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 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 over 7 million acres converted back to forest Consequences –Plow pans –Soil compaction –Rooting restrictions Fries et al Background Continued

Steve Howell, 2000Brown 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 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 White Pine Decline: Hypotheses

Portland Wells Lebanon Hollis Limington Casco Nobleboro Oxford New Gloucester Massabesic 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 analysis Fries 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 cm Significantly 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 Diorama Fries 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, 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 19901%0% 19910% 19920% 19930% 19941%0% 19959%0% %67% % %0% 19992%0% 20001%0% 20012%0% Percent of dead trees sampled Peaked in Fries et al. 2002

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

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

1995 Standardized Stream Flows Station Yr. of Record MayJuneJulyAug.Sept.Oct. St. John (north) Mattawamkeag (north) Narraguagus (east) Saco (NH mt.) Carrabassett (mt.) Sandy (mt.) Little Androscoggin Sheepscot Oyster Fries et al Drought localized to southern Maine and far northern Maine

Climate Data Location of stream gauge stations and weather stations Fries et al. 2002

Other Considerations Biotic Stress Ips bark beetle Armillaria 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 – period for years of last growth – period of visual mortality Fries et al. 2002