Impacts & patterns of recent bark beetle outbreaks in the Southwest

Transcription

1 Impacts & patterns of recent bark beetle outbreaks in the Southwest Joel McMillin USDA Forest Service, Forest Health Protection Flagstaff, Arizona USFS Prescott NF

2 Pre-2000 ponderosa pine forests in SW M.R. Wagner, NAU

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4 Southern aspects, rocky slopes Apache-Sitgreaves National Forest, Arizona J. McMillin, USFS

5 Ponderosa pine piñon/juniper transition zones Coconino National Forest, Arizona J. McMillin, USFS

6 Poor site quality/high stand density March 6, 2002 Horsethief Basin - Prescott National Forest, AZ J. McMillin, USFS

7 August 21, 2002 Horsethief Basin - Prescott National Forest Arizona fivespined ips, Ips lecontei Horsethief Basin 1974 J. Schalau USFS R3 FHP J. McMillin, USFS

8 Acres impacted of ponderosa pine by bark beetles in Arizona, Acres 800, , , , , , , , Year USFS FHP Region 3

9 2003 Piñon mortality Coconino NF, AZ 7,127 pinyon ips collected in 1 trap in 1 week J. McMillin, USFS

10 2003 Piñon mortality near Santa Fe, NM R3 FHP, USFS

11 2003 Piñon 2004 Twig twig beetle damage damage on Laguna Hansen, Baja California San Juan NF, CO J. McMillin, USFS T. DeGomez, UA

12 Number of Trees (Millions) Piñon Mortality Estimated Number of Trees from FHP Aerial Detection Surveys Arizona California Colorado Nevada New Mexico Utah Year

13 Mixed conifer mortality Apache-Sitgreaves National Forest, Arizona J. McMillin, USFS

14 Recent true fir bark beetle activity in AZ & NM 100,000 90,000 80,000 70,000 Acres 60,000 50,000 40,000 30,000 20,000 10, Year

15 Recent Douglas-fir beetle activity in AZ & NM 90,000 80,000 70,000 60,000 Acres 50,000 40,000 30,000 20,000 10, Year

16 Patterns of tree mortality in ponderosa pine forests of Arizona M.R. Wagner, NAU

17 Roundheaded PB Mountain Pine Beetle High m Relative abundance of bark beetles attacking ponderosa pine by elevation in Arizona Pine engraver Southern PB Western PB AZ fivespined ips Sixspined ips Mid m Low m Williams et al Env. Ent. 37:

18 257: 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

19 Bark beetle impacts to ponderosa pine by National Forests in Arizona 25 Tonto Prescott A-S Coconino Percent Reduction Basal Area Trees/ha

20 Probability of ponderosa pine mortality by elevation and trees/hectare Probability tph Elevation (m) Trees * ha

21 Probability of ponderosa pine mortality by mean tree diameter (Prescott NF) Probability p Mean tree diameter all species (cm) 60 Mean tree diameter all species (cm)

22 Selection of dwarf mistletoe-infected ponderosa pine by Ips during drought Tonto National Forest Live Dead <1.6 >4.4 Average DMR Kenaley et al WNAN 63:

23 WJAF 23: (2008)

24 Hazard rating for western pine beetle % PP >85 (3) (2) <50 (1) Ave. PP DBH >12 (3) (2) <8 (1) Basal Area (ft 2 /ac) >120 (3) (2) <80 (1) Composite Stand Hazard Values Hazard Rating High Moderate Low

25 Hazard rating for Ips beetles during drought? Site index or elevation low (3) mid (2) high (1) + Ave. PP DBH <8 (3) 8-12 (2) >12 (1) + Tree density high (3) moderate (2) low (1) Stand DMR Stand Hazard high (3) high (10-12) + moderate (2) = moderate (7 9) low (1) low (4-6)

26 Factors associated with pine mortality Weather & Climate Stand & site Conditions Bark Beetle Population

27 Compared to pre-1900 forests, today s southwestern ponderosa pine forests are: Denser (35x) - more small trees - fewer large trees Increased drought impacts & Ips habitat Photos courtesy of Pete Fulé, NAU

28 Current drought is considerably warmer than two previous droughts in the last century (N. Cobb and others)

29 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

30 Bark beetle activity by PDSI on Prescott NF Acres impacted Acres impacted = PDSI = Palmer Drought Severity Index PDSI less than -3.0 seems to be threshold for significant beetle activity in pine forests of Arizona Ann Lynch (RMRS) & AZ FHP

31 2009 was 4th driest year on record in Flagstaff 11.65

32 3 rd largest snow storm last week in Flagstaff

33 Acres impacted vs. winter precipitation Infested acres in AZ statewide 700, , , , , , , y = x R 2 = 0.826, P = Winter precipitation (mm) Courtesy of M.R. Wagner, NAU

34 40.0 Generalized annual Arizona climate (Long-term averages for each day of the year) = Temp max = Precipitation 1.0 Seasonal drought -5.0 Jan July Dec Time of Year 0.0

35 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

36 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

37 Outbreaks in the future?