Understanding the Biocomplexity of Small Arctic Patterned-Ground Features
1. Lesson 3:
Biocomplexity of small patterned-ground features
D.A. (Skip) Walker
Alaska Geobotany Center,
Institute of Arctic Biology, UAF
2. Overview of talk
Introduction:
• What is biocomplexity?
• What are patterned-ground features?
• Why is this an important topic?
• Conceptual models of patterned ground formation.
Overview of results from project components:
• Climate and permafrost
• Soils and biogeochemistry
• Vegetation
• Modeling
• Education
3.
4. Goal of the Biocomplexity of Patterned-Ground
Project
To better
understand the
complex linkages
between frost
heave, frost
cracking,
biogeochemical
cycles, vegetation,
disturbance, and
climate across the
full Arctic summer
temperature
gradient in order
to better predict
Arctic ecosystem
responses to
changing climate.
Biocomplexity Grid at Green Cabin, Banks Island, Canada,
2003
6. BECAUSE:
• The processes involved in
the formation of patterned-
ground landscapes are not
well understood.
• The importance of patterned
ground with respect to
biogeochemical cycling,
carbon sequestration and
other ecosystem processes
is poorly known.
• They are an ideal natural
system to to help predict the
consequences of climate
change of disturbed and
undisturbed tundra across
the full Arctic climate
gradient.
7. Frost-heave Complexity Questions
Self organization
– How do frost-heave features self-organize themselves?
– How is vegetation involved in this process?
Complex adaptive systems
– How do frost-heave and associated ecosystems change
along the arctic climate gradient?
– How does the vegetation affect the microclimate, ground
ice, disturbance, and soils of frost-heave features along
the Arctic climate gradient?
Scaling issues
– What are the emergent properties of frost-heave
systems at different scales?
– How do frost-heave features affect trace gas fluxes,
hydrological systems, and patterns of wildlife at large
spatial scales?
8. Variety of frost-boil and earth
hummock forms along the
Arctic climate gradient
• Subzone A and B: Mainly small
polygons with vegetation concentrated
in the cracks.
• Subzone C: Larger polygons, and frost-
boils ( nonsorted circles) with
vegetation in the cracks and margins of
circles and mostly barren frost boils.
• Subzone D: Partially vegetated circles
with well-vegetated inter-circle areas
with thick moss mats.
• Subzone E: Mainly small circles and
earth hummocks thickly covered in
vegetation.
9. Some forms caused
by differential frost
heave
• Frost-heave non-sorted circles
• Earth hummocks
Non-sorted circles, Howe Island, AK, Subzone E.
Earth hummock, Inuvik, NWT, Canada,, Northern Boreal Forest.
Non-sorted circles, Franklin Bluffs, AK, Subzone D.
Photos: D.A. Walker
10. Earth hummocks caused by differential frost heave
Earth hummocks, Subzone B, Mould Bay Incipient earth hummocks in large non-
sorted seasonal frost-crack polygons,
Subzone C, Green Cabin
Earth hummock, Subzone E, Happy Valley Earth hummocks, northern boreal forest,
Inuvik, NWT
11. Complexities caused by
slope, soil moisture and
rocky soils
• Stripes on slopes
• Very large non-sorted circles in wet
sites.
• Sorted circles in rocky soils.
Non-sorted stripes, Subzone C, Green Cabin.
Large non-sorted circles in wet soils, Green Cabin. Sorted Circles at Mould Bay, Canada, Elevation
Belt A. Photos: D.A. Walker
12. Contraction Cracking
• Small non-
sorted
polygons
(Washburn
1980).
• Occur on most
sandy to clayey
soils in the
High Arctic
(Subzones A,
B, C).
Mould Bay, Prince Patrick Island, •
Contraction cracks in a drained lake basin, Seasonal frost
Elevation, Belt A. Prudhoe Bay, Alaska, Subzone D. cracking
(Washburn
1980).
• Can be
confused with
desiccation
cracking.
Green Cabin, Banks Island, Howe Island, northern Alaska,
Bioclimate Subzone C. southern Bioclimate Subzone C.
Photos: D.A. Walker
13. Modification of small polygons to form turf
hummocks
• Erosion and eolian
deposition modify
the basic forms
resulting in turf
hummocks (Broll
and Tarnocai 2003).
Turf hummocks on slopes with Dryas integrifolia and Cassiope
tetragona,
14. In the High Arctic, small contraction-crack polygons are the
dominant patterned-ground features.
• Small non-
sorted
polygons
(Washburn
1980).
• Occur on
soils of all
textures in
the High
Arctic.
Mould Bay, Prince Patrick I.
• May be
caused by
either
desiccation
cracking or
seasonal
frost
cracking
(Washburn
1980).
Isachsen, Ellef Ringnes I. Howe Island, northern Alaska
Photos: D.A. Walker
15. Desiccation cracking vs. seasonal frost cracking
Desiccation
cracking:
• Washburn
(1980) and
Tricart (1967)
attributed
most fine-
scale (<1-m
diameter
polygons) to
desiccation
cracking.
Seasonal frost
Desiccation cracks. Desiccation cracks. cracking:
Mould Bay. Dinosaur Provincial Park, Alberta.
• Ubiquitous
on most High
Arctic
surfaces.
• All soil
textures.
• Deeper
cracking.
• Experiments
and models
are needed
to determine
conditions
Green Cabin, small non-sorted polygons Green Cabin, polygon removed from soil.
16. Frost cracking occurs at many scales
Permafrost crack nonsorted polygons, Kupar;uk Small seasonal frost-crack non-sorted polygons,
R., Alaska Green Cabin.
Frost cracking within small polygons, Mould Bay. Frost cracking within Dryas hummock, Green Cabin.
17. Role of soil texture
Rocky soils: sorted circles and polygons, Sandy soils: no circles nor hummocks
Mould Bay, Prince Patrick I. Atkasuk, AK
Silty soils: sorted circles without earth hummocks Clayey soils: earth hummocks,
Prudhoe Bay, AK Inuvik, NWT
18. Variety of forms on different substrates
Stoney substrates:
Mould Bay, Prince Patrick I.
19. Variety of forms on different substrates
Saline sandy loam substrate:
Howe Island, Alaska
20. Variety of forms on different substrates
Mesic loamy substrates:
Southern Yamal Peninsula
(above), Kurishka, Kolyma
R. (right)
21. In general:
• Circular forms are caused by differential heave resulting in
circles and earth hummocks.
• Polygonal forms are caused by cracking (thermal or
desiccation):
– Large polygons (thermal contraction cracking penetrates deep
into the permafrost)
– Small non-sorted polygons (contraction cracking confined to
zone of seasonal thaw)
• Both differential heave and cracking can occur at a variety
of scales forming complex landscape patterns.
• The forms can be modified by soil texture and a wide
variety of processes including sorting (sorted forms),
erosion and eolian deposition (turf hummocks, high-
centered polygons), down-slope soil movement (stripes
and lobes).
22. Project initially focused on “frost boils”
• Caused principally by
differential frost heave
(Peterson and Krantz 2003).
• Also called:
• Non-sorted circles (Washburn 1980)
• ‘Frost medalllions’ (Russian term),
• ‘Mud boil’ (Zoltai and Tarnocai 1981)
• ‘Frost boi’ (van Everdingen 1998)
• ‘Frost scar’ (Everett 1966)
• ‘Spotted tundra’ (pyatnistye tundry,
(Dostoyalov and Kudravstev 1967).
Subzone C, Howe Island, AK.
Photo; D.A. Walker
23. What are non-sorted circles?
Sorted circles = Frost boil: “a patterned ground form that is
equidimensional in several directions with a dominantly
circular outline which lacks a border of stones…”
van Everdingen 1998
• Frost “boil” is a misnomer because no “boiling” is
involved.
• Closest term in Russian is Piyatnoe medalion - “frost
medallion”
• Moroznoe kepenie - frost churning due to needle-ice
formation.
• Pyatneestaya tundra: “spotted tundra” in Russian
Nonsorted circles
Figures from Washburn 1980
24. The non-sorted circle system
Sparsely vegetated circle
Vegetated inter-circle
area
Courtesy of C. Tarnocai
25. Central Questions
• How do
biological and
physical
processes
interact to form
small patterned
ground
ecosystems?
• How do these
systems
change across
the Arctic
climate
gradient?
Howe Island, AK.
Photo; D.A. Walker
26. Conceptual model of the non-sorted circle system
Non-sorted Circle Inter-circle area
Vegetation
Vegetation
Ice Ice
Soil Lenses Soil
Lenses
The white arrows indicate interactions and feedbacks between
elements (frost boils and inter frost boils), and black arrows
between components of each element (ice lenses, soils, and
vegetation).
27. Examination of frost heave features across the Arctic
bioclimate gradient
Sub- Mean Dominant plant
zone July growth forms Arctic bioclimate subzones
tempera-
ture (˚C)
A 2-3 Cushion forbs,
mosses, lichens
B 3-5 Prostrate dwarf
shrubs
C 5-7 Hemi-prostrate
dwarf shrub,
sedges
D 7-9 Erect dwarf
shrubs, sedges
mosses A
B
E 9-12 Low shrubs,
C
tussock sedges,
D
mosses
E
From the Circumpolar Arctic Vegetation Map, 2003.
28. Dominant drivers of patterned-ground formation across
the Arctic bioclimate gradient
Non-sorted circles Inter-circle areas
Cold climate (subzone A)
Vegetation Vegetation Dominantly physical
processes on both circles and
inter-circle areas
Ice Lenses Soil Ice Lenses Soil
Moderate climate (subzone C)
Vegetation Vegetation Dominantly physical
processes on circles and
biological processes in inter-
circle areas
Ice Lenses Soil Ice Lenses Soil
Warm climate (subzone E)
Vegetation Vegetation Dominantly biological
processes on both circles
and inter-circle areas
Ice Lenses Soil Ice Lenses Soil
33. Project components
• Climate and permafrost: Vladimir Romanovsky, Ronnie Daanen,
Yuri Shur
• Soils and biogeochemistry: Chien-Lu Ping, Gary Michaelson,
Howie Epstein, Alexia Kelley
• Vegetation: Skip Walker, Anja Kade, Patrick Kuss, Martha
Raynolds, Corinne Vonlanthen
• Modeling: Ronnie Daanen, Howie Epstein, Bill Krantz, Dmitri
Nikolsky , Rorik Peterson, Vladimir Romanovsky
• Education: Bill Gould, Grizelle Gonzalez
• Coordination and management: Skip Walker
34. Climate and
permafrost
component
Vlad Romanovsky
35. The ice-lens part of the
nonsorted-circle system
Ice lenses
• Ice lenses drive frost heave.
• Numerous closely spaced lenses form as
the soil freezes downward from the
surface.
• The increased volume of the water
causes heave.
• Heave also is caused by formation of ice
at the bottom of the active layer as the
soil freezes upward.
Frozen soil core from a frost boil
Photo Julia Boike
36. These processes are described in three models of
differential frost heave (Peterson and Krantz 2003,
Daanen et al. 2008, Nickolsky et al. 2008).
Briefly:
• Heat preferentially escapes from the surface at high points of
20 cm organic small irregularities in the surface.
horizon
• These high points self-organize into patterns controlled by
mechanical properties of the soil (e.g., texture) and active
layer thickness.
Nonsorted
• These high points are sites of increased heat and water flux,
Inter-
circle
circle ice-lens development, and more heave. Water is pulled to the
site of freezing by cryostatic suction.
Lenticular voids in soil in summer
created by ice lenses.
Schematic of soil undergoing top-down freezing. Ice
lenses exist in the frozen region and permafrost
underlies the active layer.
37. Frost heave measurements
• Differential heave
is the greatest in
subzone D,
where centers
are unvegetated
but areas
Soil Heave between features
30.0
are well-
Centers of PG features
22.5 Between PG features
vegetated.
Heave (cm)
15.0
• Heave greatest in
7.5
northern Alaska
on silty soils
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41. Complete
characterization of
soils
• Large soil pits across full
patterned ground cycle.
• Lots of student help.
42. Current Buried carbon in the
Active intermediate layer of
Layer
permafrost table
Intermediate Layer of
Upper Permafrost
Courtesy of Gary Michaelson
43. Sequestered carbon beneath frost boils
Carbon-rich horizon at base of non-
sorted circle
Movement of
carbon from
margin of circle to kg OC m-2
the base of the Active layer – 37
Permafrost – 19
circle via gravity Total 56
44. Carbon is concentrated in the cracks between
small polygons.
Nonsorted circles, Ostrov Belyy, Russia. After removal of top 10 cm of soil.
Circles are situated in the centers of 60-90-cm diameter nonsorted
polygons with cracks.
45. Movement of organic material along thermal
cracks to the base of the active layer.
Photos: Left and center: Laborovaya, Russia; right: Mould Bay, Canada
46. Large amounts of carbon are sequestered at
the top of the permafrost table in the
intermediate layer.
Major questions:
Courtesy of Misha Kenevskiy & Yuri Shur
How old is the carbon?
How stable is the carbon?
Is it susceptible to
decomposition if the active
layer becomes deeper?
47. Structure of active layer and top permafrost layers
beneath a nonsorted circle.
1 – Active layer (zone of annually thawed soil).
2 – Transient layer (frozen in some summers and
thawed in).
3 – Intermediate layer).
4 – Original permafrost.
Arrows denote hyphothsized movement of organic
56. Spatial
variation in
soil properties
across a non-
Available Nitrogen (ug cm-3)
sorted circle
6
5
3
2 Michaelson, G.J., Ping, C.L.,
0
interboil rim >3cm <3cm Bare
Epstein, H., et al. 2008.
Soils and frost boil
ecosystems across the
Water Content (cm3 cm-3)
1.0 North American Arctic
Transect. Journal of
0.5
Geophysical Research -
0 Biogeosciences. 113:1-11.
interboil rim >3cm <3cm Bare
Inter Rim >3cm <3cm Bare Ping, C.L., Michaelson, G.J.,
Boil Veg. Veg. Soil
Kimble, J.M., et al. 2008.
Cryogenesis and soil
formation along a
bioclimate gradient in
58. The added roles of
vegetation
Plant cover:
• Insulates the surface decreasing the
heat flux and summer soil
temperatures.
• stabilizes cryoturbation and limits
needle-ice formation.
• Promotes nitrogen and carbon inputs
to the soil.
Bill Steere collecting Bryum wrightii on a frost
N, Matveyeva - Map and drawing of frost boil at Prudhoe Bay, July, 1971.
boil vegeation on the Taimyr Peninsula,
Russia.
59. Approach: Measurements along the NAAT
Measurements
• 21 Grids and maps
• Active layer
• Vegetation
• Snow
• Climate /permafrost
• Met station
• Soil temperatures
• Frost heave
• Soils
• Characterization
• Nitrogen
mineralization
• Decomposition
• Remote sensing
• NDVI
• Biomass
10 x 10 m grid at Isachsen
60. North American Arctic Transect
Arctic Bioclimate
Subzones
Sub- MJT SWI
zone (˚C) (˚C mo)
A <3 <6
B 3-5 6-9
C 5-7 9-12
D 7-9 12-20
Canada
E 9-12 20-35
Dalton Highway (7 locations)
Forest >12 >35
61. Subzone A: Subzone D:
Satellite Bay, Canada - 1
Biocomplexity grids Deadhorse, Alaska - 1
Isachsen, Canada - 3 planned Franklin Bluffs, Alaska - 3
Subzone B: Sagwon MNT, Alaska- 2
Mould Bay, Canada - 2 Ambarchik, Russian - 1
Subzone C: Subzone E:
Howe Island, Alaska - 1 Sagwon MAT, Alaska - 1
West Dock, Alaska - 1 Happy Valley, Alaska - 3
Green Cabin, Canada - 3 Kurishka, Russia - 1
TOTAL 20 + (3 planned) = 23
Happy Valley Grid
62. Vegetation mapping and analysis of
Martha Raynolds
of active-layer/heave/vegetation
relationships
Anja Kade
63. Small landscape maps along climate gradient:
10 x 10 grids
Maps of 10 x 10 m study areas (Raynolds et al. 2008, JGR).
Raynolds, M.K., Walker, D.A., Munger, C.A., et al. 2008. A map analysis of patterned-
ground along a North American Arctic Transect. Journal of Geophysical Research -
Biogeosciences. 113:1-18
64. Trends in patterned-ground morphology and
vegetation on zonal sites across the Arctic
bioclimate gradient
68. Classification of patterned-ground vegetation along
Plant communities
the NAAT Soil and site data
• Used the Braun-Blanquet
appraoch.
• Low Arctic: Kade, A., Walker,
D.A., and Raynolds, M.K., 2005,
Plant communities and soils in
cryoturbated tundra along a
bioclimate gradient in the Low
Arctic, Alaska: Phytocoenologia, v.
35, p. 761-820.
• High Arctic: Vonlanthen, C.M.,
Walker, D.A., Raynolds, M.K., Kade,
A., Kuss, H.P., Daniëls, F.J.A., and
Matveyeva, N.V., 2008, Patterned-
ground plant communities along a
bioclimate gradient in the High
Arctic, Canada: Phytocoenologia, v.
38, p. 23-63.
69. Plant community table (cover)
Plant species and cover
information for each plant
community
Classification according to
Braun-Blanquet approach
Kade et al. 2005, Plant communities and soils in
cryoturbated tundra along a bioclimate gradient in the Low
Arctic, Alaska. Phytocoenologia, 35: 761-820.
70. Frost-boil plant communities, soil and site
information
Plant communities Soil and site data
Kade et al. 2005, Plant communities and soils in cryoturbated tundra
71. Patterned-ground features
Intermediate Ordination of zonal patterned
Between patterned-ground
features ground vegetation: controlling
environmental gradients
• NMDS ordination.
• Clear gradient of vegetation response to
cryoturbation within each subzone and
clear floristic separation between
subzones.
• But no clear overall controlling factors
for the whole data set.
• Floristic separation between Alaska and
Canada portions of the gradient due to
different floristic provinces, and
substrate differences.
Walker, D.A., Kuss, P., et al., 2011 (in revision), Vegetation and
patterned-ground relationships along the Arctic bioclimate gradient
72. Biomass for each relevé was used to develop
landscape-level biomass for each grid.
Raynolds, M.K., Walker, D.A., Munger, C.A., Vonlanthen, C.M., and Kade, A.N.a., 2008, A map analysis of patterned-ground
(Raynolds et al. 2008, JGR)
along a North American Arctic Transect: Journal of Geophysical Research - Biogeosciences, v. 113, p. 1-18.
73. To examine the insulative effect of vegetation:
n-factor was determined for each vegetation
type.
Loggers:
i-button data loggers 1. base of live vegetation
2. base of organic horizons
3. center of circle
vascular plant canopy
live moss mat
dead organic matter
Typical frost boil mineral soil
Tundra Circle Tundra
Kade, A., Romanovsky, V.E., and Walker, D.A., 2006, The N-factor of nonsorted circles along a climate gradient in Arctic
Alaska: Permafrost and Periglacial Processes, v. 17, p. 279-289.
74. n-factors for patterned- ground
n-factor: features along the NAAT
–Ratio of the degree-day total at the
soil surface to the degree-day total
of the air.
n = DDTsoil / DDTair
– Summer n factor uses thawing-
degree days.
– Winter n factor uses freezing-
degree days.
High Arctic: Mineral soil temperature
warmer than air temperature
because of radiative warming of
the soil surface.
Low Arctic: Interboil mineral-soil
temperatures are colder than air Walker, D.A., Kuss, P., et al., 2011 (in revision), Vegetation and
temperatures because of patterned-ground relationships along the Arctic bioclimate gradient
insulation of vegetation and in North America Applied Vegetation Science.
organic soil.
Winter: Soil temperatures much
warmer than air temperature,
particularly in Low Arctic because
of snow insulation.
75. Experimental alteration of vegetation canopy to examine
effects of vegetation on active layer and frost heave
Ph.D. project of Anja Kade
Control Vegetation Removal
Graminoid Transplants Moss Carpet Transplants
Response Variables: Frost Heave, Thaw Depth, Soil Moisture, Soil
Temperature
76. Hypothesized effects of Kade experiment
Kade and Walker, 2008, Arctic, Alpine and Antarctic Research
77. Effects of vegetation on summer and winter
soil surface temperatures.
Barren Mean Summer Temperature:
Summer Vegetation removal: +1.5˚C (+22%)
Control
Moss addition: -2.8 ˚C (-42%)
Mosses
Winter
Mean Winter Temperature:
Mosses
Control
Vegetation removal: -0.9˚C (-6%)
Moss addition: +1.3˚C (+7%)
Mosses
• The sedge treatment had a similar
response as the barren treatment.
Kade and Walker, 2008, Arctic, Alpine and Antarctic Research
78. Effects vegetation on thaw depth and heave
Maximum Thaw Depth
90.0000
Thaw depth (cm)
67.5000
45.0000 Thaw:
22.5000
Vegetation removal: +5 cm (+6%)
Moss addition: -11 cm (-14%)
0
Treatment Sedges Mosses Control
Frost Heave
16.0
Frost Heave
12.0
Heave (cm)
8.0 Heave:
4.0 Vegetation removal: +3 cm (+24%)
0
Moss addition: -5 cm (-40%)
Treatment Sedges Mosses Control
Kade and Walker, 2008, Arctic, Alpine and Antarctic Research
79. Soil moisture Vegetation and Snow/vegetation
Pattern insulation and
Environmental Climate/weather heave
Variables
Soil Physics Soil Chemistry
TMHM DFH
accurate heave pattern density
Models
WIT3D ARCVEG
liquid water vegetation
redistribution succession
vegetation pattern succession
Measured input and/or calibration data DFH: Differential Heave model
TMHM: Thermo Mechanical Heave Model
Simulated calibration and/or Input data
WIT3D: 3D Water Ice Temperature model
Feedback ARCVEG: Arctic Vegetation succession model
80. Differential frost heave (DFH) model of frost-heave
feature formation (Peterson and Krantz 2003)
• Heat preferentially escapes from the surface at high
points of small irregularities in the surface.
20 cm organic • These high points self-organize into patterns controlled
horizon
by mechanical properties of the soil (e.g., texture) and
active layer thickness.
• These high points are sites of increased ice-lens
development, and more heave.
Nonsorted
Inter-
circle
circle • Theoretically, non-sorted circles should be more closely
spaced in shallowly thawed soils.
Lenticular voids in soil created
by ice lenses.
Schematic of soil undergoing top-down
freezing. Ice lenses exist in the frozen
region and permafrost underlies the active
layer.
81. Modeling Components of the Project
• Differential Frost Heave (DFH) model (Peterson & Krantz):
Describes the self-organization of non-sorted circles in the absence
of vegetation. Models the process of differential frost heave and
spacing of frost features using linear instability analysis.
• Thermo-mechanical model (TMM) of frost heave (Nikolskiy et al.):
Detailed simulation of heaving process within a non-sorted circle
that includes mass, momentum and energy conservation laws for
water, ice, and soil. Accounts for the observation that heave is
considerably greater than can be accounted for by simply freezing
the amount of the water in the soil.
• WIT/ArcVeg (Daanen & Epstein): A 3-dimensional model of frost
heave. Mainly a hydrology-heave model driven by temperature
differentials and changes in vegetation patterns.
82. Vegetation Component
(Epstein, Walker et al.)
Linking
modeling
Mineralization
Soil Soil Recruitment
Organic Organic
efforts
Carbon Nitrogen
Climate Plant Carbon/ Resorption
Cryoturbation Nitrogen
Plant-Available
Nitrogen
N2-fixation N loss
Ice-lens Component Soil Component
(Krantz, Romanovsky, et al.) (Ping, Epstein et al.)
83. Differential Frost-Heave (DFH) Model
• The model
successfully
predicts order of
magnitude heave
and spacing of frost
boils.
• Other predictions Position of ground surface and Particle trajectories over
include effect of soil freezing fronts several hundred years
texture, air
temperature, snow
depth on magnitude
of heave.
Soil creep Time to stabilization
84.
Non-linear heat Liquid water balance
conduction equation
+ Equation
Soil particles conservation equation
Heat Flux
Active Layer
Ice Lenses (organic soil)
Seasonal frost
So chin
lea
il m g
Active Layer
ov
(mineral soil)
em
en
Water Flux
t&
Ice Lens Heave
Permafrost
Permafrost change over time
Nicolsky, D.J., Romanovsky, V.E., Tipenko, G.S., Walker, D.A. 2008. Modeling
biogeophysical interactions in nonsorted circles in the Low Arctic. Journal of Geophysical
85. The effect of insulation:
Themo-mechanical model of frost heave vegetation
interactions
0.18
Displacement of the ground surface • Each blue line
corresponds to the
0.16 No additional
insulation different depth of an
0.14 2cm additional insulation
0.12
layer over boil.
4cm
Heave (m)
0.1
6cm • The insulation
0.08 simulates the effect of
10cm vegetation cover on
0.06
frost heave.
0.04
0.02
• Thicker vegetation layer
causes better thermal
0
0 0.2 0.4 0.6 0.8 1 1.2 insulation and lowers
Distance from the center of a frost boil, m cryogenic suction,
hence the smaller frost
heave of the ground.
86. ArcVeg Model (Epstein et al. 2000)
CRYOTURBATION
C Mineralization Climate
CRYOTURBATION
Soil Soil Current PlantBiomass
Organic Organic Plant Attributes Recruitment Nutrient
Carbon Nitrogen Resorption
Senescence/
Mortality Plant Carbon /
Climate N Mineralization Nitrogen by
CRYOTURBATION N Immobilization Functional Type
Plant Uptake/ in Foliage, Roots
Growth and Wood
Plant-Available
Nitrogen Climate
Current Plant Biomass
Plant Attributes
N2-Fixation N loss
• Simulates the interannual dynamics of tundra plant community composition and biomass.
• Parameterized for up to 20 plant growth forms.
• Based on nitrogen mass balance among pools of soil organic and inorganic nitrogen, and
live plant nitrogen in live phytomass.
• Changes in temperature drive changes in net N mineralization and the length of the
growing season and thereby alter the community biomass and composition.
• Climate and disturbance are stochastic forcing variables.
87. Modeling WIT-ArcVeg
Random vegetation
Year 1
Organized vegetation
Year >1000
http://snowy.arsc.alaska.edu/WIT3D/
Daanen, R.P., Misra, D., Epstein, H., et al. 2008. Simulating nonsorted circle
development in arctic tundra ecosystems. Journal of Geophysical Research -
Biogeosciences. 113:1-10.
88. 3-D Modeling of patterned-ground formation
(R. Daanen, D. Misra, H. Epstein)
WIT3D/ArcVeg Model in ARSC Discovery Lab. Photo: Ronnie Daanen
89. Modeling did not address issue of cracking.
The formation of almost all nonsorted circles also
involve cracking!
We didn’t understand this until late in the project.
Scale
2m
Howe Island, AK Photo by Anja Kade
93. Components of landscape
modified by both cracking and
differential heave
Non-sorted polygon
35 cm
Non-sorted circle
90 cm
Medium non-
sorted polygon
200 cm
Large and small seasonal frost-crack non-sorted polygons,
Howe Island. Photo: Anja Kade
Large non-sorted permafrost crack polygons
(20-30 m diameter), Howe Island
Photo: D.A. Walker
94. New tools for looking at complexity of patterned ground
Ground-base LIDAR units for
detailed 3-D views of frost heave:
Daanen et al. 2010.
Has shown that the annual frost
can exceed 25 cm!
Frost cracking model:
Zhang et al. (in progress):
Has replicated horizontal
cracking observed at the top of
the permafrost table and could
help explain development of
intermediate layer.
95. Conceptual model
frost boils and earth
hummock formation
in relationship to
permafrost dynamics
Only model that invokes the
permafrost and cracking!
Others operate entirely in the
active layer.
Shur, Y., Jorgenson, T., Kanevskiy, M., and
Ping, C.-L., 2008, Formation of frost boils
and earth hummocks, in Kane, D.I., and
Hinkel, K.M., eds., Ninth Internaitonal
Conference on Permaforst, Fairbanks,
Institute of Northern Engineering,
University of Alaska Fairbanks, p.
96. High-resolution Quickbird imagery:
Deadhorse Biocomplexity Site
Reveal that small-scale patterned ground
features are nearly ubiquitous in Arctic
landscapes!
Vlad’s Deadhorse
climate station
Nonsorted circles covering much of
the image. Sizes about 2-4 m diameter.
98. Students both learned through a course offered by Bill
Gould and Grizelle Gonzalez and they worked with the
research team providing labor and insights and their own
research projects.
Photo: Heather Fuller
99. Conclusions
1. Patterned-ground morphology on zonal sites changes in predictable ways
with differences in climate, soil-moisture, soil-texture, and the structure of
the vegetation.
2. Contrasts in the vegetation on and between patterned-ground features is
best developed in Subzones C and D. These differences drive the
movement of heat and water and the development of frost heave.
3. Strong thermal, hydrological, and chemical gradients help to maintain the
position of these features in the same locality over long time periods.
4. Cryoturbation of organic material and aggrading permafrost tables act to
sequester large amounts of carbon within the permafrost of these
ecosystems.
5. Models have replicated the patterns related to frost heave (non-sorted
circles and earth hummocks). Contraction cracking will require new
models.
6. The presence of non-sorted circles strongly affect a wide variety of
ecosystem properties (soil temperatures, active-layer depths, carbon
storage, flux rates, biodiversity, successional pathways) and determine
how these systems respond to disturbances including climate change.
100. Synthesis of
biocomplexity project
9 Articles from the North
America transect:
Walker, D.A., Epstein, H.E., Romanovsky, V.E.,
Ping, C.L., Michaelson, G.J., Daanen, R.P.,
Shur, Y., Peterson, R.A., Krantz, W.B.,
Raynolds, M.K., Gould, W.A., Gonzalez, G.,
Nicolsky, D.J., Vonlanthen, C.M., Kade,
A.N., Kuss, P., Kelley, A.M., Munger, C.A.,
Tarnocai, C.T., Matveyeva, N.V., and
Daniëls, F.J.A., 2008, Arctic patterned-
ground ecosystems: A synthesis of field
studies and models along a North American
Arctic Transect: Journal of Geophysical
Research - Biogeosciences, v. 113, p.
G03S01.
102. Děkuji!
Funding and Support:
NSF Office of Polar Programs,
Grant No. OPP-0120736
International Arctic Research Center
VECO Polar Resources
Aurora Institute
Parks Canada
Inuvialuit Corp.
Institute of Arctic Biology, UAF
Participants in the Project:
Howard E. Epstein and Alexia Kelley (Department of Environmental Science, University of Virginia)
William A. Gould and Grizelle Gonzalez (International Institute of Tropical Forestry, USDA Forest Service)
William B. Krantz (Department of Chemical Engineering, University of Cincinnati)
Rorik A. Peterson (Geophysical Institute and Department of Geology and Geophysics, University of Alaska
Fairbanks)
Chien-Lu Ping and Gary Michaelson (Palmer Research Center, University of Alaska Fairbanks, Palmer, AK)
Skip Walker, Martha K. Raynolds, Hilmar Maier, Christine Martin, Anja N. Kade, Julie A. Knudson, Patrick
Kuss, Corinne Munger, Erin Cushing, Ronnie Daanan, Ina Timling (Alaska Geobotany Center, Institute
of Arctic Biology, University of Alaska Fairbanks)
Vladimir E. Romanovsky, Dimitri Nikolsky, and Gennadiy Tipenko (Geophysical Institute and Department of
Geology and Geophysics, University of Alaska Fairbanks)
Yuri Shur (Civil and Environmental Engineering Department, University of Alaska Fairbanks)
Charles Tarnocai (Agriculture and Agri-Food Canada, Ottawa, CA)
Students of Bill Gould’s Arctic Field Ecology Course (University of Minnesota)
Hinweis der Redaktion
This talk focus on factors that affect small patterned-ground forms and their interactions across a bioclimate gradient in northern Alaska and the western Canadian Arctic. \nThis is a collaborative effort by team members of an NSF-funded biocomplextiy project. \n
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This project focuses on frost-boil ecosystems. \n\nThe goal of the project is to better understand the complex linkages between frost heave, biogeochemical cycles, vegetation, disturbance, and climate across the full Arctic summer temperature gradient in order to better predict Arctic ecosystem responses to changing climate and land use.\n
Why focus on small patterned-ground features?\nThe processes involved in the formation of patterned-ground landscapes are not well understood.\n\nThe importance of patterned ground with respect to biogeochemical cycling, carbon sequestration and other ecosystem processes is poorly known. \n\nThey are an ideal natural system to to help predict the consequences of climate change of disturbed and undisturbed tundra. \n
Why focus on small patterned-ground features?\nThe processes involved in the formation of patterned-ground landscapes are not well understood.\n\nThe importance of patterned ground with respect to biogeochemical cycling, carbon sequestration and other ecosystem processes is poorly known. \n\nThey are an ideal natural system to to help predict the consequences of climate change of disturbed and undisturbed tundra. \n
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In summary, differential heave can cause a variety of non-sorted circle and hummock forms depending on the climate, soils, and the intensity of the vegetation action.\n
We first noticed that frost boils inter-graded with large hummocks, which have been called earth hummocks by Tarnocai and Zoltai. \n\nPeterson and Krantz recognized that hummocks had a similar origin to frost boils. In fact, their model was originally made to describe hummock formation and not formation of non-sorted circles.\n\nTwo things appear to lead to hummock formation. The first is an organic vegetation mat, that prevents the disturbance of soil by frost action. \n\nThe second is the presence of clay-rich soils, that restrict the soil from collapsing back to its original state when ice-lenses melt during the summer. \n\nWe also found that earth hummocks can occur in from Subzone B to Subzone E, but that they are most common in the south, where they are the predominant surface form. And are common even in forested areas. \n
The surface forms are subject to modifications by gravity, soil moisture, and the presence of rocky soils, which are outside the scope of this talk.\nBut: \nStripes often form on slopes. There are also many other forms that are created by slope processes. \n\nVery large non-sorted circles can form in wet silty soils of subzones C and D. These often have a ring of peat or tussocks around the perimeter of the circle.\n\nSorted circles commonly form in rocky soils.\n
In the High Arctic (Subzones A, B, and C), most surfaces with fine-grained soils have small polygons that are the result of contraction cracking.\n\nThere is some debate regarding whether or not the majority of these are caused by desiccation cracking or by frost cracking that is confined to the active layer.\n
Modification of small polygons occurs on slopes where erosion and eolian deposition modify the basic polygon forms resulting in turf hummocks, which have been described by Broll and Tarnocai (2003).\nThese features often are associated with snow beds and distinctive plant communities that form a tight turf.\n
In the High Arctic (Subzones A, B, and C), most surfaces with fine-grained soils have small polygons that are the result of contraction cracking.\n\nThere is some debate regarding whether or not the majority of these are caused by desiccation cracking or by frost cracking that is confined to the active layer.\n
My impression from the literature is that the prevailing view is that most of these small polygons are the result of desiccation cracking.\n\nWashburn states in his 1980 book that most fiine-scale (<1-m diameter) polygons are the result of desiccation cracking.\n\nI think that this statement needs to be re-evaluated, through experiments and models to see just what conditions are necessary for the formation of small polygons.\n\nThese features are ubiquitous on most High Arctic surfaces, in all soil textures and all moisture regimes. And they seem to have deeper cracking than soils that have obvious desiccation cracking.\n\nAnother factor suggesting that seasonal frost cracking is the cause of most of these features, is the lack of such features in non-permafrost cold desert areas outside of the Arctic.\n\nIt seems that these features are possibly a result of both processes, but that frost cracking initiates the process of polygon formation and then other processes of erosion, desiccation, and repeated frost cracking modify the original features. \n
Contraction cracking occurs at several scales. \nIn the upper left, ice-wedge polygons up to 20 m across are the result of permafrost cracking at very cold temperatures.\n\nWe have been discussing much smaller features the result from cracking within the active layer. As in the upper right. \n\nWithin these features, even smaller polygons form such as in the lower left. \n\nCracking at similar scales can even occur within cushions of vegetation as in the lower right, Suggesting that within a certain range of scales, frost cracking may be fractal. \n
Soil texture also strongly influences the form of the patterned ground features.\n\n Sorted circles form in rocky soils.\n Earth hummocks in clayey soils.\n Sorted circles without hummocks in silty soils.\n And sandy soils are generally featureless without circles or hummocks.\n
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In general:\nCircular forms are caused by differential heave resulting in circles and earth hummocks.\n\nPolygonal forms are caused by cracking (thermal or desiccation):\nLarge polygons (thermal contraction cracking penetrates deep into the permafrost)\nSmall non-sorted polygons (contraction cracking confined to zone of seasonal thaw)\n\nBoth differential heave and cracking can occur at a variety of scales forming complex landscape patterns.\n\nThe forms can be modified by a wide variety of processes including sorting (sorted forms), erosion and eolian deposition (turf hummocks, high-centered polygons), down-slope soil movement (stripes and lobes).\n
The project initially focused on frost boils and spotted tundra. \n\nThese features are caused by differential frost heave. \n\nTheir formation has been modelled by Peterson and Krantz.\n\nThese features have a variety of names including: \nNon-sorted circles (Washburn 1980) \n &#x2018;Frost medalllions&#x2019; (Russian term), \n &#x2018;Mud boil&#x2019; (Zoltai and Tarnocai 1981) \n &#x2018;Frost scar&#x2019; (Everett 1966)\n &#x2018;Spotted tundra&#x2019; (pyatnistye tundry, (Dostoyalov and Kudravstev 1967).\n\nFor the remainder of this talk, I will refer to these features as nonsorted circles in conformance with the terminology of Washburn.\n
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The central questions are:. \nHow do biological and physical processes interact to form the patterned ground ecosystems?\n\nHow do these systems change across the Arctic climate gradient?\n\n\nTheir formation has been modelled by Peterson and Krantz.\n\nThese features have a variety of names including: \nNon-sorted circles (Washburn 1980) \n &#x2018;Frost medalllions&#x2019; (Russian term), \n &#x2018;Mud boil&#x2019; (Zoltai and Tarnocai 1981) \n &#x2018;Frost scar&#x2019; (Everett 1966)\n &#x2018;Spotted tundra&#x2019; (pyatnistye tundry, (Dostoyalov and Kudravstev 1967).\n\nFor the remainder of this talk, I will refer to these features as nonsorted circles in conformance with the terminology of Washburn.\n
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In our study, we are examining how these feature change across the arctic climate gradient in conjunction with climate and differences in vegetation. \n\nThis map shows the five bioclimate subzones of the Arctic vegetation Zone as described on the Circumpolar Arctic Vegetation Map.\n\nEach subzone is defined on the basis of a combination of climate and dominant vegetation. \n\nSubzone A is the coldest with a mean July temperature between 2 and 3 degrees C, and Subzone E is the warmest with mean July temperatures between 9 and 12 degrees C.\n
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Ken Borek Air Ltd. Was the company that rescued Dr. Jerri Nielsen from the South Pole a few years ago, when she realized she had breast cancer during the Antarctic winter.\n
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Differential frost heave occurs because soils do not uniformily freeze from top to bottom. Some areas form more ice-lenses than others.\n\nThe processes involved in differential frost heave have been described in a model by Peterson and Krantz (2003)\nVery briefly: Briefly: \n\n Heat preferentially escapes from the surface at high points of small irregularities in the surface. \n\n These high points self-organize into patterns controlled by mechanical properties of the soil (e.g., texture) and active layer thickness.\n\n These high points are sites of increased heat and water flux, ice-lens development, and more heave. Water is pulled to the site of freezing by cryostatic suction.\n
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Plant cover:\nInsulates the surface decreasing the heat flux and summer soil temperatures.\nstabilizes cryoturbation and limits needle-ice formation.\nPromotes nitrogen and carbon inputs to the soil.\n\nThe effect of vegetation on patterned ground morphology increases toward the south.\n
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The results showed as exoected, the vegetation strongly affects the soil surface temperatures.\nMean summer soil temperatures increased 1.5&#x2DA;C by vegetation removal and decreased 2.8&#x2DA;C by the addition of moss. \nMean winter soil temperatures decreased 0.9&#x2DA;C by vegetation removal and increased 1.3&#x2DA;C by the addition of moss.\nThe sedge treatment had a similar response as the barren treatment.\n
The differences in temperature had major effects on thaw depth and frost heave.\nThaw increased 5 cm with removal of vegetation and decreased 11 cm with addition of moss. \nHeave increased 3 cm with removal of vegetation and decreased 7 cm with addition of moss.\n
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The upper photo shows two soil plugs taken from a nonsorted circel (right) and an area in between two circles (left). \n\nThe lenticular voids that are evident in both soils are formed by ice lenses that form during the winter.\n\nThe model of Peterson and Krantz describes the formation of these lenses.\n\nVery briefly the model assumes homogeneous initial conditions in a silty soil that is prone to ice-lens formation.\n\nHeat preferentially escapes from the surface at high points of small irregularities in the surface. \n\n These high points self-organize into patterns controlled by mechanical properties of the soil (e.g., texture) and active layer thickness.\n\n These high points are sites of increased ice-lens development, and more heave. \n\n Theoretically, non-sorted circles should be more closely spaced in shallowly thawed soils.\n
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\nThe ArcVeg model will pass to the DFH model the total live phytomass by plant type and the total soil organic matter.&#xAF;&#xAF;\n
Quote from Bill Krantz: email 25 Aug 2003: \nThe DFH is very complex to model because of the vastly different scales of the various physical phenomena that must be incorporated into a viable model. The heat transfer occurs over the largest scale, namely the depth of the active layer, about one meter or so. However, the frost heave arises because the micron-scale pores in the particulate soil are preferentially wet by liquid water rather than by ice. Hence, freezing occurs on the micron scale in the pores, in involves a core of ice penetrating the center of a pore; the gap between the pore wall and this core of ice is occupied by unfrozen water. As the freezing soil becomes progressively colder, the ice core becomes thicker and the thin film of unfrozen water becomes thinner. When this film of unfrozen water thins to the scale of the long-range molecular dispersion forces (around 0.1 micron), the pressure tensor become anisotropic; that is the pressure in the direction parallel to the pore wall becomes less than the pressure perpendicular to the pore wall. This causes a suction (cryostatic suction) to be generated that pulls unfrozen water up from the water table thereby causing significantly more frost heave than can occur by just freezing the water in the soil. So far, we have three scales: the scale of the active layer (1 meter); the scale of the pore diameter in the soil (a few microns); and the scale for generating cryostatic suction (submicron). Yet there is another scale, namely that of differential frost heave: I.e., the diameter of the frost boils or hummocks. The scale is determined by a balance between nature wanting to make the corrugation or wavelength that characterizes the spacing between frost boils or hummocks as short as possible to permit more heat transfer and thereby more freezing, and the counter tendency of nature to avoid trying to bend a layer of frozen soil too much. Hence, what happens is compromise between nature trying to choose a short length scale to gie a lot surface area for hat transfer and long length scale to minimize the energy required to bend frozen soil. Believe it or not, the DFH model incorporates the physics occurring on all these scales! Now if that is not enough scales for you I suggest that you visit a fish market!\n\nI forgot to mention yet another scale that we incorporate into the DFH model. Although the heat transfer occurs over the longest length scale of the active layer depth, all the ice formation essentially occurs within the frozen fringe that is only a centimeter or so in thickness! One of the really difficult problems that we had to handle mathematically in the model was how to incorporate the physics of the frozen fringe. It is important to mention this centimeter length scale as well in your overview.\n\nOh, I forgot to mention yet another scale that we incorporate in the DFH model. Although the heat transfer occur over the longest length scale of the active layer depth, all the ice formation essentially occurs within the frozen fringe that is only a centimeter or so in thickness! One of the really difficult problems that we to handle mathematically in the model was how to incorporate the physics of the frozen fringe. \n
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ArcVeg simulates the interannual dynamics of tundra plant community composition and biomass based on nitrogen mass balance among pools of soil organic and inorganic nitrogen, and live plant nitrogen in live phytomass. \n Changes in temperature drive changes in net N mineralization and the length of the growing season and thereby alter the community biomass and composition. \n Climate and disturbance are stochastic forcing variables.\nThe DFH model will provide for ArcVeg the spatial frequencies of frost boil disturbances.\n Spatial and temporal dynamics of cryoturbation will influence the tundra system in ArcVeg through vegetation mortality and direct and indirect effects on soil nitrogen.\n
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In the High Arctic contraction cracking interacts with differential frost heave.\n\nThis remarkable photo was taken by Anja Kade at Howe Island, from an elevation of about 30 m above a field of nonsorted circles.\n\nThe scale bar shows the diameter of the features.\n
The smaller features are small non-sorted seasonal frost-crack polygons about 35 to 50 cm in diameter.\n
The white areas are nearly barren frost-heave non-sorted circles 90 to 200 cm in diameter.\n
Differential heave also appears to have aggregated the small non-sorted polygons into larger features that are 200 to 300 cm across.\n
This schematic summarizes the main components of the landscape. There are also much larger non-sorted ice-wedge polygons that enclose the entire field.\n\nThe aggregation of the small polygons into larger polygons by frost heave is fairly common, but vegetation often masks the smaller polygons particularly in more southern sites.\n
