Overview Successional Dynamics

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Overview Successional Dynamics
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1. How is your research specifically addressing the
   succession task (S1-S7) identified in the
   proposal?
2. New and exciting research questions that have
   come to light as a result of your work (This is
   the cool stuff you didnt know about at the time
   the proposal was written.)
3. Current research gaps and what your plans are to
   fill those gaps?
4. How are you working to tie your research to
   issues of Climate Sensitivity and
   Thresholds/Regime Shifts?

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Succession and river-floodplain interactions

• How has recent climate warming altered
  disturbance regimes and successional development
  in interior Alaska?
• Task S1 Develop predictive relationships
  among climate, glacier melt and discharge within
  and among years to assess their effects on water
  availability and nutrient supply in the Tanana
  River floodplain

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Succession and river-floodplain
interactions Hyporheic zone water chemistry
spatial patterns

• Step 1 Characterized hyporheic water
  chemistry and transformations along two
  floodplain islands
• Nitrate concentration declines as river water
  flows into the hyporheic zone indicating that
  nitrate is assimilated or denitrified along
  subsurface flowpath

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Succession and river-floodplain
interactions Hyporheic zone water chemistry
temporal patterns

• Step 1 cont Temporally, hyporheic nitrate
  concentration declines early in the active season
• However, as river flow peaks in late July,
  nitrate concentration increases, suggesting an
  influx of nitrate-rich river water into the
  hyporheic zone

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Succession and river-floodplain
interactions Hyporheic zone hydrology

• Step 2 Characterized hyporheic water hydrology
• Water table height in hyporheic zone responds
  rapidly to change in river stage

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Succession and river-floodplain
interactions Hyporheic zone hydrologic connection
with rooting zone

• Step 3 Calculate capillary rise the potential
  hydrologic connection between hyporheic flow and
  vegetation rooting zone
• Potential for hydrologic connection through
  most of the growing season

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Succession and river-floodplain
interactions Hyporheic zone nitrogen budget

• Step 4 Couple biogeochemistry with hydrology to
  calculate potential input of nitrogen from
  hyporheic zone to floodplain vegetation (early
  succession)
• Horizontal fluxes of nitrogen far exceed soil
  organic matter turnover, N fixation and N
  deposition.
• Denitrification dominant pathway for N loss
  from hyporheic water

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Succession and river-floodplain
interactions Longer-term river hydrology and
nutrient fluxes

• Step 5 Characterize the longer-term variation
  in river hydrology and the potential
  river-hyporheic zone interactions
• River discharge highly correlated with air
  temperature and glacial melt

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Succession and river-floodplain
interactions Longer-term river hydrology and
nutrient fluxes

• Next step Using long-term temperature data,
  model Tanana River discharge and the potential
  change in the coupling between hyporheic flow and
  floodplain vegetation
• River flow record fairly short-term but based on
  the record that exists the duration of saturation
  and capillary rise into rooting zone appears to
  be increasing

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Succession and river-floodplain interactions Ties
with Climate Sensitivity

• Climate sensitivity Hydrologic response of
  Tanana River provides a test of climate
  sensitivity hypothesis (H effects of climate
  change are primarily indirect, acting through
  temperature and precipitation effects on other
  variables)
• Change in river discharge is leading to an
  alteration in the timing and duration of
  river-floodplain interactions, which in turn will
  affect the delivery of water and nutrients to
  early successional vegetation

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• Task S2 - Assessing Fire Severity in Alaskan
  Black Spruce Forests
• The dNBR approach that has been proposed as a
  method for satellite mapping of fire severity was
  shown not to be a reliable approach in Alaskan
  boreal forests
• Depth of burning in Alaskan black spruce forests
  has been found to be dependent on topography,
  time of the growing season when the fire
  occurred, the size of the fire year when the fire
  occurred, and moss composition at the site

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• Studies by the NPS and CFS found strong
  correlations between dNBR and CBI, matching
  findings in other U.S. biomes
• Using fire events from 2004, UMD/MSU/Mich Tech,
  UAF, and FWS scientists found weak correlations
  between dNBR and CBI

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Topography and climatic factors combine to
control depth of burning in black spruce forests.
Climate Controls In late season fires, thawing
of the ground layer leads to drier organic layers
through improved drainage Droughts lead to drier
organic layers and deeper burning in larger fire
years in early season fires.
Topographic Controls Topography controls soil
drainage and microclimate (which controls
permafrost) both these factors influence organic
layer moisture and level of burning
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Species controls on patterns of fuel consumption

• Ecohydrology traits of several dominant Sphagnum
  species lead to high moisture retention

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Sphagnum sheep
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Soil OM reduction ()
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• Microsites dominated by hummock Sphagnum have
  lower consumption rates than adjacent microsites

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Feather mosses
Sphagnum
Shetler et al. in review
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Research Gaps and Questions?

• In black spruce forests and other ecosystems with
  deep organic layers, how do seasonal variations
  in climate control depth of burning?
• How vulnerable are wetlands to burning?
• How does depth of burning relate to the
  vulnerability of an ecosystem, e.g., how do we
  interpret depth of burning data with respect to
  thresholds?
• How does one measure fire severity within and
  across ecosystems?
• What factors other than fire severity contribute
  to vulnerability?

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Plans to Address Research Gaps

1. We have installed soil temperature and moisture
   probes in 4 different black spruce (2 in BC, 1 in
   PC, and 1 at Washington Creek) stands to collect
   data to monitor seasonal variations in duff
   moisture. We plan to correlation duff moisture
   with Fire Weather Indices derived from weather
   data
2. We have submitted a proposal to collect depth of
   burning data in wetland sites

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Addressing Research Questions How do we relate
depth of the remaining organic layer or depth of
burning to ecosystem vulnerability?
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Task S3. Analyze the relationships among climate,
disturbance regime, ecosystem structure
(vegetation composition and organic layer depth)
and permafrost distribution - V. Romanovsky

• Permafrost is product of cold climate and hence
  is sensitive to changes in climate
• However, it is also very sensitive to local
  surface and soil conditions and because of that
• Permafrost is very sensitive to changes in the
  surface vegetation
• Permafrost stability in the warming climate
  especially depends on organic layer depth
• Disturbance regime (both natural and human-made
  disturbances) has direct effect on permafrost
  stability
• 3. Permafrost temperature is much more sensitive
  to these changes and react quickly, permafrost
  thickness and distribution are much more inertial
  and change slowly

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Low heat flux at the permafrost surface
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Task S4. Analyze the relationship between
disturbance properties and plant successional
pattern as a basis for rule-based models of
succession

• Contributing PIs Jill Johnstone, Teresa
  Hollingsworth, Terry Chapin, Scott Rupp, Dave
  Verbyla
• Students Emily Bernhardt, Leslie Boby, Katie
  Villano
• Techs Julie Benioff, Emily Tissier, Mark Olsen

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Fire effects on succession

• Impacts of fire severity on succession in black
  spruce
• 2004 wildfires landscape study (JFSP)
• Important steps
• Build off solid base of previous research
• Obtain large-scale dataset coverage
• Assess initial hypotheses with new data
• Extract patterns into qualitative rules
• Develop probabilistic models to identify
  thresholds

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Overview

• Data example Building understanding of fire
  effects on tree recruitment (3 slides)
• Extracting patterns to develop qualitative rules
  (3 slides)
• Some surprises and gaps
• Next steps

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Experimental seedling recruitment
Standardized germination rate
Residual organic layer depth (cm)
Data are from 5 sites in Alaska/Yukon, and have
been standardized by the site mean so that zero
reflects average recruitment.
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Natural tree recruitment (8 years after Delta 94
burn)

• Spruce seedling density
• Weak negative response to increased surface fire
  severity
• Contrary to experiments
• Possibly reflecting poor competitive ability with
  aspen

• Aspen canopy biomass
• Strong positive response to increased fire
  severity
• Consistent with experiments
• Indicates positive effect on both recruitment
  (density) and growth

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JFSP research on 2004 burns Experimental seeding
trials (n38)
Conifer seedling density
Deciduous seedling density
Difference in the slope of conifer and deciduous
responses is key
cover of organic soil
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What the data are saying

• Spruce self-replacement maintained by
• Increased ability to germinate on organic soils
• Large numbers of on-site seed
• Can shift to deciduous-dominated when
• Deep burning exposes mineral soil increased
  recruitment of deciduous trees
• Sites are dry or permafrost thaws supports
  warmer soils and increased growth of deciduous
  trees

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Successional trajectories key

• Qualitative rules to predict trajectories of
  post-fire recovery
• Alaskan black spruce forest
• Integrates moisture and severity effects
• Rapid assessment of post-fire stands
• Identify conditions leading to change

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Moist site with intact organic layer

• Rapid assessment
• thick organics but good moisture
• trees standing with cones intact
• Predicted recruitment
• very little deciduous
• low to high black spruce (depending on quality of
  organics)
• Trajectory open to closed black spruce

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Moist site with low residual organics

• Rapid assessment
• shallow organics with good moisture
• trees fallen (reduced seed dispersal)
• deciduous seed source within 1-2 km
• Predicted recruitment
• high deciduous
• low to moderate black spruce
• Trajectory mixed deciduous black spruce

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Surprises Data Gaps

• Inherent stochasticity of recruitment?
• Lots of data, but still lots of uncertainty
• Eg. Little response to seed availability
• Zero recruitment observations gt deforestation or
  just delayed?
• Remote sensing detection of high surface
  severity?
• Through the looking glass Assessing future
  trajectories

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Next steps

• Collect more data
• integrate recruitment, survival, and growth
• Identify quantitative thresholds
• probabilistic or decision-tree models
• Assess community level responses
• entrained by tree dominance?
• Use simulation experiments
• impacts on forest cover and future fire behaviour
  (ALFRESCO)

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• Task S5. Document the effects of key plant
  functional types on ecosystem processes.
• Improve our predictive understanding of the
  response of key plant functional types to
  interactions of legacies and disturbance
• Improve our understanding on how key plant
  functional types affect ecosystem function
• Alder
• Mosses
• Invasive plants
• Dominant tree species

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1. Alnus tenuifolia and Alnus viridis Patterns
of and controls over N inputs by green alder to
secondary successional upland forests (Mitchell
and Ruess a,b, submitted). Landscape-scale
patterns of thin-leaf alder population and
community dynamics along the Tanana River
(Nossov) The alder canker outbreak physiology,
population, and ecosystem-level responses
(McFarland, Nossov, Rohrs-Richie,
Ruess) Ecosystem consequences of mutualist
partner choice in thin-leaf alder (Ruess,
Anderson, Kielland, Taylor)
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Ecosystem consequences of mutualist partner
choice in thin-leaf alder
Cost of N2 fixation
9.9 0.7 µmol C respired / µmol N fixed (n150)
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• Alder Current research gaps that were working
  on
• Interactions between N and P cycling
• Effects of N-fixation inputs on C storage
• Alder stem canker What triggered the outbreak?
  Has this happened before? What are the long-term
  consequences of this disease?
• Moose-alder interactions the consequences of
  alder legacies

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2. Sphagnum and feather mosses The relationship
between moss species composition and ecosystem
characteristics in black spruce forests
(Hollingsworth, Schuur, Chapin (in
revision). Role of mosses in peatland ecosystem
dynamics (Turetsky) Small scale moss transplant
studies, and moss N retention studies
(Mack) Long-term trends in moss abundance and
composition (Hollingsworth, Lloyd, Mack,
Turetsky) Influence of mosses on vascular plant
invasions (Villano)
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The relationship between soil carbon accumulation
and Sphagnum diversity

• Acidic black spruce communities (ABSC) have
  higher abundance and richness of Sphagnum
• NBSC, however, have an overall higher moss
  richness

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Role of mosses in ecosystem N retention
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High bryophyte abundances in high severity and
unburned sites reduced the final biomass of
invasive species H. aurantiacum and B. inermis.
H. aurantiacum in soils from a high severity, wet
burn site with abundant bryophytes.
H. aurantiacum in soils from a low severity, dry
burn site with few bryophytes.
We found invasive asters (Crepis tectorum) in the
field more often in sites with less bryophyte
cover.
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• Mosses current research gaps (some we are
  kinda, sorta, maybe working on)
• What is the mechanism behind the correlation
  between moss diversity and ecosystem
  characteristics?
• What is the function of Sphagnum sheep
  post-fire?
• Rich fens versus poor fens versus bogs
• Overall, very few moss studies have been done,
  even though we know mosses are so important to
  the functioning of the boreal forest.

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3. Invasive Plants

1. Surveys of burned areas for invasives along the
   Parks, Dalton, Steese, and Taylor Highways
   (Villano and Mulder, NPS)
2. Susceptibility of burned sites to invasion how
   abiotic factors (burn severity, moisture) and
   competition by ground cover species affect
   germination, survival and growth of three
   high-risk non-native species (Villano, Mulder, T.
   Hollingsworth)
3. Competition between Melilotus alba and native
   plants, particularly legumes field removal
   experiments, shading experiment, competition
   experiment with two native legumes (Spellman,
   Wurtz)

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Regional Differences in Invasibility (beyond
propagule pressure)

• Invasives grown in Dalton and Taylor Highway
  soils had 75 greater biomass and 77 more
  tillers than in the Steese soils.
•  Few differences in organic or mineral soil
  variables
• Compared to cores from the Dalton or Taylor
  Highway sites, cores from Steese Highway sites
  had significantly greater non-vascular biomass
  and cover, vascular cover and native plant
  richness.

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Research Gaps Invasive Plants

• 1) How do biotic factors, including herbivores
  and pathogens, accelerate or retard the advance
  of invasives in burned habitat? (Mulder lab,
  proposal in progress)
• 2) Which environmental factors related to climate
  change directly affect fitness of non-natives?
• 3) Ability of invasives to invade intact boreal
  forest

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S5 Relationships with Climate Sensitivity Landsc
ape variation in growth sensitivity of alder to
interannual variability and long-term trends in
ppt (Nossov) Drought-related sensitivity of
alder to canker (Rohrs-Richie, Nossov,
Ruess) Changes in moss abundance over the last
25 years at the LTER vegetation sites
(Hollingsworth, Lloyd) How fire severity effects
on the abundance of deciduous broadleaved trees
influences net climate forcing over secondary
succession influence of alternative successional
trajectories in upland black spruce forest
(Mack)
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S5 Relationships with thresholds and regime
shifts Consequences for disease-related changes
in alder abundance Role of Sphagnum (or the loss
of Sphagnum) in predicting regime shifts
post-fire. Climate change and potential
thresholds for invasives direct (climate
thresholds for growth) and indirect (climate
effects on disturbances) on invasion success
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• Task S6. Determine the long-term effects of
  snowshoe hares and moose on ecosystem processes
  in floodplain succession (Kielland).
• Current studies
  Location Focus
• Moose/hare exclosures (est. 1989) FP1,2
  Sp, Soil C, Pop dynamics
  
• Moose/hare exclosures (est. 2005) FP1,3,5
  Sp, C,N
• Spruce-moose exclosures (est. 2002) FP1
  Sp, Spruce growth/physiol
• Yukon moose-succession
  YFlats Sp, theory/model
• Moose - Fire
  RCB, DJ Forage prod, comp, CP

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Browsed Control
1989 1995 2001
2007
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y -0.071x 0.139 R2 0.5726 P0.007
y -0.11x2 - 0.04x 1.46 R2 0.75 P0.002
Exclosure -2.62x 28.82 R2 0.72 P0.033
y -0.15x 1.60 R2 0.18 P0.047
Control -1.03x 28.47 R2 0.44 P 0.015
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Landscape perspectives and modeling
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Yukon River
Tanana River
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Moose density (km-2)
Moose Wolf ratio Willow Alder ratio
West Tanana Flats 0.5
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1.9 East Tanana Flats 2.5
65 0.8
Butler and Kielland 2008
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• Current studies
  Relationship to other LTER research
• Moose/hare exclosures (old) Alder
  project, Successional dynamics, nutr. cycling
• Moose/hare exclosures (new) Veg.
  dynamics, nutr. cycling, hydrology
• Spruce-moose exclosures
  Succ.dyn,/theory, plant physiol, biogeochemistry
• Yukon moose-succession Succ. dyn.
  model, wildlife
• Moose - Fire
  Post-fire succession, productivity, wildlife,
  JFS

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Successional Processes - Taylor Lab Hypothesis
Climate influences the rate and trajectory of
succession by altering disturbance regime and the
abundance of key species. 2. How do legacies
and disturbances interact to determine changes in
abundances of key plant, animal and microbial
taxa through succession and what are the
consequences for ecosystem processes? Task S7.
Establish baseline characterization of soil
fungal community composition among successional
stages, soil horizons, and seasons in floodplain
and upland ecosystems.
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Successional Processes - Taylor Lab What we are
doing Summer sampling of fungal community
structure sampled Core BNZ Upland sites UP1-3
in 2004, 2005 sampled 12 TKN black spruce
sites in 2004, 2005 sampled Floodplain FP5C
and BP3 have generated 100,000 soil clone
sequences Seasonal study set up a snow
manipulation plot on campus, white spruce
sampled in summer, fall, winter, spring
generated 9000 soil clone sequences
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Successional Processes - Taylor Lab Results 1
strong structure across soil horizons
FP5C Black Spruce Site
Green litter Black humic
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Successional Processes - Taylor Lab Results 2
Plant-associated fungi dominate over saprotrophic
fungi
FP5C Black Spruce Site
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TKN Black Spruce Sites
Successional Processes - Taylor Lab Results 3
Similar diversity in wet vs dry years higher
diversity in nonacdidic sites
Dominants only - 3900 species found!!!
Acidic
Non-acidic
Green drought Red normal
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Successional Processes - Taylor Lab Fungal
Community Structure Across Seasons and Soil
Horizon
Ian Herriott, MS Thesis
mineral
organic
White spruce stand, ski trails
humic
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Successional Processes - Taylor Lab New,
exciting directions collaboration with
Lawrence Berkeley Labs to build a fungal
phylochip possibility of assaying bacterial
community structure using our existing soil DNA
samples and LBLs bacterial phylochip
expanding our RNA-based analyses of active
communities across seasons
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Successional Processes - Taylor Lab Research
gaps and plans to fill them Have not fully
characterized fungal community structure across
floodplain successional stages phylochip???
Have only characterized active (RNA) versus
resident (DNA) communities in a single soil core
new IPY Cold Fungi grant Have not looked
at fungal succession post-fire proposal with
JFSP team
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Successional Processes - Taylor Lab Ties to
climate sensitivity, regime shifts
Comparison of 2004 (dry) with 2005 (wet) fungal
communities IPY Cold Fungi grant for Ians
snow manipulation/seasonal RNA vs DNA study
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Task S1. Relationships among climate, glacier
melt, and discharge effects on water
availability and nutrient supply in the Tanana
River floodplain
Task S3. Relationships among climate, disturbance
regime, ecosystem structure (vegetation
composition and organic layer depth) and
permafrost distribution
Task S2. Relationships between climate and fire
regimes
Task S4. Relationships between disturbance
properties and plant successional pattern as a
basis for rule-based models of succession
Task S5. Effects of key plant functional types on
ecosystem processes
Task S6. Long-term effects of snowshoe hares and
moose on ecosystem processes in floodplain
succession
Task S7. Baseline characterization of soil fungal
community composition among successional stages,
soil horizons, and seasons in floodplain and
upland ecosystems
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