Mpbep 2011 04 prsnttn ecologicalimpactsmpbpineforestssouthernfoothills

Ecological Impacts of the Mountain Pine Beetle on Pine Forests of the Southern Foothills, Alberta A Case Study in Waterton Lakes National Park

Jodi Axelson (University of Victoria, Department of Geography, Victoria BC)

Background • Over the last decade researchers at the Pacific Forestry Centre have conducted a number of studies in lodgepole pine stands in BC and Alberta to examine the effects of the mountain pine beetle (MPB) on stand dynamics.

• Results of these studies have been used in decision support models such as TASS: Tree and Stand Simulator • In 2008/09 did dendroecological research in the westcentral Foothills as part of the Foothills Growth and Yield project “Monitoring and Decision Support for Forest Management in a Mountain Pine Beetle Environment” (Alfaro et al. 2009).

Waterton Lakes National Park • In 1981 permanent sample plots (PSPs) were established in five stands in Waterton Lakes National Park to study effects of the 1970s MPB outbreak.

• In 2002 stands were re-measured to evaluate the affect of the outbreak on stand dynamics.

• In 2010 stands were once again re-measured

project to fill a key regional gap in the southern Rocky Mountains. In addition, detailed dendroecological samples collected to determine the disturbance history at each stand.

East Slopes sites

Objectives • Develop ecological baselines of biotic disturbances in Waterton Lakes National Park using a dendroecological approach → reconstructing past MPB outbreaks and the mortality and regeneration dynamics post-disturbance

• Examine how biotic disturbances affect future forest structure and composition → overstorey, understorey and fuels • Integrate dendroecological data collected in this project with previous surveys in the central and northern Rocky Mountains to provide a comprehensive picture of disturbance regimes ands stand dynamics for the east slopes

PSP methods • Variable radius plots were used to measure overstorey metrics with a 2 m2/ha BAF prism (all years) • Fixed area plots were established to tally advance regeneration and seedlings by height class and species (2002, 2010) • Coarse and fine fuels were measured along 30 metre transects (2002, 2010)

Dendroecological methods • In 2010 dendroecological samples were collected from overstorey, understorey and CWD

Results • The degree of lodgepole pine mortality was highly variable between plots and between stands • Lodgepole pine density has decreased in all stands from 1981 to 2010 • Lodgepole pine volume decreased in all stands from 1981 to 2010, with exception of stand 1

Overstorey lodgepole pine density Stand No.

1981 (sph)

Pl - % Live (% Dead)

2002 (sph)

Pl - % Live (% Dead)

2010 (sph)

Pl - % Live (% Dead)

1 2 3

1393 1180 1523

90 (10) 45 (55) 68 (32)

1203 727 765

72 (28) 39 (61) 60 (40)

1029 361 482

84 (16) 76 (24) 67 (33)

4

724

7 (93)

174

35 (65)

78

49 (51)

5

1163

71 (29)

739

65 (35)

487

80 (20)

Average

1197

56 (44)

721

54 (46)

487

71 (29)

Lodgepole pine mortality 1981 1600 Dead Pl Live Pl

1400

Total trees/ha

1200

1000

800

600

400

200

0 1

2

3

Stand No.

4

5

Overstorey lodgepole pine density 1600

1981 2002 2010

1400

Total trees/ha

1200

1000

800

600

400

200

0 1

2

3

Stand No.

4

5

Overstorey lodgepole pine volume

Stand No. 1 2 3 4 5 Average

(m /ha)

Pl - % Live (% Dead)

123.74 201.62 222.42 148.19 171.01 173.39

83 (17) 32 (68) 56 (44) 5 (95) 61 (39) 47 (53)

1981 3

(m /ha)

Pl - % Live (% Dead)

(m /ha)

Pl - % Live (% Dead)

132.95 130.34 155.23 26.71 132.62 115.5

78 (22) 50 (50) 80 (20) 30 (70) 78 (22) 63 (37)

133.92 86.96 77.60 14.17 71.81 76.89

0.89 (0.11) 0.78 (0.22) 0.77 (0.23) 0.50 (0.50) 0.85 (0.15) 75 (25)

2002 3

2010 3

Overstorey lodgepole pine volume

Results • While there has been a decline in lodgepole pine density there has been an increase in non-host species such as spruce and fir from 1981 to 2010

• With the exception of stand 1, sapling and seedling densities have increased in all stands from 2002 to 2010 – High degree of variability in stocking between stands – Composition made up almost entirely of shade tolerant species

Overstorey

Saplings

Regeneration

Saplings

Regeneration

Saplings

Regeneration

Saplings

Regeneration

Results • Fine fuels have remained relatively constant between 2002 and 2010 – Stand 2 had increase as standing dead decreased by 32% between 2002 and 2010

• Coarse fuel mass and volume has increased in all stands from 2002 to 2010 as MPB killed trees have fallen to the ground

Fuels: Mass and Volume

Disturbance History • Overstorey pine ages ranged from 83 to 125 years old, and non-host species ranged between 51 to 104 years old • MPB was detected in all PSPs via stand-wide growth releases in the survivors (co-dominant and intermediate at time of attack) • Growth release data is supported by death dates for CWD and lagged regeneration pulses

Tree-ring data integration

Tree-ring data integration • Have collected a total of 28 lodgepole pine chronologies on the east slopes • Chronologies represent sites spanning 5 degrees of latitude – West-central region:15 chronologies – South-western region:11 chronologies

• Objective of studies was to evaluate mountain pine beetle (MPB) impacts on lodgepole pine

Research questions •

How homogenous is tree-ring variability along a north-south transect on the east slopes of the Rocky Mountains in Alberta?

•

How sensitive is tree-ring variability to stand disturbances (e.g., mountain pine beetle outbreaks) versus climate and/or climatic teleconnections?

•

Do chronologies from southern Alberta, in areas of known mountain pine beetle outbreak, group with chronologies collected farther north where there are no documented outbreaks?

Factor Analysis Factor

Eigenvalue

1 2 3 4

7.41 4.81 3.18 2.26

Percent total variance 28.5 18.5 12.2 8.7

Cumulative percent 28.5 47.0 59.2 67.9

FC1

FC4 FC2

FC3

Factor chronologies (FCs) FC1 loaded by low elevation Grande Prairie chronologies in Lower Foothills natural sub-region.

FC2 loaded by high elevation chronologies in Nordegg and Banff area in Subalpine natural sub-region.

FC3 based on two Waterton Lakes NP chronologies in the Montane natural sub-region at mid-elevation.

FC4 loaded by two Jasper NP chronologies also in mid-elevation Montane natural su-region.

Factor chronology 2 (Nordegg-Banff) The Pacific Decadal Oscillation and FC2 3 March PDO FC2

r = 0.56

2

Standardized Index

1

0

-1

-2

-3 1910

1920

1930

1940

1950

1960

1970

1980

1990

2000

Inferences •

Strong geographical and sub-regional groupings

•

Variance was spread amongst each retained FC

•

Some factors chronologies had strong correlations to climatic variables and/or climatic indices, whereas others had weak correlations with climate but strong regime shifts possibly indicative of stand disturbance dynamics

•

Chronologies in the west-central region did not group with chronologies in the south with documented MPB outbreaks, suggesting that disturbances detected arise from other agents

Take Home Messages • Stands in Waterton Lakes National Park show remarkable resilience • Thirty years post-MPB outbreak and stands are more heterogeneous • In face of uncertainty managers can use this type of information in a more natural disturbances based management framework

Acknowledgements

Questions?