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White Pine Decline in Maine

White Pine Decline in Maine. C. Granger, H. Trial, D. Struble Forest Health and Monitoring Division Maine Forest Service. M. Fries, W.H. Livingston Department of Forest Ecosystem Science University of Maine. S. Howell S.W. Cole Engineering, Inc. Bangor, ME. December 2002. Background.

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White Pine Decline in Maine

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  1. White Pine Decline in Maine • C. Granger, H. Trial, D. Struble • Forest Health and Monitoring Division • Maine Forest Service M. Fries, W.H. Livingston Department of Forest Ecosystem Science University of Maine • 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 Fries et al. 2002

  3. 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 Fries et al. 2002

  4. Rooting Habits of White Pine 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

  5. White Pine Decline: Hypotheses • Predisposition to drought stress • Shallow rooting depth potential • High stand densities • Poor prior growth • Drought prior to 1997 initiated decline Fries et al. 2002

  6. Oxford Nobleboro Casco New Gloucester Limington Portland Hollis Lebanon Massabesic Wells Methods: Sampling • Paired sites in nine locations • High mortality • Low mortality Fries et al. 2002

  7. Methods: Sampling Site Design 48 ft • Modified Forest Health Monitoring (FHM) • 4 adjacent circles • Each 48’ in diameter Fries et al. 2002

  8. 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 Summary of Methods for Evaluating Hypotheses Fries et al. 2002

  9. 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 Fries et al. 2002

  10. Decline Associated with Shallow Soil Restrictions(<30cm) • Plow pan (2 sites) • Water table (1 site) • Bedrock (1 site) • Lithological discontinuity (5 sites, 3 with plow layer) Harvard Forest Diorama Fries et al. 2002

  11. (Philbrook et al 1979) 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 Fries et al. 2002

  12. 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

  13. Legend O – Dead trees (n=29) - Surviving Trees (n=13) I – Standard Error Prior Growth of Dead White Pine Increment growth of dead vs. surviving trees at Limington • Period of reduced growth >24 yrs (7 of 8 sites) • Ages similar (43 vs 45 yrs) • Smaller DBH (19 vs 25 cm) Fries et al. 2002

  14. Year of Last Growth Increment • Percent of dead trees sampled • Peaked in 1996-97 Fries et al. 2002

  15. Prior to 1997, 1995 Worst Drought Year (Number of standard deviations from 89 yr mean) Fries et al. 2002

  16. Standardized Stream Flows Indicate Severe Regional Drought in 1995 Drought Prior to 1997 Fries et al. 2002

  17. 1995 Standardized Stream Flows Drought localized to southern Maine and far northern Maine Fries et al. 2002

  18. Climate DataLocation of stream gauge stations and weather stations Fries et al. 2002

  19. Armillaria root rot Ips bark beetle 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 Fries et al. 2002

  20. Conclusions:Field 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 Fries et al. 2002

  21. 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 Fries et al. 2002

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