Wood quality, drought response and potential for breeding of radiata pine in marginal rainfall areas

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Wood quality, drought response and potential for
breeding of radiata pine in marginal rainfall
areas of NSW

• Julian Moreno
• PhD student University of Canterbury NZ

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Presentation outline

• Research aims with Forests NSW
• Importance of plantations in marginal rainfall
  areas
• Water use and drought response, overview
• Presentation of study and discussion of results

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Research aims with Forests NSW

• Research agreement UC (Prof John Walker)
  Forests NSW use of acoustics for resource
  characterization (Hume region radiata
  plantations)
• Development of methods for measuring green
  density and moisture condition
• Variation of green density and moisture
  condition, implications for acoustic studies
• Influence of moisture condition and temperature
  on acoustic velocity of living trees
• Wood quality and drought response in marginal
  areas

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Importance of plantations in marginal rainfall
areas

• 90 of Australia plantations are in areas with
  700 1500 mm annual rainfall (BRS 2006)
• 1992 National Forest Policy Statement (NFPS)
  restricts conversion of native forest to
  plantations
• Due to land availability and costs, new
  plantations are likely to be established in areas
  with 600-800 mm rainfall (BRS 2006)
• Australia seems to be particularly vulnerable to
  global climate change (extended droughts)

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Factors affecting tree/plantation water use
(Morris and Benyon 2005)

• Plant
• Size and growth rate
• leaf area
• sapwood area
• root biomass
• Drought/water stress response
• Stomatal response
• Xylem cavitation
• leaf senescence
• root mortality

• Climate
• Humidity
• Solar radiation
• Temperature
• Wind
• All above ? Vapour pressure deficit
  ?transpiration, stomatal response
• Water supply
• Rainfall, irrigation, groundwater
• Soil
• Texture, structure, chemistry (?storage capacity,
  hydraulic conductivity)
• Management
• site preparation
• weed control
• tree spacing
• fertilizing
• thinning pruning

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Importance of sapwood area

• Sapwood area is directly related to the stems
  water conductance ability,
• Kstemstem water conductivity
• SW sapwood area
• Kswood specific conductivity
• Slengthstem length
• SW also affects transpiration which in turn is
  related to water balance,
• T transpiration
• Vsap Sap velocity
• SW has been observed to respond more readily to
  water limitation than other physiological traits
  in stands of mature trees (Cinirella et al. 2002
  and others)

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Importance of sapwood area

• Heartwood formation in radiata pine related to
  site and physiological drought (Harris 1954)
• Bamber (1972) hypothesized that heartwood
  formation is a physiological mechanism for
  controlling sapwood area rather than a senescence
  effect

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Xylem cavitation saturation

• Xylem cavitation breakdown of conducting water
  columns due to pit aspiration
• 50 pit aspiration critical sapflow disruption
  69 saturation (Harris 1954)
• Water-conduction in radiata pine related to
  saturation percentage (Harris 1961), earlywood ?
  saturated (gt95) good conduction latewood ? sat
  65-70, high cavitation, hence poor conduction

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Breeding for drought

• Selection of physiological traits related to
  drought tolerance/resistance (Arnold et al. 2005)
• Breeders have avoided this approach because of
  the difficulty to assess such parameters
  (long-term experiments lttree water-use is
  dynamic, climate variationgt, equipment, etc.)
  (Arnold et al. 2005)
• However, it is well known that radiata pine
  (native populations) present natural adaptation
  to low rainfall and poor sites

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Presentation of study and discussion of results
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The problem (opportunity)

• 1992 National Forest Policy Statement restricts
  conversion of native forest (good sites) to
  plantations
• New land on optimal sites (high altitude-wet) has
  become very limited in the Hume region
• Increase of plantation area in ex-farm land,
  including marginal rainfall sites with high
  water deficits during the dry season
• Lack of information on the wood quality of this
  resource and the implications of marginal
  rainfall and drought

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Methods

• To date the study has included 85 mature (34-36
  years) and 130 young (10-11 years) trees
• Sampling in 2 contrasting sites (altitude
  climate) i.e. optimal vs. marginal site
  location influenced by harvesting operations at
  that time
• Mature trees included 3 different thinning
  regimes (unthinned (UT), two (T2) and three
  thinnings (T3))
• Young trees of the marginal site included two
  previous land uses (PLU) Ex-Pasture (ExP) and
  Ex-Forest (ExF)

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Location of study
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Sites description
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Methods (cont..)

• Wood quality traits 1)dynamic MOE (DMOE)
  measured by acoustic velocity (TreeTap
  DIRECTOR) and green density 2) basic density
  (BD).
• Green density and basic density measured
  destructively (discs-wedges) and
  non-destructively (12 mm cores)
• Drought response traits 1) sapwood area (SW) and
  2) sapwood saturation percentage (Sat) from
  wedges or 12 mm cores

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Determination of dry sapwood (DSW)
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Results for mature trees

• Measurements at DBH height

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The Marginal site presented way lower sapwood
area and greater variation across stands
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Note the far greater variation in saturation
during summer for the marginal site
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GD 1031 Sat 83.9
GD 1033 Sat 85.4
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Summary of effects

• Site exerted influence on both wood quality and
  drought traits, whereas thinning regime affected
  only DBH and wood quality
• The marginal site observed a reduction in
  diameter (-7 to -14), and outerwood stiffness
  (-5 to -11)
• No conclusive effect of site on basic density
• The marginal site observed greater variation and
  reduction in sapwood area (-9 to -19) across
  stands
• Far greater variation in saturation during summer
  for the marginal site

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DBH Wood quality vs. Sapwood area Marginal site
- T2 trees
Highlight high variation in all traits, extreme
SW values, trees with low values of SW good WQ,
potential for breeding
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DBH Wood quality vs. Saturation Marginal site -
T2 trees summer
Highlight high variation in all traits, very
dry-wet trees, dry trees with good WQ,
potential for breeding
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Results for young trees

• (To date)

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Summary of effects

• Large influence of site (although note
  differences between Ex-pasture Ex-forest)
• Increase in diameter (4 to 27) for the
  Marginal-ExP site however up to what age is this
  sustainable?
• The marginal sites observed a downgrade in
  stiffness (-35 to -36), and basic density
  ( -7 to -8)
• Higher variation and small reduction -yet
  statistically significant- in sapwood area for
  the marginal-ExP site
• 24 of trees of the marginal-ExP site have
  started to develop dry sapwood area
• Considerably lower saturation (84 vs. 75 - 78)
  and far greater saturation variability, for both
  marginal sites

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DBH Wood quality vs. Sapwood area Marginal-ExP
site
Highlight high variation in all traits, extreme
SW values, trees with low values of SW good WQ,
potential for breeding
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DBH Wood quality vs. Saturation Marginal-ExP
site
Highlight high variation in all traits, very
dry-wet trees, dry trees with good WQ,
potential for breeding
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Conclusions/Main findings
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Growth and wood quality

• Mature trees reduction in diameter (-7 to -14),
  outerwood stiffness (-5 to -11), no conclusive
  effect on basic density
• Young trees Increase in diameter (4 to 27) up
  to what age is this sustainable? reduction in
  stiffness (-35 to -36) reduction in basic
  density (-7 to -8)
• Additive influence of PLU on diameter for the
  Marginal-ExP, but not on stiffness and density
  (no diff between marginal sites), so are the
  latter downgrades due to the marginal environment?

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Drought response mature trees

• Trees of the marginal site have responded to this
  environment by, on one hand reducing their water
  conductance capacity as expressed by sapwood area
• On the other hand by having a much broader
  response to water stress in the dry season, as
  indicated by considerably higher saturation
  variability

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Drought response young trees

• Young trees havent reduced their sapwood area
  significantly, yet 24 of trees from the
  marginal-ExP present dry sapwood (too-big trees
  that cannot sustain large water-use anymore)
• Due to the current long drought, saturation is
  approaching critical level (69), yet there are
  very wet and very dry trees confirming the
  broad response of the species to water stress in
  the marginal sites

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Potential for breeding in the marginal sites

• Large between-tree variation in wood quality and
  drought response traits for both mature and young
  trees
• Existence of individuals with good growth,
  stiffness, and density and at the same time
  considerably smaller sapwood area and lower
  saturation
• These trees may have better water-use efficiency
  and drought tolerance
• Breeding trees with better water-use efficiency
  and drought tolerance wont affect wood quality
  (No assoc. drought traits WQ)

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Final remarks

• Variation in drought response traits between
  marginal sites for young trees suggests influence
  of factors other than climate, e.g. soil and
  previous land use (PLU)
• At what extent is the downgrade in wood quality
  of young trees related to climate only and what
  is the contribution of soil-PLU?

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Acknowledgments

• Research agreement UC (Prof John Walker)
  Forests NSW
• Tumut research centre, Ross Dickson, Carolyn
  Raymond, field staff
• Hume region, Duncan Watt, Ian Cotterill and
  planning staff, Harvesting area, Field staff
• Education NZ (NZIPR scholarship)
• CONACYT Mexico (Doctorate scholarship)