Drought impacts on growth & dieback of forests in western Canada

Transcription

1 Drought impacts on growth & dieback of forests in western Canada Presented by E.H. (Ted) Hogg Northern Forestry Centre, Edmonton, Alberta Natural Resources Canada, Canadian Forest Service

2 Drought-induced forest dieback under climate change: an emerging global issue Some recent publications: Allen, CD Climate-induced forest dieback: an escalating global phenomenon? Unasylva 231/232 60(1-2): drought? Phillips et al Drought sensitivity of the Amazon rainforest. Science 323: Van Mantgem et al Widespread increase of tree mortality rates in the western United States. Science 323: Jump et al The altitude-for-latitude disparity in the range retractions of woody species. Trends in Ecol. & Evolution (in press) Estimated changes in growth (NPP) for the North American boreal forest from remote sensing (Bunn et al. 2007) Worrall et al Rapid mortality of Populus tremuloides in southwestern Colorado. For. Ecol Manage. 255: 686 Seagers et al Model projections of an immanent transition to a more arid climate in SW North America. Science 316: 1181 Bunn et al Northern high-latitude ecosystems respond to climate change. EOS 88: 333 Ciais et al Europe-wide reduction in primary productivity caused by the heat and drought in Nature 437: 529 Breshears et al Regional vegetation die-off in response to globalchange-type drought. PNAS 102:15144 Sudden aspen decline following drought across the intermountain west of the US, see

3 Drought-induced forest dieback under climate change: an emerging global issue Publication in press (Forest Ecology & Management): A global overview of drought and heat-induced tree mortality reveals emerging climate change risks for forests By Craig Allen (US Geol. Survey) and 19 co-authors from the US, Canada, Algeria, Argentina, Australia, China, France, Italy, Korea, Russia, Spain, Switzerland, & Turkey The paper highlights a recent increase in published reports of climaterelated forest mortality from all of the world s forested continents Drought-induced aspen mortality in western Canada photo by M. Michaelian Increase in % papers on forests reporting on drought & mortality An imperfect indicator in the absence of a global monitoring system for forests!

4 Impacts of the drought on aspen forests in western Canada Worst drought in >80 years across a large area in the Canadian prairie provinces of Saskatchewan & Alberta Severe mortality of aspen (Populus tremuloides) forests in the parkland (forest-prairie transition) zone Also caused mortality of conifers and urban forests Drought-damaged aspen leaves (2002) Alberta Sask. Manitoba Aerial view of aspen mortality (2004) Drought-caused dieback resembling fire effects Drought-affected area showing severe dieback of aspen forests

5 CIPHA study Climate Impacts on Productivity & Health of Aspen Initiated by Hogg, Brandt & Kochtubajda in 2000 (under CCAF & PERD) (Expanded to include Ontario through collaboration with Hopkin & Keizer, GLFC) Includes annual monitoring of aspen health across west-central Canada (e.g. dieback, mortality, defoliation, insects & diseases) Hierarchical design (30 study areas, total of 180 plots) Tree-rings & plot data used in estimation of changes in stand biomass (T ha -1 ) Linked with tower-based monitoring of carbon & water fluxes (BERMS Old Aspen site) BERMS Old Aspen flux tower Aspen tree-rings trees per plot 20 m 2 plots per stand 3 stands per site CIPHA study region

6 Climate Moisture Index (CMI) A simple tool for assessing moisture variation and drought severity in remote forested regions where long-term climate data are typically limited to temperature and precipitation CMI = P PET (units in cm/year) P is mean annual precipitation includes water input as both rain and snow PET is annual potential evapotranspiration loss of water vapour from a well-vegetated landscape P PET Method of estimating PET: runoff Simplified Penman-Monteith method (requires only max & min daily temperatures) Hogg (1997), Agric. For. Meteorol. 84:

7 Climate Moisture Index (CMI) Long-term CMI is closely correlated with vegetation zonation & hydrological gradients in ecosystem functioning (Hogg 1994) Used for drought risk assessments (e.g. Volney et al. 2005), projections of future climate change impacts (e.g. Hogg & Hurdle 1995) & reviews of options for adaptation (Henderson et al. 2002, Hogg & Bernier 2005, Lempriere et al. 2009). Boreal forest (CMI > 0) Parkland (CMI -15 to 0) Prairie (CMI < -15)

8 Climate Moisture Index (CMI) Long-term CMI is closely correlated with vegetation zonation & hydrological gradients in ecosystem functioning (Hogg 1994) Used for drought risk assessments (e.g. Volney et al. 2005), projections of future climate change impacts (e.g. Hogg & Hurdle 1995) & reviews of options for adaptation (Henderson et al. 2002, Hogg & Bernier 2005, Lempriere et al. 2009). Boreal forest (CMI > 0) Parkland (CMI -15 to 0) Future Vegetation? Prairie (CMI < -15) Based on CGCM2 A21 scenario for Projected northward shift of prairie-like climates based on the CMI

9 Dry CMI Moist Impacts of the drought on aspen forests in western Canada The Climate Moisture Index (CMI) was used to assess temporal & spatial variation in moisture conditions (ANUSPLIN & BioSIM) long-term mean CMI Shows that the drought was especially severe in the areas showing massive dieback & mortality Mean CMI for 25 CIPHA sites in western Canada for 12-month periods ending 31 July of each given year Area showing severe aspen dieback & mortality CMI Drought ( ) 0 ANUSPLIN BioSIM DRY MOIST Climate Moisture Index (CMI) ANUSPLIN interpolation of CMI by D.T. Price, M. Siltanen & D. McKenney

10 Annual stem mortality (%) Impacts of the drought on aspen forests in western Canada The drought led to a 30% decrease in regional aspen growth & was the main cause of aspen dieback & mortality (Hogg et al. 2008, Can. J. For. Res.) Annual health assessments showed an increase in wood-boring insects which may have amplified & prolonged the drought s impact Average aspen mortality at 25 CIPHA sites (150 plots) Year Repeat photography of CIPHA plot (BAT 1-2) showing drought impact Sites included in the analysis of mortality

11 Scaling up drought impacts from plot to region Mortality was very patchy, so that CIPHA plot monitoring alone is not sufficient to characterize regional-scale impacts of the drought This challenge is being met through the inclusion of aerial surveys & a remote sensing component with networks of additional validation plots (Hall, Arsenault, Michaelian & others) Aspen mortality from 2004 aerial surveys in the area of severe drought (M. Michaelian) CIPHA plots Mortality level: Mortality level (%) Light Moderate Severe Mapping aspen mortality from Landsat imagery (Canopy Reflectance Model)

12 % Dead aspen mass ( ) The CMI as a predictor of drought-induced forest mortality up to 5 years in advance? 100 Dry Moist ` Long-term plots Validation plots Expon Climate Moisture Index ( ) y = e x R 2 = CIPHA site Validation plot Forested land Results showed relationship between the CMI and % dead aspen mass 4 years afterward Could provide a useful tool for guiding forest management practices & adaptation strategies

13 CMI Renewed concerns.. Since 2007, unprecedented droughts have recurred in Alberta & in northwestern Ontario 4 million ha gross area of aspen mortality west of Thunder Bay (Keizer, pers. comm). Major drought impact on Edmonton s urban forest (Lieffers article, Edmonton Journal) Threat to future forest health & regeneration in the boreal forest (esp. NE Alberta) 30 Climate Moisture Index Index Edmonton city centre Edmonton City Centre Year The ongoing Edmonton drought is one of the worst on record (keep your trees well-watered!) Need for near real-time detection, monitoring & assessment of drought & its direct/indirect impacts on Canada s forests

14 Current & potential linkages with the DRI Contributing to the forest impacts section of DRI theme I paper: - Hanesiuk et al., Physical Characterization of the Severe Canadian Prairie Drought Developing and applying simple drought indicators for assessing & predicting impacts on forest growth, dieback & mortality - Climate Moisture Index - Soil Moisture Index (method in development) - Opportunity to compare performance of drought indicators - Need for integrated, near real time reporting of drought conditions across sectors (e.g., agriculture, forestry, hydro-electric power)

15 Current & potential linkages with the DRI Multidisciplinary, multi-sector research questions: - How do regional droughts affect carbon & water cycling across complex landscapes e.g., the aspen parkland and boreal forest transition zone - Is drought severity affected by large-scale changes in forests? e.g., has massive forest die-off by mountain pine beetle in BC (past 10 yr) affected downwind humidity & rainfall patterns in the Prairie Provinces?? photo courtesy of Kevin Buxton, BC MFR mountain pine beetle damage in BC - Can we determine if anthropogenic climate change is already leading to increases in drought severity & impacts (at global and regional scales)?

16

17 CIPHA core team E.H. Ted Hogg (NoFC) James Brandt (CFS-HQ) Ron Hall (NoFC) Eric Arsenault (NoFC) Trisha Hook (NoFC) Tony Hopkin (GLFC) Al Keizer (GLFC) Bob Kochtubajda (EC) Michael Michaelian (NoFC) Research collaborations Alan Barr (EC) Pierre Bernier (LFC) Andy Black (UBC) Jag Bhatti (NoFC) Barry Cooke (NoFC) Werner Kurz (PFC) Juha Metsaranta (NoFC) Vic Lieffers (U of A) Dan MacIsaac (CFS-CWFC) Dan McKenney (GLFC) David Price (NoFC) Jan Volney (NoFC) and others Team members & collaborators Tree-ring analyses Trisha Hook Thierry Varem-Sanders and others Forest health crew leaders Mike Michaelian Trisha Hook Al Keizer Michael Salomons Roger Brett and others Aerial surveys & remote sensing systems Mike Michaelian Eric Arsenault Rob Skakun Field & laboratory assistance Jim Hammond Rick Hurdle Roger Nesdoly (MM) Brad Tomm Jim Weber Marc Berube Natacha Bissonnette Sarah Breen Laura Chittick Brian Christensen Andrea Durand Ray Fidler (PC) Michelle Filiatrault Cathryn Hale Funding (CIPHA study) Amy Irvine Angela Johnson Sarah Martin Ryan Raypold Erin Van Overloop Mark Schweitzer Dominic Senechal Jessica Snedden Joey Tanney Bill van Egteren Bryan Vroom Cedar Welsh Dave Wieder (PC) and many others Climate Change Action Fund Program of Energy Research and Development Mistik Management Ltd., Meadow Lake, Sask. Forest 2020 AAFC PFRA Administration Canadian Space Agency CFS-NRCan A-base funding