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

Background

• Tree decline and mortality from 1997- 2000

• Southern Maine– Scattered locations– Simultaneous

appearance

• Dense, pole-size stands

Fries et al. 2002

• 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

Fries et al. 2002

Background Continued

Steve Howell, 2000 Brown and Lacate, 1961

• 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

Fries et al. 2002

Rooting Habits of White Pine

• Predisposition to drought stress– Shallow rooting depth

potential– High stand densities– Poor prior growth

• Drought prior to 1997 initiated decline

Fries et al. 2002

White Pine Decline: Hypotheses

Portland

WellsWells

LebanonLebanon

HollisHollis

LimingtonLimington

CascoCasco

NobleboroNobleboroOxfordOxford

New GloucesterNew Gloucester

MassabesicMassabesic

Methods: Sampling

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

Fries et al. 2002

48 ft

Methods: Sampling Site Design

•Modified Forest Health Monitoring (FHM)

- 4 adjacent circles- Each 48’ in diameter

Fries et al. 2002

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 analysisFries et al. 2002

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 cmSignificantly different

Fries et al. 2002

• Plow pan (2 sites)• Water table (1 site)• Bedrock (1 site)• Lithological

discontinuity (5 sites, 3 with plow layer)

Decline Associated with Shallow Soil Restrictions

(<30cm)

Harvard Forest DioramaFries et al. 2002

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

(Philbrook et al 1979)

Fries et al. 2002

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

Fries et al. 2002

Prior Growth of Dead White Pine

• Period of reduced growth >24 yrs (7 of 8 sites)

• Ages similar (43 vs 45 yrs)

• Smaller DBH (19 vs 25 cm)

Legend

O – Dead trees (n=29)

- Surviving Trees (n=13)

I – Standard Error

Increment growth of dead vs. surviving trees at Limington

Fries et al. 2002

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

Fries et al. 2002

Prior to 1997, 1995 Worst Drought Year

Standardized Stream Flows for Little Androscogin

-4

-3

-2

-1

0

1

2

3

May June July Aug. Sept. Oct.

Month

Sta

nd

ard

ized

Str

eam

Flo

w

1949

1978

1995

(Number of standard deviations from 89 yr mean)

Fries et al. 2002

Drought Prior to 1997

Year Little Androscoggin Oyster SheepscotAUG 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 -2.61996 -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

Standardized Stream Flows Indicate Severe Regional Drought in 1995

Fries et al. 2002

1995 Standardized Stream Flows

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

Fries et al. 2002

Drought localized to southern Maine and far northern Maine

Climate Data Location of stream gauge stations and weather stations

Fries et al. 2002

Other ConsiderationsBiotic Stress

Ips bark beetleArmillaria

root rot

• 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

Fries et al. 2002

• 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

Conclusions:

Field Abandonment Created Conditions Leading to White Pine Decline

Harvard Forest Diorama

Fries et al. 2002

Additional Conclusions

Steve Howell, 2000

• 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

mortalityFries et al. 2002