Seasonal and Inter-Annual Variability in the Carbon and Water Balances of the Southern Boreal Forests of Western Canada

Transcription

1 Seasonal and Inter-Annual Variability in the Carbon and Water Balances of the Southern Boreal Forests of Western Canada Alan Barr 1, T. Andy Black 2, J. Harry McCaughey 3, Garth van der Kamp 4 1 Climate Research Division, Environment Canada; Global Institute for Water Security, U. of S. 2 Faculty of Land and Food Systems, U.B.C. 3 Department of Geography, Queen s U. 4 Water Science and Technology Directorate, Environment Canada

2 Outline Introduction Three short stories Summary

3 Boreal Ecosystem Research and Monitoring Sites (BERMS, 1994+) Southern edge of Boreal Plains ecozone Mean annual air temperature +0.4 o C Mean annual precipitation 467 mm

4 Eddy-Covariance Flux Towers The answer is blowing in the wind. 100 km Black Spruce Jack Pine Aspen Fen

5 Site History

6 Trembling Aspen (OA) Wildfire 1919 Silt loam, 8-10 cm LFH Water table at 1-3 m LAI ~ 4-5

7 Black Spruce (SOBS) Wildfire ~ cm peat Near-surface water table LAI ~ 3

8 Jack Pine (OJP, H75, H94, H02) Four stands: wildfire 1914; harvested 1975, 1994, 2002 Sandy soil, water table at ~ 7m OJP LAI ~ 2

9 Results: Story 1 Water balance at stand and basin scales Inter-annual variability in net ecosystem production Stocks, fluxes and tree mortality: two contrasting stands

10 White Gull Creek Watershed 603 km 2 Black Spruce 41% Wetlands 22% Aspen 17% Jack Pine 12% Harvested 8% OBS OA 100 km to SW OJP H75 H02 H94 Fen

11 White Gull Creek Streamflow Station OBS OJP H75 H02 H94 Fen

12 Annual Precipitation and Streamflow White Gull Creek, Oct-Sept Hydrologic Years Spruce Pine 467 mm

13 Annual Stand-Level Water Balance Box plots by Land-Cover Type P (mm y -1 ) E* ΔS Precipitation P Evapotranspiration E* Storage change ΔS Fen Harvest Pine Spruce Aspen Fen Harvest Pine Spruce Aspen Fen Harvest Pine Spruce Aspen

14 Annual Stand-Level Water Balance Box plots by Land-Cover Type P (mm y -1 ) E* ΔS Outflow = P-E*-ΔS Stream Fen Harvest Pine Spruce Aspen Fen Harvest Pine Spruce Aspen Fen Harvest Pine Spruce Aspen Fen Harvest Pine Spruce Aspen

15 Summary: Runoff Ratios (outflow to precipitation) Stand-level outflow ( ) 0.09 aspen 0.10 fen 0.26 black spruce 0.32 jack pine 0.41 harvested Basin streamflow ( ) 0.24 gauged

16 Annual Stand-Level Outflow in Relation to Gauged Streamflow White Gull Basin, Area-Weighted Mean of 7 Sites Black Spruce Basin Streamflow (mm y -1 )

17 Results: Story 2 Water balance at stand and basin scales Inter-annual variability in net ecosystem production Stocks, fluxes and tree mortality: two contrasting stands

18 Trembling Aspen Forest Leaf Area Index and Net Ecosystem Production NEP (15-d means) Warm springs Cool springs

19 Black Spruce Forest cm Soil Temperature and Net Ecosystem Production NEP (15-d means) Early thaw Late thaw

20 Across-Year Variability (Standard Deviation) of Net Ecosystem Production NEP (for averaging periods of 1 to 121 days) (g C m -2 d -1 ) Aspen Spruce Pine

21 Across-Year Correlation Coefficient Between NEP and Air Temperature (for averaging periods of 1 to 121 days) 1.0 Aspen 0.5 Spruce Pine -1.0

22 Across-Year Correlation Coefficient Between NEP and 5-cm Soil Temperature (for averaging periods of 1 to 121 days) 1.0 Aspen 0.5 Spruce Pine -1.0

23 Inter-Annual Variation in NEP in Relation to Growing-Season Length Aspen Spruce Pine Carbon-uptake period (days) Thawed period (days) Thawed period (days)

24 Results: Story 3 Water balance at stand and basin scales Inter-annual variability in net ecosystem production Stocks, fluxes and tree mortality: two contrasting stands

25 Annual Precipitation Dry Wet Aspen Jack Pine

26 Stem Density Changes: Aspen (1919) Jack Pine (1914)

27 Carbon Stock Changes: LFH forest floor Coarse Woody Debris Standing Dead Tree Biomass Aspen Jack Pine 2.2 n/a (t C ha -1 y -1 ) n/a LFH CWD StDead Tree n/a

28 Carbon Stock Changes: in Relation to Eddy-Covariance NEP Aspen Jack Pine n/a (t C ha -1 y -1 ) n/a LFH CWD StDead Tree ΣNEP

29 Inter-Annual Variation in Aspen NEP in Relation to Carbon-Uptake Period (No apparent effect of increased mortality !) Carbon-uptake period (days)

30 Summary: Stocks, Fluxes and Mortality Reasonable agreement between C fluxes and stock changes aspen C gains as necromass jack pine C gains as biomass Large climatically-driven increase in aspen mortality BUT no discernable impact on NEP, RE or GPP -- YET

31 Summary: Water Balance Tenfold inter-annual variation in streamflow (~ mm y -1 ) Large contrasts among land cover types in outflow / precipitation ratio: 9% aspen; 10% fen; 26% black spruce; 32% jack pine; 41% harvested; 24% basin

32 Summary: Inter-Annual Variability in Net Ecosystem Production Dominated by positive response to spring warming via GPP aspen via earlier leafout spruce and pine via earlier spring thaw Negative response to winter warming via RE Summer responses more complex; drought impacts both GPP and RE

33 Acknowledgements Barry Goodison, Charmaine Hrynkiw, Erin Thompson, Craig Smith, Dell Bayne, Randy Schmidt, Bruce Cole, Newell Hedstrom, Joe Eley, Anne Walker EC Bob Stewart, Ted Hogg. Jag Bhatti CFS Norm Stolle, Dave Wieder, Murray Peterson Parks Canada Zoran Nesic, Andrew Sauter, Kai Morgenstern, Natascha Kljun, Praveena Krishnan, Dom Lessard, Nick Grant, Rick Ketler UBC Dan Finch, Sheila McQueen, Lauren MacLean Queen s U. Environment Canada, CFS, Parks Canada Fluxnet-Canada, Canadian Carbon Program NSERC, CFCAS, BIOCAP Global Institute for Water Security, U of S Action Plan 2000 on Climate Change Climate Change Action Fund Program for Energy Research and Development