Managing forests that won t stand still. Richard Waring, emeritus professor College of Forestry Oregon State University

Transcription

1 Managing forests that won t stand still Richard Waring, emeritus professor College of Forestry Oregon State University

2 Outline of talk Evidence of rapid climate change in BC & USA Ecological principles that apply widely Management options for forests in transition

3 British Columbia is at the front line of climate change over last 30 yrs. Nature Climate Change 3: (2013) doi: /nclimate1836

4 Image temperature Similar trends in progressively wetter springs and drier summers in much of the western U.S.A. since 2000 Nemani & Running (1989) J. Applied Meteor. 28: Satellite-derived dryness/wetness index Drier wetter Increasing density of leaves Unpublished (2014) by Yang and Cohen O.S.U. & U.S.F.S, Corvallis, Oregon

5 Tree species with their northern range limit in British Columbia gain potential habitat at a pace of at least 100 km per decade. Hamann & Wang (2006) Ecology 87: Larch Rehfeldt and Jaquish (2010) Mitig. Adapt Strategy. Global Change 15:

6 Mountains provide refuge for species but a barrier to migration: assisted migration likely a necessity Bunnell & Kremsater (2012) Migrating Like a Herd of Cats: Climate Change and Emerging Forests in British Columbia. J. Ecosystems and Management 13:1-24.

7 Use process growth models to incorporate principles that apply to all forests tropical rainforest temperate deciduous boreal conifers temperate rainforest subtropical schlerophyll high-yield plantations

8 Process models take into account variation in climate and soils Figure courtesy of J.J. Landsberg

9 Process models must be updated by remote sensing of disturbances Masek et al. (2008) Remote Sensing of Environment 112:

10 Principle in all process models: leaves are like solar collectors poor environment, few collectors rich environment, many collectors

11 As the climate changes, so will maximum leaf area, which the models predict 1 m2/m2 2 m2/m2 10 m2/m2

12 tons biomass/ha Biomass accumulated over 5 years in eucalyptus plantation: linear with light absorbed by leaves % Light absorbed by leaves

13 Beer s Law applies fraction of light absorbed=i-exp(-k * LAI) Thinning at high LA values reduces light absorption and stand growth much less than it does at low values of leaf area

14 tree age trumps environment in determining growth rate McArdle (1961) Douglas fir yield tables. USFS. Bull. 201 Michaletz et al. (2014) DOI: doi: /nature13470

15 climate change may result in killing dominant trees with fragile plumbing Photo by Steve Wondzell Research Scientist, USFS Corvallis, OR Photo by Burke Greer Ph.D. candidate, Oreg. State Univ Soil water deficits combined with high evaporative demand can break water columns in tall trees more easily than in shorter ones Anderegg et al. (2012) Trends in Plant Science 17:

16 Relative Growth Efficiency, (wood produced/unit of leaf area) Relative Growth Efficiency, wood produced/unit of leaf area) Thinning improves tree growth per unit of leaf area Growth Efficiency, (GE) 1.0 thinned frequently 1.0 thinned once Douglas-fir 0.4 ponderosa pine Fraction of maximum leaf area Lodgepole pine Fraction of maximum leaf area Annual Yield may not be reduced much by thinning because Growth = GE/tree X Leaf Area/hectare Waring et al. (1980) Forestry 54: Larsson et al. (1983) For. Sci. 29: Coops et al. (2009) Rem. Sens. Env. 112:

17 Is this forest endangered by spruce budworm defoliation? Photo:Boyd Wickman Waring and Running (2007) Forest Ecosystems: Analysis at multiple scales. Academic Press. Photo: Boyd Wickman

18 ANS: No, only a few trees died. But why? Photo:Boyd Wickman Waring and Running (2007) Forest Ecosystems: Analysis at multiple scales. Academic Press.

19 Growth efficiency helps explain outbreaks of defoliating insects Spruce budworm outbreak in Quebec outbreak peaks Coyea & Margolis (1994) Can. J. Forest Research 24: Waring et al. (1992). Forest Science 38:

20 % max observedmortality Growth Efficiency Matters Stands with av. values >0.5 of max GE are highly resistant to bark beetle attack 40 Lodgepole > 80 years old % of maximum growth efficiency Coops et al. (2009) Remote Sensing of Env. 113: Mitchell et al.(1983) For. Sci. 29: Waring and Pitman (1983) Zeitschrift angewandte Entomologie 96:

21 Option: thin older stands to increase their resistance to bark beetles (and protect regeneration from frost) 120 year-old lodgepole pine in Oregon Deschutes National Forests, Oregon

22 Thinning must be done at least two years before bark beetles arrive Waring & Running (2007) Forest Ecosystems. Academic Press.

23 Developing genetic resistance in trees against pathogens is not a viable alterative because the pathogens evolve too rapidly semi-resistant trees die later Trees w/o resistance died first Photo by Harry Kope BC Forest Service, Smithers Yanchuk & Allard Tree improvement programmes for forest health can they keep pace with climate changes?

24 Plant densely & don t thin too early Photo by Alex Woods, B.C. Forest Service, Smithers, B.C.

25 Make disturbances more frequent in ponderosa pine forests to lower leaf area, conserve water and reduce fuel load Photos by John Bailey, OSU College of Forestry

26 Manage for mixed composition

27 Do nothing and wait for Douglas-fir to move to BC This option provides a benchmark to compare with others Tower site, Wind River, WA Photo by Youngil Kim, O.S.U. Forestry

28 Summary Use process based models to predict yields updated with remote sensing No time to breed for genetic diversity against pathogens and insects Assist migration of southern populations Plant densely and delay thinning until stand composition stabilizes Plan on shorter rotations until climate stabilizes Encourage a mixture of species Make frequent disturbances to reduce fuel levels in ponderosa pine Leave some areas untouched as benchmarks Work with UNBC to share results with the public

29 Thanks for the honor to present this Doug Little lecture Published by Island Press, 2014