Historic, Archive Document Do not assume content reflects current scientific knowledge, policies, or practices. Forest Health Report 11-03 March 2011 Reserve HEALTH OF WHITEBARK PINE FORESTS AFTER MOUNTAIN PINE BEETLE OUTBREAKS aSB608 .P65H42 SANDRA KEGLEY, FOREST ENTOMOLOGIST, JOHN SCHWANDT, FOREST PATHOLOGIST, 2011 COEUR D’ALENE, ID; KEN GIBSON, FOREST ENTOMOLOGIST, MISSOULA, MT (RETIRED); DANA PERKINS, ECOLOGIST, BLM, CHALLIS, ID ABSTRACT Whitebark pine (Pinus albicaulis), a keystone mature whitebark pine averaged 64 percent in high-elevation species, is currently at risk due to northern Idaho, western Montana, and the a combination of white pine blister rust (WPBR) Greater Yellowstone Area (GYA) (southwestern (Cronartium ribicola), forest succession, and Montana, eastern Idaho, and northwest outbreaks of mountain pine beetle (MPB) Wyoming) but only 4 percent in drier central (Dendroctonus ponderosae). While recent Idaho. Infection levels on whitebark pine mortality is often quantified by aerial detection regeneration ranged from 0 to 81 percent. surveys (ADS) or ground surveys, little Regeneration of other tree species, primarily information is presented to describe what stands subalpine fir (Abies lasiocarpa), outnumbered look like following MPB outbreaks. This whitebark pine in 69 percent of areas. Based on information may help prioritize areas for WPBR and MPB impacts on whitebark pine and restoration. In 2008 and 2009, the severity of abundance of other tree species, at least 57 MPB impacts was measured in 42 whitebark percent of sites surveyed will likely convert from pine stands in Idaho, Montana, and Wyoming. whitebark pine to other cover types without WPBR was recorded on remaining live, mature restoration efforts or wildfire. In central Idaho, whitebark pine and whitebark pine regeneration. current outbreak losses were compared to losses Probable stand trajectory was determined by from an outbreak that occurred circa the 1930s. comparing abundance and health of remaining In four of six stands attacked in both periods, whitebark pine with other competing tree more whitebark pine basal area was killed in the species. During the recent outbreak, 30 to 97 1930s. percent of whitebark pine basal area tallied within each stand was killed by MPB. The INTRODUCTION density of live whitebark pine dropped by more Whitebark pine (Pinus albicaulis) is a keystone than 80 percent on over half of areas surveyed. species of high elevation ecosystems throughout WPRBR infection levels on remaining live, western North America. It is often the only tree United States Forest Northern 200 East Broadway Department of Service P.O. Box 7669 Agriculture Missoula, MT 59807 species capable of surviving in harsh subalpine areas, and is crucial in watershed stabilization and creating habitats that support a wide diversity of plants and animals. Old gnarled relics in remote timberline areas provide important aesthetic values by creating high elevation vistas and providing much of the character of the alpine experience (Schwandt 2006, Tomback and others 2001). Whitebark pine is currently at risk in much of its natural range due to a combination of white pine blister rust (WPBR, Cronartium ribicola) (an introduced disease)(fig. 1); successional replacement by shade tolerant species (fig. 2), and recent outbreaks of mountain pine beetle Figure 2. Subalpine fir becoming dominant cover type (MPB, Dendroctonus ponderosae) (Keane and as whitebark pine is killed by mountain pine beetle at others 2002, Gibson and others 2008). Although Kings Hill, Lewis & Clark National Forest, Montana. MPB outbreaks have occurred historically in whitebark pine causing severe losses of mature Aerial detection surveys (ADS) have trees, the additional impacts of WPBR on documented recent increases in MPB activity in the Northern Rockies (Gibson 2004), but regeneration and cone production have caused population declines far exceeding previous levels coverage has not always been complete or consistent. In addition, surveys only record resulting in local extirpation of some populations recent mortality, so cumulative mortality is not and threatened extinction of others (Schwandt 2006). known if areas are not flown annually. Even where annual mortality levels have been reported, ADS does not document WPBR infection levels or the amount of live whitebark pine remaining to provide regeneration. Since whitebark pine depends almost exclusively on the Clark’s nutcracker (Nucifraga Columbiana) for natural regeneration (Tomback and Linhart 1990), the loss of most mature whitebark pines in a stand may result in little to no regeneration if there are too few cone-bearing trees to support a nutcracker population (McKinney and others 2009). There have been many reports documenting MPB mortality in lodgepole and whitebark pine stands during MPB outbreaks (Kegley and others 2001, 2004; Gibson 2004, 2005, 2007; Gibson and Aquino 2006; Gibson and others 2008, Macfarlane and others 2010), but these have usually been limited in scope, conducted before es ad § staaicetin the outbreak has run its course, or have not always looked at competing vegetation or Figure 1. Whitebark pine regeneration infected regeneration. Recent MPB outbreaks have with white pine blister rust. received a great deal of attention (Gibson 2004, Logan and Powell 2001) and have been prevalent across much of the whitebark pine range — In semiarid central Idaho, there were several especially in the Northern Rockies. However, stands where skeletal trees killed by MPB in an little information is presented to describe what outbreak circa the 1930s remained on site and the stands look like following MPB outbreaks were quantified and aged by tree ring analysis in except to claim the future prognosis for 1998 (Perkins and Roberts 2003). This whitebark pine is bleak (Tomback and others presented an opportunity to compare current 2001). outbreak losses with losses from the earlier outbreak (fig. 4). We investigated this information gap by documenting the condition of regeneration and remaining live, mature trees in various stand types following MPB outbreaks (fig. 3). We hope this information will help resource managers better understand losses from a combination of insect and disease agents and provide information that will assist in developing and prioritizing restoration activities. The primary goal of this project was to obtain information that could be used to make recommendations and set priorities regarding restoration of whitebark pine in the Northern Rockies. Specific objectives to meet this goal were to: 1. determine the severity of MPB impacts in whitebark pine stands following Figure 4. Current mountain pine beetle killed trees with red outbreaks and to quantify both dead and needles (circle) compared to trees killed during the 1930s remaining live, mature whitebark pine outbreak (pentagon) on Poverty Flat near Clayton in central Idaho. Trees killed during the 1930s outbreak are visible 2. determine WPBR status of remaining throughout the photo as gray snags with no fine limbs. mature, live whitebark pine 3. determine WPBR infection levels in whitebark pine regeneration 4. determine probable stand trajectory by METHODS recording health and abundance of other tree species in mixed stands Forests in Idaho, Montana, and Yellowstone National Park (YNP) in Wyoming where recent MPB outbreaks have occurred in whitebark pine were identified from past ADS, local specialists, or other surveys. Within these forests, we selected 42 stands on National Forest, Bureau of Land Management, YNP, and private lands. These stands were accessible by road or within reasonable hiking distance and had several years of MPB-caused tree mortality (fig. 5). Stands were sampled using variable-radius plots for : ee aa eee large trees and fixed-radius plots for cee ee ee ig. regeneration. Plots were taken at a frequency that 2 Gs Dee ee aN adequately sampled selected stands. From plot Figure 3. Stand evaluated near Avalanche Peak in center, a 10 or 20 basal area factor (BAF) prism Yellowstone National Park with 93% whitebark pine was used to select sample trees greater than five mortality following a recent mountain pine beetle outbreak. inches diameter at breast height (dbh). BAF was coordinates, slope, aspect, elevation, and slope chosen to get an average of 8 to 10 trees per plot. position. All trees less than five inches dbh and The same BAF was used for all plots in a given greater than six inches in height were tallied in a stand. Data collected for each tree included tree 1/300" acre regeneration subplot (radius = 6.8’) species, dbh, condition, and damage code at plot center of each variable-radius plot. (mortality causes and WPBR severity levels for Regeneration included seedlings and saplings live trees). Stand information included GPS from six inches tall to 4.9 inches dbh. RUM ‘> PYR Rust Infection on live WBP >5" dbh No infection es Light infection Moderate infection High infection MPB caused mortality (basal area) <50% mortality fe) Goeur d'Alene 50-79% mortality Y >/79% mortality Missoula e OAL @ _bozeman PPM@ Salmon @ McCall Sd Boise WYOMING e . Idaho Falls Legend a State boundaries County boundary major lakes National Forests Figure 5. Locations of 42 whitebark pine (WBP) stands surveyed in Idaho, Montana, and Wyoming with white pine blister rust infection levels and mountain pine beetle (MPB) caused mortality. Survey data were entered into a spreadsheet and impacts and tree composition by geographical analyzed using the Forest Insect and Disease locations. Tally (FINDIT) program (Bentz 2000). The following statistics were calculated for each In central Idaho, whitebark pine BA lost in the stand: current MPB outbreak was compared to BA lost 1. Total trees/acre (TPA) by species in the 1930s outbreak. 2. Total live and dead basal area (BA ft°/ac) 3. Quadratic mean diameter (QMD) of live RESULTS trees by species 4. Live stand density index (SDI) Mountain Pine Beetle Mortality 5. Number of dead and live trees 6. Percentage TPA of each tree species Mortality from MPB in the 42 stands surveyed 7. Percentage BA of each tree species ranged from 30 to 97 percent (mean 72 percent) 8. Percentage of BA killed by damaging of whitebark pine BA (fig. 6). Over 90 percent agents in 2009, 2008, and mortality older mortality occurred in eight stands in the than 2008 following locations: Sawtooth National 9. TPA by species in 1/300" acre Recreation Area (SNRA) in central Idaho, | regeneration plots Beaverhead-Deerlodge National Forests in the Tobacco Roots and Gravelly Ranges, Helena Multiple linear regression analysis and ANOVA National Forest in western Montana, Idaho were used to examine relatIionships between Panhandle National Forests in northern Idaho, slope, elevation, and aspect with basal area killed and YNP in Wyoming (highlighted in red in by MPB and amount of WPBR infection. We table 1). also analyzed differences in MPB and WPBR Whitebark Pine Basal Area after Mountain Pine Beetle Outbreaks in 42 Stands Oasis Lake (OAL) Kings Ridge (KHR)} Kings Hill (KHL) 4 Edith Lake fEDL) 4 Edith Peak (HEL} MorellRidge (MRLP} florellPeal (MARL +i Trout Lake (TRT} Pyramid Lake (PYL) r RussellRidge (RUM 8 eee } SylLvakae (nSL ) -R AAttSanmneeeeeeeeneeeeeneeem Avalanche Peak {AvPK) Dunraven Pass tDRP) fat. Washburn (MIT) Pick et Pin (PPI) lronMitn, (IRN) Eagle Creek (EAGL Bear Creek (BEAR) Lightning Lake (LILK} Litfle Bear (LB) Big oe Lower (BIGL) ig SkyU pper (BIG) Broomtail Ridge (BTR) @ Live WBP Black Butte (BB) Lazyman Hill (LMH) Wolverine Basin (WVB) w MPB killed WBP Strawberry Butte (STB) Queen's Hill (QH) CrystalLake (CRL) Clover Meadows (CLM) Sawtell Meadow (STta} Sawtell Peak (STP) Big Hill {BGH) Assout Basin (ASIN) Anderson Peak (AND) - Silver Peak (SIL) Gal. Summit-North (CRS) Salena Summit (AVL) Anderson Creek (ABE) Titus Lake Peak (TLK} Railroad Ridge (NRR} Railroad Ridge (RRB) [eeieeee Ineienee enmameatials 50 100e4 150 200 Ne o0 | 1 800 Square feet of basal areaper acre Figure 6. Basal area of live and mountain pine beetle killed whitebark pine by stand. Table 1. Whitebark pine (WBP) stand characteristics used to predict cover type conversion risk with critical levels highlighted (see discussion for color coding definitions). These characteristics include WBP BA killed by mountain pine beetle (WBP BA dead, % WBP BA killed) and white pine blister rust (WPBR) infection levels on live, mature WBP and WBP <5 inches dbh. High % WBP WBP | Other ha J \NBP_ | WPBR eects Region/ Area | Stand/Year surveyed BA Live | BA spp. after on live 2 BA to other (ft/acre) | dead | BA y outbreak | mature killed cover WBP Railroad Ridge 2008 | 31 | 124 | 3 | sow | 91% | 6% | 1008 |fr ames - ca) Railroad Ridge 2008 fe eee eee |5 % pcan[ se |o e Peaied Central [D/ Anderson Creek 2008 17o e ee Sawtooth of see| e se [ae ae NRA Galena Summit 2008 143 a ae Galena Sum-North 2008 Silver Peak 2008 19% | 41% oiat ) Sa Con ia aa Challis NF pete Dy eee GYA/ See eee Targhee NF |s awtelt Meadow 2008 | 82__| 63 | a1 | 43% | 67% | 53% | 14m | |C lover Meadows 2008 | 31 | 1 | 4 | 78% | som | sax | sam ||2 727%% GY A/ Pcowal ane2 09 [as |9 3 |a e| o e | rose [ae] | BVRD NF- Tobacco ae See Roots tee |e fue [orP ave[ ne |o ef e fe GaY A:/ Ramee {0 Poe owe bee bee igs yU p 2a08c alP SN NR Oro re |i | GYA/ Yellowstone BigSkyLover 200 | 2 |1 76 |1 6 |a | mm | s3m | oa | Club (private) [title Bear2 009 | os | a9| 33 | am | orm | 7e% | 3o% |2 39 | GY A/ Gallatin NF - feces —[—e foe Par we we bo West +a Cask 2a __JL 201 is| o s |o n I Toe [ue |2 [oye ecm ae eae ee tte Beartooth [isa | ss | 38 [ sow [| rem | 4am [|2 6%][ | GY A/ Dunraven Pass 2008 82 45% Re Yellowstone Avalanche Peak 2009 | 18 peep fas esa] ara ges NP Sylvan Lake 2009 AEA|8 7% | | 19m _| | cage _| North [D/ IPNF ce Ridhge e2008e Fa mere)r age -fPu amidlLaakke e 22008-09 Yaar | o4%_| SE 33% | [89% ee ee Trout LLaakek e 22000099 .00. | pepe |a 78e% | = Western MT/ Pomel ia Lolo NF oa a oe Morell Ridge 2008 | 74% | Picos |a a |6 8 ys | as Higll 2008 a oa 58% [soe [oie Poen |a es |Kk iinnggs s Ridggee 2200080 8 _| |6 3% _| W MT/ Crazy Mtns Gallatin NF Oasis Lake 2009 62% Whitebark pine density (BA) was reduced by White Pine Blister Rust more than 80 percent on over half of stands surveyed. Over 50 percent of whitebark pine BA Infection on Live, Mature Whitebark Pine was lost on 81 percent of stands and 76 percent There were a total of 2,473 whitebark pine of sites currently have less than 50 ft’/acre of live tallied, and slightly more than half were infected whitebark pine BA remaining. Although stands with WPBR. However, only 10 percent of all were purposely selected where the MPB trees had severe infections with top kill that outbreak had peaked, a few stands contained would affect cone production. Most infections current beetle attacks so losses in these stands (54 percent) tallied were branch cankers, and are likely to increase. severity was light. We found no statistically significant There was a significant negative correlation relationships between geographic area, slope, between percent of trees infected with WPBR elevation, or aspect and basal area killed by and elevation (p<.001); infection levels increased MPB. as elevation declined. There were no statistically significant relationships between WPBR 1930s outbreak compared to current outbreak infection level and either slope or aspect. Of six stands in central Idaho where MPB outbreaks occurred in both the 1930s and 2000s WPBR infection levels within the 42 sampled time periods, three had significantly more BA stands ranged from 0 to 100 percent (Table 1). killed in the 1930s, two had approximately the Stands were grouped into 12 general locations same amount of BA killed during both periods, (fig. 8). The average WPBR infection level on and one had more BA killed in the current remaining live, mature whitebark pines in the outbreak (fig. 7). For some susceptible stands in Helena and Lewis & Clark locations in Montana central Idaho, this provides evidence that was over 80 percent, and in four other locations whitebark pine mortality during the 1930s MPB the average rust infection was over 60 percent. outbreak was as great as, or greater than, current The Sawtooth and Salmon stands in central mortality levels. Idaho consistently had low average rust infections (0 tol6 percent), while infection levels in other areas varied hitebark Pine Basal Area Killed by Mountain Pine Beetle widely. For example, three of four 140 ~\ pit bai antl x. sites in YNP in Wyoming varied from a OBA killed 1930s | 12 percent to 28 percent while the Mt. 120 wBAkilled 2000s Washburn site had an infection level of nearly 43 percent. Similarly, three Rhi =)o of four West Gallatin Montana sites had infection levels from 60 to78 80 percent, but Lightning Lake was only 37 percent. The Sawtooth and Salmon blister rust infection levels were significantly lower (p<.01) than (aBApfcaretrser2eaa )l most other locations. Blister rust levels at YNP were not statistically different than Salmon or Targhee but were significantly lower than all other locations (p<.05). Anderson Big Hill Silver Peak = Twin Peaks Titus Lake Avalanche Peak Peak Figure 7. Whitebark pine basal area killed in current and historic outbreaks in 6 stands in central Idaho. Percent White Pine Blister Rust on Mature Whitebark Pine | 100 80 70 60 50 40 - i%ntfreecetesd 20 10 aS oD oO om wv o ° se ~aS Fi re S&s g SS x < oFo w & x we of & <2 Figure 8. Percent of mature trees infected with white pine blister rust on 12 forests or areas. Number of stands sampled in each area is in parentheses. Infection on Live Whitebark Regeneration (Pinus contorta), Engelmann spruce (Picea Only 26 of 42 sites tallied sufficient numbers of engelmannii), and Douglas-fir (Pseudotsuga whitebark pine regeneration to get an estimate of menziesil). WPBR infection (table 1) (Only five sites tallied enough regeneration on the 1/300 ac. subplots, Regeneration the rest were determined by off-plot tallies). Tree species other than whitebark pine less than Average infection level on these 26 sites was 23 five inches in diameter were more prevalent on percent and ranged from 0 percent to over 80 28 (69 percent) of the 42 areas surveyed (fig.9). percent. The lowest average rust infection levels By far, the most abundant other species was were 1n central Idaho (0 to 5.3 percent). Infection subalpine fir (nearly 97 percent of all other levels of regeneration in northern Idaho varied species tallied). Other species recorded were from 15 percent to 23 percent. Those in western Englemann spruce, Douglas-fir, and lodgepole Montana ranged from 6.1 percent to 67.9 pine. Regeneration per acre of other species percent, and those in the GYA varied from 4.2 varied from O percent at Railroad Ridge in the percent to 80.8 percent. SNRA to 100 percent at Sylvan Lake in YNP. Twenty-three sites had more than 500 TPA of Competing Vegetation other species, and 13 of these sites had over 1000 Mature Tree Species Abundance TPA of other species. There were 18 stands with The abundance of other mature tree species more than 500 whitebark pine regeneration TPA, outnumbered live, mature whitebark pine after and four of these had more than 1000 TPA. The MPB outbreaks in 18 of the 42 stands surveyed. maximum TPA (3,000) of whitebark pine This represented 90 percent of sites in northern regeneration was recorded at Edith Lake (Helena Idaho and western Montana, 32 percent of sites NF) in western Montana. in the GYA, and 20 percent of sites in central Idaho. Subalpine fir (Abies lasiocarpa) was the most abundant mature tree species on 71 percent of sites surveyed followed by lodgepole pine