D066188:Taiga; D013696:Temperature; D014867:Water / Q000032:analysis
D012987:Soil; D014867:Water; D002245:Carbon Dioxide
Canada; carbon; climate change; dendroclimatology; drought; process-based model 3PG; respiration; semipartial correlation