Transcript Landscape pattern - higher level constraints

LANDSCAPE PATTERNHIGHER LEVEL
CONSTRAINTS
Recall from hierarchy topic reading that at
different levels in a hierarchy, a variable
influencing a process at a focal level may or
may not change, but a shift in relative
importance of variables occurs
• Level of focus
constrained by higher
level variables
• Lower level variables
often explanatory
• E.g., leaf litter
decomposition from
last week.
• (What is constraint?
What are explanatory
components?)
From Turner, Gardner, and O’Neill 2001
From Urban et al. 1987
Climate definition -- composite, long-term
weather of a region, that acts as the primary
control for ecosystem distribution as source of
energy and water (Bailey 1995).
• Response to latitude - variation in solar energycontrols both temperature and moisture distribution.
• Different temporal scale than weather, e.g., daily
fluctuations
Higher spatial level than microclimate, e.g., N and S
sides of hill
From Bailey 1998
CLIMATIC REGIME - pattern of diurnal
and seasonal fluxes of energy and moisture.
LANDFORM - Next level down
in hierarchy of constraints
• Modifies, is modified by, climate
• Provide the template for disturbance and
biotic responses.
Swanson et al. (1988) - role of landforms
and geomorphic processes in structuring
landscapes
From Bailey 1998
Climate and landform interact at all scales
(continental to landscape to site).
• Because elevation, aspect, and surface
texture interrupt air masses, influence
energy input from sunlight, and
precipitation.
(e.g., Greater insolation on south slopes
causes warmer sites, greater
evapotranspiration).
From Bailey 1998
• (e.g., Elevation can cause rain shadow effect in
rugged terrain.)
From Bailey 1998
(e.g., Elevation can cause rain shadow effect
in rugged terrain.)
From Bailey 1998
Landforms interact with climate,
increase, decrease susceptibility to
disturbance. (Constraining lower
levels).
• e.g., sheltering/exposing forest to
windthrow,
• greater vulnerability of ridges to fire
ignition, or
• barriers to fire spread.
• Landforms also play role in water
movement and concentration, and soil
development differences.
• Topography and gravitational movement of
water, and evapotranspiration create a
toposequence or catena of soils.
- Weathering of rock and movement of particles
down slope results in deeper, finer textured soils.
- Greater water holding capacity; productivity.
- Greater organic matter development, movement
down, continues to build soil.
From Bailey 1998
Climate controls biota, soils,
resulting ecosystem pattern
From Bailey 1998
Climate controls several large
scale processes •
•
•
•
Hydrologic cycle
Landforms and erosion cycles
Plant/animal life cycles and distributions
Fire and wind disturbance regimes
Hydrologic cycle
• Pattern of precipitation and
evapotranspiration.
• e.g., pattern of annual streamflow varies in
diff. climate regions depending on
seasonality of precipitation, temperature,
evaporation, transpiration by plants.
Landforms and erosion cycles
• e.g., Erosion rates vary with rock type, but
also whether climate supports soil
development, adequate moisture for
vegetative cover.
Plant/animal life cycles and
biogeographic distribution
• Life cycles - e.g., periods of activity,
dormancy, reproduction, adjust to seasonal
patterns of precipitation/moisture
Fire and wind disturbance
regimes
• e.g., amount of plant productivity,
frequency and seasonality of dryness
influence type of fire regime.
• Western ponderosa pine - frequent, low
intensity ground fires, trees survive.
• e.g., boreal forest - infrequent fires, but
intense, crown fires, stand initiating.
• Whittaker (1952, 1953) sampled
vegetation across a range of montane
habitats, spanning elevation and aspect
differences; microclimatic- landform
controlled.
• Found that species responded
individualistically to changing
environment.
• But communities could be discerned
within environmental space defined by
elevational and aspect gradients.
From Whittaker 1956
• Similar to what John Curtis and students
were doing here at same time across S.
Wisconsin.
• Not strong topographic gradient here, but
sites along moisture/nutrient gradient.
Neilson et al. series of papers (1983,
1986, 1987, 1992)- examined largescale regional and continental climate
data spatially and temporally.
• Used weather station transects across U.S.
and major biomes with characteristic
composition and physiognomy.
• Plotted monthly 30 yr. mean temperature and
precipitation.
Converted to contour diagrams.
From Neilson et al. 1992
From Neilson et al. 1992
From Neilson et al. 1992
Stephenson (1990) described past
studies using annual energy
(temperature) and precipitation to
relate climate to vegetation
• Either directly, or indirectly through ratios
• Relate climate to vegetation formations
(physiognomy- plant growth form, e.g.,
graminoid, shrub, trees- needle-leaved
evergreen vs. broad-leaved deciduous.
• Many used potential evapotranspiration• Given climate and energy (annual temp.)
available at a site, evaporative water loss
assuming complete plant cover and unlimited
water available.
• Assumes temp. and precip. independentdoes not distinguish well between climates
with similar annual energy and moisture, but
different seasonal distribution.
– e.g., PNW and NE U.S.- similar, but
different vegetation.
- Stephenson used WATER BALANCEactual evapotranspiration and deficit.
• ACTUAL EVAPOTRANSPIRATIONevaporative loss with prevailing energy
and available, not unlimited, water.
and DEFICIT (diff. of potential and
actual evapotranspiration).
• Climate as sensed by plants- interaction of
energy and water in the environment.
From Stevenson 1990
• Below large scale geomorphology or
landform levels,
• Landscape position has been shown to be
important in causing pattern in many
different systems, many systems with
relatively little relief.
• Lakes in a toposequence in northern
Wisconsin (Kratz et al. 1991).
• Great Plains grasslands (Sala et al. 1988;
Woodmansee 1990 in Zonneveld and
Forman;
• Arctic tundra terrestrial
toposequenceShaver et al. in Turner and
Gardner 1991).
• Bogs and patterned peatlands in cool
temperate regions are another example of a
large, complex landscape system that is
controlled by close climate and landform
interaction, with a major role played by
above and below ground hydrology.
• Most simply, small bogs are wetlands. Like
other wetlands- within upland matrix- water
table at or near surface.
• Landform controlled at this simple level,
assuming relatively constant climate.
Larger peatland landscapes can
be very complex
Large areas- matrix. Cool wet climate, low
evapotranspiration.
• Flat or slightly sloping, poor substrate
permeability.
• Low oxygen, decomposition- peat
accumulation.
• Can also occur on steeply sloping
landforms, under right climate.
• Ombrotrophic bogs - low pH, largely on
woody peat, low nutrient availability,
largely atmospheric inputs of water and
nutrients.
• Minertrophic bogs or fens - groundwater
inputs, higher nutrient avail. and pH.
• Large differences on within-peatland
formations, species composition.
From Glaser
• David Foster found similar patterns in Labrador
peatlands, as well as biological mechanisms
responsible for development of finer scale patterns
of open water over time, within the bog
vegetation.
• This finer scale pattern was different than that
in Minnesota.
• Presumably because of greater seasonal drying
in Minnesota which affects an entire flat peatland.
• More constant moisture in Labrador allows
development of finer-scale heterogeneity caused
by differential peat accumulation and vegetation
degradation.
• Foster and King (1986) studied forest
vegetation pattern in Labrador, looking at
climate and landform interactions.
• Studied fire and physiography role in
distribution of paper birch forest patches
within matrix of spruce-fir.
• Found nearly all birch forest patches on
steep slopes of ridges with high moisture.
Figure 4.6 Distribution of Betula papyrifera forests (black) on the hillslopes and canyon walls of the St. Augustine
River Valley, southeast Labrador. Adapted from Foster and King 1986.
From Turner, Gardner, and O’Neill 2001
• Foster and Boose (1992)- related study in New
England used GIS to analyze correlates of severe
hurricane damage to forests.
• Found slope and aspect highly correlated with
increasing damage.
• As well as tree height and species composition.
• Damaged stands 3% in topographically protected
sites, 31% intermediate, 66% exposed.
• Damage increased linearly with tree height.
• Eric Grimm (1984) studied Big Woods of
SE Minnesota
• Region of mesic forest within oak/prairie
transition
• Historically puzzling location for elm,
maple, basswood
• Found no correlation of pre-European
vegetation with climate gradient
• Landform (fire breaks), and soils most
important.
We will look in more detail at research examining
ecosystem processes that relate to landscape and
landform pattern a little later in the course.
From Bailey 1998