Jaclyn Ramaley / Winter Ecology / Spring 2010 Foundation Conifer of the Subalpine Forest Limber Pine / Pinus flexilis Mountain Research Station – University of Colorado, Boulder

What winter adaptations has the Limber Pine developed that contribute to its range and resilience ?

Limber Pine’s Evolution Dominate dry, exposed, rocky sites Elevation range from 1524m to 3658m Latitudinal from 33N to 51N Longevity - over 1500 years old* Co-occupy with other conifers  Ponderosa pine, Lodge pole pine, Subalpine Fur, Engelmann spruce Dispersal primarily by Clark’s Nutcracker  Trees grow in clusters or signally, considered genetic generalists * W.F. Schuster et al (1995)

Field Work Objectives & Methods Ascertain Limber Pine’s adaptations at three similar elevations on MRS Methods  Document overall site conditions  Select two slopes or aspects to measure  Select 3 healthy, dead and sapling Limper pine on each  Record tree height, diameter, windward & leeward snow at 1m and micro conditions  Measure wind speed three times at each Questions to Address with findings  What factors affect growth?  What factors affect health?  Stand dynamics – Stable or transitioning? Ascertain Limber Pine’s adaptations at three similar elevations on MRS Methods  Document overall site conditions  Select two slopes or aspects to measure  Select 3 healthy, dead and sapling Limper pine on each  Record tree height, diameter, windward & leeward snow at 1m and micro conditions  Measure wind speed three times at each Questions to Address with findings  What factors affect growth?  What factors affect health?  Stand dynamics – Stable or transitioning?

Known Adaptations of Limber Pine* Elevation - wind, atmospheric pressure, precipitation, soil characteristics Temperature – decoupled Fascicle Bundle - tight clusters, small bundles Length of shoots & twigs – returning foliage Take advantage of shoulder seasons Needle Characteristics Low Stomatal Density- # of stomata / needle volume Specific Leaf Area- high WUE *AW Schoettle et al.(2000) & M Letts et al.(2009)

Site M

Site 1 – Xeric / Open, gravel & boulder, dry soils, numerous fallen logs, juniper & bearberry patchy understory Windy on plateau, trees healthy, expansive, growing from rocks, 23 cm mean snow depth 3 m down from slope heavy growth and beetle kill As slope extends south dead trees lessen and health trees exist with SAF& LG. Saplings appear in open patches in small meadow

Site 2 – Slightly Mesic/ Flat exposed from disturbance, gravel, rocky soils, fallen logs Slightly more snow leeward of trailer Small new tree recruitment throughout Limber Pine taller windward of trailer and more robust Aspen, lodgepole and shrub encroachment

Site 3 – Northerly Ridge Top/ highest ridge point within 200 meters, bordering road to east Closely spaced trees on northeast facing slope mixed with lodgepole pine, aspen, shrubs Northeast 35% of limber dying Trees growing from boulders in deep snowpack Southwest of ridge, exposed, healthy trees

Discussion Limber pine were associated with rock or logs or both on all sites The tallest trees were on the Site 1 plateau which had the strongest winds Site 1 and Site 3 slopes had dead trees, but opposite aspects and snow pack Co-occurring conifers were the same height or taller then the limper pine What effect does understory type have?

Conclusions The Limber Pine’s ability to colonize extreme environments and withstand climate variability make it an important species  Sensitive to limiting factors of growing season  Can take advantage of the shoulder seasons and reduce growth when stresses important with global climate change  Critical to long term habitat of other species

Literature cited J.D. Coop, A. Schoettle, 20089Regenration of Rocky mountain bristlecone pine (Pinus aristata) and limber pine (Pinus flexilis) three decades after stand-replacing fires, Forest Ecology and Management 257: J.A. Donnegan, A. J. Rebertus, 1999 Rates and mechanism of subalpine forest succession along an environmental gradient, Ecological Society of American 80(4): M. G. Letts, K. N. Nkonechny, K.E. Van Gaalen, Cyndi M. Smith,2009 Physiological acclimation of Pinus flexilis to drought stress on contrasting slope aspects in Wateron Lakes National Park, Alberta, Canada, NRC Research Press 39: A. J. Rebertus, A. J. Burns, T.T.Veblen,1991 Stand dynamics of Pinus flexilis-dominated subalpine forests in the Colorado Front Range, Journal of Vegetative Science 2: A.M. Siepielski, C.W. Benkman, 2007 Convergent patterns in the selection mosaic for two North American bird-dispensed pines, Ecological Monographs 77(2): A.W. Schoettle, S.G. Rochelle, 2000 Morphological variation of Pinus flexilis (Pinaceae), a bird-dispersed pine, across a range of elevations, American Journal of Botany 87(12): W.S.F. Schuster et al., 1995 A comparison of Limber Pine (Pinus flexilis) Ages and Upper Treeline Sites East of the Continental Divide in Colorado,American Midland Naturalist 1133(1):