TRANSFORMATION OF LARCH-DOMINATED FORESTS AND WOODLANDS INTO MIXED TAIGA

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TRANSFORMATION OF LARCH-DOMINATED FORESTS AND
WOODLANDS INTO MIXED TAIGA

• E. Levine1, H. Shugart Jr.2, J. Ranson1, N.
  Mölders3,
• J. Shuman2, R. Knox1, G. Sun4, V. Kharuk5
• 1NASAs GSFC, Biospheric Sciences Branch,
  Greenbelt, MD
• 2Dept. of Environmental Sciences, University of
  Virginia, Charlottesville, VA
• 3University of Alaska, Fairbanks, Geophysical
  Institute, Fairbanks, AK
• 4Dept. of Geography, University of Maryland,
  College Park, MD
• 5Sukachev Forest Institute, Krasnoyarsk, Russia

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Northern Boreal forest/Taiga biome
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Siberian Taiga

• One of the largest unaltered boreal forest areas
  in the world making up 19- 20 of the worlds
  forest area
• Significant carbon sink estimated to store 74 Pg
  C and 249 Pg C in the vegetation and soil,
  respectively

• Long, severe winters (up to 6 months with mean
  temperatures below freezing) and short summers
  (50 to 100 frost-free days)
• Annual temperature range -54C to 21C (-65F
  to 70F )
• with occasional extremes 73C to 32 (-100F to
  90F )
• mean annual precipitation 38 to 51 cm (15 to 20
  in)

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Major soils of the study area (US Soil Taxonomy)
(Cryosol Working Group, 2003)
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Permafrost thickness (cm) in the study area
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Siberian Larch (Larix sibirica)

• Deciduous needleleaf conifer native to Russia and
  northern China that loses it foliage each fall
• Occupies 270 million ha of boreal forest
• Siberian larch prefers light and is tolerant of
  both heat and frost, allowing it to grow on
  permafrost sites, where it is often found

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• In Northern Siberia
• Average temperatures have risen 1 to 3C (3 to
  5F) over the past 30 years, compared to the
  worldwide average increase of 0.6C (1F)
• Noticeable changes over the past few decades
  include
• increases in winter and fall precipitation
• winter warming
• higher soil temperatures
• permafrost thawing
• fires
• insect outbreaks
• ground subsidence

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Some possible effects of permafrost thawing

• warming of the soil profile
• increased depth of active layer
• increased organic decomposition
• release of CO2 and methane
• change in soil moisture storage
• increased evaporation
• increased runoff
• change in forest species
• Increased wildfires

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AREA 3
AREA 1
AREA 2
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Objectives

• Use coupled forest gap and soil process models to
  understand their process level interaction under
  different scenarios
• Identify the extent of the evergreen conifer
  invasion using a combination of well-calibrated
  satellite data and ground measurements
• Use these tools to forecast trends of forest
  species biodiversity in the region

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Questions

• Are historical areas of larch dominance in
  Siberia transforming into a zone of mixed taiga
  in areas of disturbance?
• Will the trees in this ecosystem begin to grow
  faster and gradually extend their reach farther
  north into the treeless tundra?
• Will extensive changes in the larch dominated and
  adjacent forests impact the carbon, energy, and
  water cycles of Siberia?
• Will hotter, drier conditions inhibiting growth
  and leave the forest prone to invasive species
  and wildfires?

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VALIDATION
MODEL INITIALIZATION
COMBINED MODELING

• Remote Sensing
• Predicted pixel level attributes
• height
• biomass
• species composition
• LAI
• Field Measurements
• Detailed ground knowledge

• Forest Attributes
• Remote Sensing
• Maps
• Field measurements
• (e.g. forest type and structure, disturbance
  history)
• Soil Attributes
• Maps
• Field Measurements
• (e.g. soil texture, bulk density, and horizon
  depths, moss thickness)
• Climate
• Weather Station Data
• Warming and precipitation scenarios

• Forest Model
• (FAREAST)
• Species composition
• Stand structure
• Seed sources
• Others

RESULTS

• Soil Model
• (HSTVS)
• Soil moisture flux
• Soil temperature flux
• Snow and moss insulation
• Depth of active layer thaw
• Others

• Ecological Forecasts
• Projected species composition and structure
• Areal impacts
• Model results mapped to stratified landscapes

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FAREAST A Boreal Forest Simulator
Yan, X. and Shugart, H.H. (2005) FAREAST a
forest gap model to simulate dynamics and
patterns of eastern Eurasian forests. Journal of
Biogeography, 321641-1658.

• Regeneration
• Available Light
• Soil Moisture
• Site Quality
• Depth of Thaw
• Seed Bed
• Seed Availability
• Sprouting
• Layering

• Growth
• Available Light
• Soil Moisture
• Site Quality
• Growing-Degree Days
• Depth of Thaw
• Diameter
• Age
• Height

• Mortality
• Stress
• Fire
• Insects
• Age

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Krankina O.N., et al. 2005. Effects of climate,
disturbance, and species on forest biomass across
Russia. Can. J.For.Res. 35 2281-2293
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Hydro-Thermodynamic Soil-Vegetation Simulation
(HTSVS) Mölders, N., U. Haferkorn, J. Döring, G.
Kramm, 2003 Long-term numerical investigations
on the water budget quantities predicted by the
hydro-thermodynamic soil vegetation scheme
(HTSVS) Meteorol. Atmos. Phys., 84, 115-135.

• Multi-layer soil model
• including peat, moss, and lichen
• Multi-layer snow model

• Includes simulations of
• heat conduction and water diffusion
• soil freezing and thawing and cross effects
• release and consumption of latent heat
• effects of frozen soil layers on vertical fluxes
  of heat, moisture and water vapor flux

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HSTVS Results

• Soil temperatures will be predicted more
  accurately if frozen soil physics are considered
• The soil model captures the observed seasonal
  course of soil temperature well and moisture
  acceptably
• The largest uncertainty in simulated soil
  temperature occurs around freezing
• Results are sensitive to soil properties
• Time steps larger than 10 minutes no longer
  captures the active layer effectively
• Soil properties below 1meter are important
• 20 layers and a depth of -30m provide better
  results

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Tura field station, Siberia
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