Blister Rust Alters Whitebark - PowerPoint Presentation

Slide1

Blister Rust Alters

Whitebark Pine Ecology at Treeline: Implications for Treeline Response to Climate Change

1University of Colorado Denver2Virginia Tech University3University of Iowa

Whitebark Pine Ecosystem Foundation, Whitebark Pine Science and Management Workshop, September 19, Coeur d’Alene, Idaho

Diana

F. Tomback,

1

Lynn M.

Resler,

2

George P. Malanson,

3

Emily

K.

Smith-McKenna,

2

Sarah

C. Blakeslee,

1

Jill

C.

Pyatt

1

, and Aaron C. Wagner

1

Slide2

Treeline

environmentsTreeline environments are climatically harsh.Soils are often nutrient-poor and unstable.Facilitation between plant species, or a “nurse” object and a plant, may improve plant survival (e.g., Callaway et al. 2002, Brooker et al. 2007).These same processes are essential at the upper treeline limit, enabling communities to respond to climate warming.

Slide3

Whitebark

Pine (Pinus albicaulis) at Treeline

Whitebark pine inhabits upper the subalpine and treeline zone throughout its distribution.It provides important ecosystem services and functions.Seeds dispersed to treeline by Clark’s nutcrackers.In the alpine–treeline ecotone (ATE), there is a mix of solitary

krummholz trees and tree islands composed of two or more krummholz trees.Tree islands form when a solitary tree becomes established, and other trees establish leeward.

Slide4

Tree establishment often occurs in protected locations leeward of:

nurse objectsnurse plantsin microtopography, Lee of Salix

‘Steps and risers’

Slide5

White pine blister rust

and treeline dynamicsIn some Rocky Mountain communities, whitebark pine is an important nurse tree and tree island initiator.Most common forest associates are subalpine fir (Abies lasiocarpa) and Engelmann spruce (Picea engelmannii).White pine blister rust (pathogen = Cronartium ribicola) is present in all treeline communities examined.Whitebark pine mortality disrupts its role as a tree island initiator. This Impacts community development at and above treeline.Will declines in whitebark

pine alter treeline community response to climate warming?

Slide6

Where is

whitebark pine a tree island initiator?Major initiatorStudy location

Lat. NStandley Glacier, Kootenay NP, BC51˚ 11'

Lee Ridge, Glacier NP, MT48˚ 55'

Divide/White Calf Mountains, Glacier NP, MT

48˚ 40'Line Creek RNA, Custer NF, MT

45˚ 02'

Not major initiator

Willmore

Wilderness Park, AB

53˚ 46'

Parker Ridge, Banff NP, AB

52˚ 10'

Gibbon Pass, Banff N P, AB

51˚ 11'

Tibb's

Butte, Shoshone NF, MT

44˚ 56'

Resler

et al. 2014,

Tomback

et al. 2014,

Tomback

and

Resler

, in prep

Slide7

Why is

whitebark pine a majority tree island initiator in some areas?HypothesisWhitebark pine’s prevalence as a tree island initiator is correlated to its relative abundance as a solitary tree.

Slide8

Is

whitebark pine’s prevalence as a tree island initiator proportional to its relative abundance as a solitary tree? NO. But it is generally abundant. Tomback et al. 2014, Resler et al. 2013; Tomback & Resler in prep.

Slide9

Regression analysis

Spearman rank correlation: 0.2619, n = 8, P = 0.501

Slide10

Why is

whitebark pine so abundant within climatically harsh treeline communities?Hypothesis: Whitebark pine has greater hardiness under harsh treeline conditions:We compared hardiness among whitebark pine, Engelmann spruce, and subalpine fir. We defined hardiness in three ways:Qualitative assessment of vigor.Requirements for a protective microsite.Annual shoot length, reflecting carbon acquisition and allocation.

Slide11

Primary study areas

Research from 2006 through 2014.Divide/White Calf Mountains--Glacier National Park and Blackfeet Tribal Land, MT--elevation ca. 2,200 m. Line Creek Research Natural Area, Custer National Forest, Beartooth Plateau, MT--elevation ca. 2,950 m.

Slide12

Relative hardiness

1) Qualitative assessment of vigor (1 to 4 = best), based on: windward needle death, condition of new shoots, and needle color.Divide Mtn.—Whitebark pine had significantly higher vigor than both fir and spruce (Kruskal-Wallis, χ2 = 18.9, df = 2, P = 7.8e-5, post hoc W = 19557, P = 0.037,post hoc, W = 13026.5, P = 2.08e-5)

Line Creek—No differences.2) Association of solitary trees with a protective microsite.At both Divide Mtn. and Line Creek, fewer whitebark pine were associated with a protective microsite than fir or spruce.(χ2 = 9.769, df = 2, P = 0.008, χ2 = 11.3217, df = 2, P = 0.003) Blakeslee et al., 2012, MS.

Slide13

Shoot lengths—bootstrapped 95%

confidence intervals (Blakeslee et al. in prep., Wagner) Whitebark PineSubalpine FirEngelmann SpruceDivide Mountain

171515Line Creek RNA211220

Slide14

Why is

whitebark pine a majority tree island initiator?HypothesesWhitebark pine offers greater microsite protection than other conifer species.

Slide15

Does

whitebark pine offer better leeward protection than associated conifers?Measured 11 biophysical variables leeward of four common treeline microsites: whitebark pine, Engelmann spruce, rock, and unprotected microsite. Air & soil temp., soil moisture, wind speed & gusts, PAR.Soil for total carbon and nitrogen; leeward sky exposure. Pyatt 2013; Pyatt et al, MS.

Slide16

Microclimate and microsite: summary

Compared to rock and open microsites, leeward conifer microsites had more favorable microclimates:

Reduced maximum air and soil temperatures.Higher minimum soil temperatures.Lower PAR.Reduced wind and gust speeds. Whitebark pine microsites and spruce microsites offered similarly protective microclimates.

No statistical difference in soil C and N.BUT, whitebark pine had significantly lower sky exposure in leeward microsites in comparison with subalpine fir, rock, and open sites (Boggs, Bevency Kruskall-Wallis, n = 8, R = 48.61, P =0.000).

Slide17

Whitebark

pine offers leeward protectionPyatt 2013

Slide18

Is facilitation really occurring?

Simulating the impact of blister rustIn 2010, we selected 22 control and 22 experimental dyads on Divide/White Calf Mtn.Dyad = windward whitebark pine; leeward spruce or fir.We girdled and defoliated the experimental windward whitebark pine in 2010. Note: all experimental whitebark pine were infected by blister rust. We measured shoot lengths on leeward conifers in 2010, 2011, and 2012.Blakeslee 2012; Blakeslee et al. MS.

Slide19

Leeward conifer shoot

lengths—bootstrapped 95% confidence intervals (Blakeslee et al. MS., Wagner)

Slide20

Is facilitation occurring?

seeds and seedlings We examined survival rates of planted seedlings and the germination rates of sown seeds among four leeward microsites: whitebark pine, spruce, rock, and open.Divide Mtn.—sowed spruce seeds and planted fir seedlings.Line Creek—sowed spruce seeds and planted spruce seedlings.20 replicates for each microsite type for seedlings and for seeds.(Blakeslee 2012; Blakeslee et al. in prep)

Slide21

Facilitation: seeds and seedlings

SeedlingsDivide Mtn.—90% mortality of fir seedlings. Line Creek—63.1% mortality of spruce seedlings.No significant differences in seedling survival among microsite types at Divide Mountain or Line Creek RNA. SeedsDivide Mtn.— 20% of fir seeds germinated. Higher than expected germination occurred in rock microsites and fewer than expected in whitebark microsites (Fisher’s Exact Test, P = 0.01). On Divide, 42 out of 80 germinants survived to September. Line Creek—1.8% of spruce seeds germinated. No differences among microsites.

Slide22

Comparison of observed vs. expected cotyledon seedling survival among microsites.

--Seedlings in whitebark microsites had a 5.7 times greater than expected survival advantage over the summer. --Very low comparative risk of death (0.18 times expected). MicrositeRelative Survival AdvantageRelative Risk of DeathWhitebark5.70

0.18Spruce0.891.12Rock1.080.93

Open0.641.56

Divide Mtn. Summer survival of seedlings

Slide23

Blister rust at

treelineIntensive sampling using 15 m x 15 m plots indicates widespread blister rust infection:Divide Mountain, 23.6%Line Creek RNA, 19.2%Previous sampling at six other treeline sites in Glacier NP (15 x 15 m plots):Infection rates of 36-96%.Overall infection rate of 47%. (Smith-McKenna et al. 2011; Smith-McKenna 2013)

Slide24

Decline in treeline whitebark pine

Whitebark pine shows little or no response to global warming in upper treeline boundary Reduced ability of treeline to respond (or lag in response time) to global warming at the upper boundary

Will declines in

whitebark

pine alter

treeline

response to climate warming?

Fewer seeds dispersed to

treeline

by nutcrackers: blister rust in

subalpine

whitebark

pine

Blister rust damages and kills

whitebark

pine at

treeline

Fewer tree islands initiated by

whitebark

pine (less facilitation

)

Slide25

Agent Based Models: climate and blister rust

Smith-McKenna et al., in pressIn the ‘Climate’ scenario, both pine and spruce “agents” increased when conditions improved, and trees advanced to higher elevations into previous tundra cells. This scenario increased whitebark pine numbers by 28.8%. Both pine and spruce populations increased as tundra concurrently declined. In the ‘Climate+Disease’ scenario, mortality from blister rust reduced pine populations

despite improved site quality conditions.Both spruce populations and tundra increased. The threshold of change from dominating pine agents to spruce appeared around year 630.

Slide26

Agent Based Model preliminary results

Smith-McKenna et al., in press

Slide27

Conclusion

Our collective studies suggest:Whitebark pine tolerates harsh treeline better than associated conifers.It provides protective leeward microsites.Whitebark pine decline from blister rust will delay or impede treeline response to climate warming.Postscript What are possible reasons why whitebark pine is not a majority tree island initiator in some regions?

Cold, snowy sites support more spruce and fir than whitebark pine.Whitebark tolerates the harshest exposed sites and ridgelines.

Slide28

Postscript

Slide29

ACKNOWLEDGMENTS

Field assistance:Libby Pansing, Solé Diaz, Kodi Augare. Logistics: Glacier National Park (thanks to Tara Carolin)

Blackfeet Nation (thanks to Mark Magee)Shoshone and Custer National Forests (thanks to Ken Houston)Rocky Mountain Research Station, Ft. CollinsFinancial Support: National Science Foundation, Geography Program: L. Resler, D. Tomback, and G.

MalansonNSF BCS-0850548