White Pine Decline in Maine

1
White Pine Decline in Maine

• M. Fries, W.H. Livingston
• Department of Forest Ecosystem Science
• University of Maine

• C. Granger, H. Trial, D. Struble
• Forest Health and Monitoring Division
• Maine Forest Service

S. Howell S.W. Cole Engineering, Inc.Bangor, ME
December 2002
2
Background

• Tree decline and mortality from 1997- 2000
• Southern Maine
• Scattered locations
• Simultaneous appearance
• Dense, pole-size stands

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Background Continued

• Field abandonment
• By 1940 total number of farms in Maine declined
  by 80
• From 1872-1995 over 7 million acres converted
  back to forest
• Consequences
• Plow pans
• Soil compaction
• Rooting restrictions

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Rooting Habits of White Pine

• White pine rooting depth inhibited by
• Plow pans
• Lithological discontinuity (abrupt texture change
  from fine to course)
• Shallow water table or bedrock

• White pine roots will grow deep if soil-structure
  inhibitors not present

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White Pine Decline Hypotheses

• Predisposition to drought stress
• Shallow rooting depth potential
• High stand densities
• Poor prior growth
• Drought prior to 1997 initiated decline

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Methods Sampling

• Paired sites in nine locations
• High mortality
• Low mortality

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Methods Sampling Site Design

• Modified Forest Health Monitoring (FHM)
• 4 adjacent circles
• Each 48 in diameter

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Summary of Methods for Evaluating Hypotheses

• Hypothesis - Shallow soil restrictions
  predisposed white pine to drought
• - Measure and characterize soil restrictions
• Hypothesis High stand density and poor prior
  growth also predispose white pine to drought
  damage - Compute stand density - Measure prior
  growth using tree ring analysis
• Hypothesis - Drought prior to 1997 initiated
  decline
• Examine climate data
• Ascertain year of last growth on dead trees using
  tree ring analysis

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Results

• Mortality
• High mortality
• 31 of stems
• Low mortality
• 2 of stems
• Significantly different
• Depth to rooting restriction
• High mortality
• 24.6 cm
• Low mortality
• 44.8 cm
• Significantly different

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Decline Associated with Shallow Soil
Restrictions (lt30cm)

• Plow pan (2 sites)
• Water table (1 site)
• Bedrock (1 site)
• Lithological discontinuity (5 sites, 3 with
  plow layer)

Harvard Forest Diorama
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High Mortality Plots Compared to Low Mortality
Plots

• Before mortality
• Smaller DBH
• More stems
• Initial BA similar
• After mortality
• understocked for size class
• density similar to low mortality plots

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Growth of Surviving Trees

• Number of years of declining growth, 1995-2000 in
  surviving trees did not differ between plot types
• High mortality sites 2.8
• Low mortality sites 2.4
• Growth trends in surviving trees in high and low
  mortality plots did not differ

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Prior Growth of Dead White Pine
Increment growth of dead vs. surviving trees at
Limington

• Period of reduced growth gt24 yrs (7 of 8 sites)
• Ages similar (43 vs 45 yrs)
• Smaller DBH (19 vs 25 cm)

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Year of Last Growth Increment
Last year of growth dead trees high mortality dead trees low mortality
1990 1 0
1991 0 0
1992 0 0
1993 0 0
1994 1 0
1995 9 0
1996 31 67
1997 33 33
1998 19 0
1999 2 0
2000 1 0
2001 2 0

• Percent of dead trees sampled
• Peaked in 1996-97

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Prior to 1997, 1995 Worst Drought Year
(Number of standard deviations from 89 yr mean)
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Drought Prior to 1997
Standardized Stream Flows Indicate Severe
Regional Drought in 1995
Year Little Androscoggin Little Androscoggin Oyster Oyster Sheepscot Sheepscot
AUG SEPT AUG SEPT AUG SEPT
1990 -1.4 -0.7 -0.8 -0.2 0.6 0.1
1991 -1.8 -0.5 -0.9 0.6 -2.1 0.0
1992 -0.2 -0.6 0.3 -0.5 -0.3 -0.6
1993 -1.5 -1.5 -1.1 -1.5 -0.9 -0.5
1994 -1.3 -1.2 -1.6 -0.8 -0.8 -1.3
1995 -2.8 -2.8 -1.7 -1.9 -2.1 -2.6
1996 -0.7 -1.0 -0.7 -0.8 0.0 0.1
1997 -1.1 -0.5 -1.3 -0.6 -0.8 -0.8
1998 -0.6 -1.1 -0.4 -0.8 -0.6 -1.0
1999 -1.3 -1.6 -3.2 -4.6 1.6 -1.7
2000 -0.2 -1.4 -0.6 -0.7 -0.5 -0.9
2001 -1.9 -2.2 -1.8 -1.4 -1.7 -1.3
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1995 Standardized Stream Flows
Drought localized to southern Maine and far
northern Maine
Station Yr. of Record May June July Aug. Sept. Oct.
St. John (north) 76 -0.8 -1.7 -1.9 -1.6 -2.0 -1.7
Mattawamkeag (north) 68 -0.7 -0.8 -1.7 -2.2 -2.3 -2.2
Narraguagus (east) 54 -1.2 -0.7 -0.9 -1.3 -1.3 -1.4
Saco (NH mt.) 99 -2.2 -1.5 -1.5 -1.4 -1.5 -1.4
Carrabassett (mt.) 100 -2.0 -1.5 -1.3 -1.4 -1.6 -1.3
Sandy (mt.) 74 -2.1 -1.5 -1.3 -1.6 -1.7 -1.4
Little Androscoggin 89 -2.0 -1.7 -2.1 -2.8 -2.8 -1.8
Sheepscot 72 -2.0 -0.4 -1.1 -2.1 -2.6 -1.4
Oyster 67 -2.1 -1.1 -1.3 -1.7 -1.9 -1.5
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Climate Data Location of stream gauge stations
and weather stations
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Other ConsiderationsBiotic Stress

• 88 trees sampled at DBH and roots
• Dominant
• Few needles, red needles, no needles
• of trees with pests
• 63.6 Cerambycidae
• 60.2 Ips spp.
• 56.8 Armillaria spp.
• All secondary in nature

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ConclusionsField Abandonment Created Conditions
Leading to White Pine Decline

• Plowing changed soil characteristics that
  predispose pine to decline
• Plow layer
• Lithological discontinuity
• Pine regenerated on sites to which it is not
  adapted
• High water table
• Shallow bedrock
• Mortality present where field abandoment was
  highest in south but not in north

Harvard Forest Diorama
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Additional Conclusions

• Density might be an additional predisposing
  factor
• Mortality thinned-out poorly growing trees
• Surviving trees growing normally
• Drought is the likely inciting stress in white
  pine decline
• 1995 year of severe drought in southern Maine
• 1995-1998 period for years of last growth
• 1997-2000 period of visual mortality

Steve Howell, 2000
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