Impacts & patterns of recent bark beetle outbreaks in the Southwest
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Impacts & patterns of recent bark beetle outbreaks in the Southwest Joel McMillin USDA Forest Service, Forest Health Protection Flagstaff, Arizona USFS Prescott NF Pre-2000 ponderosa pine forests in SW M.R. Wagner, NAU Southern aspects, rocky slopes Apache-Sitgreaves National Forest, Arizona J. McMillin, USFS Ponderosa pine – piñon/juniper transition zones Coconino National Forest, Arizona J. McMillin, USFS Poor site quality/high stand density March 6, 2002 Horsethief Basin - Prescott National Forest, AZ J. McMillin, USFS August 21, 2002 Horsethief Basin - Prescott National Forest Arizona fivespined ips, Ips lecontei Horsethief Basin 1974 J. Schalau USFS R3 FHP J. McMillin, USFS Year 20 06 20 05 20 04 20 03 20 02 20 01 20 00 19 99 19 98 19 97 19 96 800,000 700,000 600,000 500,000 400,000 300,000 200,000 100,000 0 19 95 Acres Acres impacted of ponderosa pine by bark beetles in Arizona, 1995-2006 USFS FHP Region 3 2003 Piñon mortality Coconino NF, AZ 7,127 pinyon ips collected in 1 trap in 1 week J. McMillin, USFS 2003 Piñon mortality near Santa Fe, NM R3 FHP, USFS 2004 Twig damage 2003 Piñon twigbeetle beetle damage on Laguna Hansen, Baja California San Juan NF, CO T. DeGomez, UA J. McMillin, USFS Piñon Mortality 2001 - 2005 Estimated Number of Trees from FHP Aerial Detection Surveys 50 Arizona California Colorado Nevada New Mexico Utah 45 Number of Trees (Millions) 40 35 30 25 20 15 10 5 0 2001 2002 2003 Year 2004 2005 Mixed conifer mortality - 2004 Apache-Sitgreaves National Forest, Arizona J. McMillin, USFS Recent true fir bark beetle activity in AZ & NM 100,000 90,000 80,000 Acres 70,000 60,000 50,000 40,000 30,000 20,000 10,000 0 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 Year Recent Douglas-fir beetle activity in AZ & NM 90,000 80,000 70,000 Acres 60,000 50,000 40,000 30,000 20,000 10,000 0 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 Year Patterns of tree mortality in ponderosa pine forests of Arizona M.R. Wagner, NAU High 2510 – 2670 m Western PB Southern PB Pine engraver Roundheaded PB Mountain Pine Beetle Relative abundance of bark beetles attacking ponderosa pine by elevation in Arizona Mid 2060 – 2210 m AZ fivespined ips Sixspined ips Williams et al. 2008. Env. Ent. 37: 94-109 Low 1600 – 1750 m 257: 1353–1362 • FHM EM funded study – objectives: • Quantify stand level impacts of bark beetles on ponderosa pine forests in Arizona • Determine correlations between stand conditions & site characteristics and pine mortality • Extensive network of plots (1,100+) distributed across National Forests in Arizona Bark beetle impacts to ponderosa pine by National Forests in Arizona Tonto Prescott A-S Coconino Percent Reduction 25 20 15 10 5 0 Basal Area Trees/ha Probability of ponderosa pine mortality by elevation and trees/hectare 0.8 Probability 0.6 0.4 Elevation (m) 0.2 1800 1846 2200 2154 2600 2462 2769 3000 0.0 247 370.5 494 617.5 741 864.5 988 1111.5 1235 1358.5 1482 1605.5 1729 -1 250 Trees * ha tph 1700 Probability of ponderosa pine mortality by mean tree diameter (Prescott NF) 0.7 0.6 Probability p 0.5 0.4 0.3 0.2 0.1 12.715.217.820.322.925.427.930.5 33 35.638.140.643.245.748.350.853.355.9 12 MeanMean tree diameter all species (cm) tree diameter all species (cm) 60 Selection of dwarf mistletoe-infected ponderosa pine by Ips during drought Tonto National Forest Live <1.6 Dead >4.4 Average DMR Kenaley et al. 2006. WNAN 63: 279 - 284 WJAF 23: 113-120 (2008) Hazard rating for western pine beetle % PP >85 50-85 <50 Ave. PP DBH Basal Area (3) >12 (3) >120 (2) + 8-12 (2) + 80-120 (1) <8 (1) <80 Composite Stand Hazard Values 8–9 5–7 3–4 Hazard Rating High Moderate Low (ft2/ac) (3) (2) (1) Hazard rating for Ips beetles during drought? Site index or Ave. PP DBH Tree density elevation <8 (3) high (3) low (3) + 8-12 + moderate (2) (2) mid (2) >12 (1) low (1) high (1) Stand DMR high (3) + moderate (2) low (1) = Stand Hazard high (10 - 12) moderate (7 – 9) low (4 - 6) Factors associated with pine mortality Weather & Climate Stand & site Conditions Bark Beetle Population Compared to pre-1900 forests, today’s southwestern ponderosa pine forests are: 1909 2000 - Denser (35x) - more small trees - fewer large trees Increased drought impacts & Ips habitat Photos courtesy of Pete Fulé, NAU Current drought is considerably warmer than two previous droughts in the last century (N. Cobb and others) Increased temperatures affect host tree and bark beetles • Increased host tree stress? • Increased generations for bark beetles? High High Mid Mid Low Low Arizona fivespined ips Roundhead pine beetle Bark beetle activity by PDSI on Prescott NF 10 100000 PDSI = 80000 Acres impacted 8 6 70000 60000 4 50000 2 40000 0 30000 -2 20000 -4 10000 0 1890 -6 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 PDSI less than -3.0 seems to be threshold for significant beetle activity in pine forests of Arizona Ann Lynch (RMRS) & AZ FHP Palmer Drought Severity Index Acres impacted = 90000 2009 was 4th driest year on record in Flagstaff 11.65 3rd largest snow storm last week in Flagstaff Infested acres in AZ statewide Acres impacted vs. winter precipitation 700,000 y = -3588.8x + 703791 R2 = 0.826, P = 0.033 2002 600,000 500,000 2003 400,000 300,000 200,000 2001 100,000 1994 2000 0 0 50 100 150 200 250 Winter precipitation (mm) Courtesy of M.R. Wagner, NAU Generalized annual Arizona climate (Long-term averages for each day of the year) 40.0 = Temp max 1.0 = Precipitation Seasonal drought 0.0 -5.0 Jan July Time of Year Dec Conclusions from Arizona studies • Pine mortality follows elevational/site quality gradient • Tree or stand density (tree/ha or SDI) is also important • Dwarf mistletoe × bark beetle interactions are important • Implications for forest management Overall Conclusions • Outbreaks in the past Bark beetle-caused pine mortality occurred historically (obviously) – drought driven However, magnitude of outbreaks was less due to lower tree and stand density • Outbreaks in the present Increased probability of landscape level outbreaks with associated high trees/acre killed Increased white fir and Douglas-fir has led to increase of fir engraver & Douglas-fir beetle Outbreaks in the future?
