Genetic variation in drought hardiness in southwest Oregon Douglasfir

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Genetic variation in drought hardiness in
southwest Oregon Douglas-fir
Glenn Howe, Department of Forest Science
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Genetic variation in drought hardiness in
southwest Oregon Douglas-fir
Question

• In southwest Oregon, do populations of
  Douglas-fir from north- and south-facing slopes
  differ in drought hardiness?

Justification

• For reforestation (e.g., after fires), it's
  important to know whether north- and south-facing
  slopes should be regenerated with the same or
  different seed sources

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Genetic variation in drought hardiness in
southwest Oregon Douglas-fir
Background
Southwest Oregon - a region of Oregon that is
characterized by hot, dry summers Seed source -
the locality or parent(s) from which a seedlot
was collected Drought hardiness - the ability of
plants to tolerate drought Common-garden
experiment - an experiment in which different
seedlots are grown at the same location under
uniform environmental conditions to assess their
genetic differences Natural selection - the
differential, non-random survival of individuals
that differ in hereditary characteristics
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Genetic variation in drought hardiness in
southwest Oregon Douglas-fir
Question

• In southwest Oregon, do populations of
  Douglas-fir from north- and south-facing slopes
  differ in drought hardiness?

Justification

• For reforestation (e.g., after fires), it's
  important to know whether north- and south-facing
  slopes should be regenerated with the same or
  different seed sources

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Genetic variation in drought hardiness in
southwest Oregon Douglas-fir
Axioms

• In southwest Oregon, drought stress is greater on
  south-facing slopes than on north-facing slopes
• Drought stress is an important cause of mortality
  of Douglas-fir seedlings
• Genetic variation in drought hardiness exists
  among Douglas-fir trees and populations

Assumptions
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Genetic variation in drought hardiness in
southwest Oregon Douglas-fir
Hypothesis/Postulate

• In southwest Oregon, trees collected from
  south-facing slopes are genetically more
  resistant to drought than are trees from
  north-facing slopes

Scope of inference

• Douglas-fir populations from drought-prone areas
  in southwest Oregon

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Data statement I will
Collect seed from many trees on each of three
paired north- and south-facing slopes (field
design randomized block design treatment
aspect) Grow the seedlings in raised nursery
beds in Corvallis Oregon (nursery design
randomized block design treatments aspect,
drought) Withhold water from drought treatment
after the trees become established Measure
drought hardiness (growth physiology
mortality) Test for statistically significant
and biologically relevant differences in measures
of drought hardiness between the populations from
the different aspects
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Field and Nursery Design
1. Field design
2. Nursery expt
South
North
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Drought Hardiness Measurements
1.
Impose drought
2. Measure Growth Photosynthesis Cavitation
Mortality
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Drought Hardiness Analyses
3. Statistical tests Relevance
Expected Results
If my hypothesis is correct, I expect the
seedlings from south-facing slopes to have lower
xylem cavitation, greater growth, greater
photosynthesis, and higher survival in the
drought treatment, but not in the control