Physiography & Soils Flashcards
What is physiography?
physical geography
the study of the form and substance of the surface features of a region (the abiotic features)
including
what the abiotic features of a terrestrial environment are and how they shape the environment’s biotic communities
and how it shapes ecosystem composition, structure and function
What are the 3 characteristics of physiography?
setting (glacial vs. not glaciated, coastal vs. inland)
specific landforms (elevation, size, form, parent material, slope)
position of the landform on the landscape (elevation, proximity)
What other features can shape the biotic community aside from the main 3 physiographic ones?
soil type and characteristics
disturbance events (type, frequency, severity)
human modification of landscape or biotic features
How has physiographic setting shaped landscapes in Canada and BC?
glaciation has had strong influence on physiography as most of the province was glaciated with some refugia
these glaciations and then subsequent retreating has modified the landscape and caused many gradients of elevation across the province and country (ex. looking at a cross section of the province, there’s huge variation in physiographic regions from the coast to the strait of Georgia, to the coast mountains, to the interior plateaus, to the Cassiar-Columbias, to the Rocky Mtn Trench, to the Rockies, and the Great Plains in Alberta
What are considered major physiogeographic regions in BC?
the mountains
ex.
coastline
Insular mountains
Strait of Georgia depression
Coast Mountains
Interior plateaus (Fraser Valley, Okanagan)
Cassiar-Columbia mountains
Rocky Mountain Trench
Rockies
What are some examples across Canada of past glacial activity creating unique landscape features?
Champlain Sea - past glaciers suppressed the land and created an inland sea from the Atlantic Ocean in Southern Ontario and Quebec - contains different soils and topography from surrounding area
Oak Ridges Moraine - dense (200m) glacial deposits in Southern Ontario has become a large aquifer and headwaters for a lot of rivers
What are some examples of coastal landforms (physiography)?
coastal lagoon
coastal dunes
brackish river estuary
cliffs
sea arches
beaches
sea stacks
sea stumps
mangroves
lagoons
What shapes shorelines?
sediment deposits from land and erosion by waves
sea level changes (isostatic rebound)
What is isostatic rebound?
when land masses rise that were depressed by glaciers after glacial retreat
What are examples of specific landforms in BC?
ranges from continental to regional/local
continental = mountain ranges (ex. coastal mountains) and plains (ex. Central Plateau), river basins (ex. Fraser River)
What major influence do landforms have?
they can influence ecosystem characteristics
ex. mountains create rainshadows
What 5 things does the influence of local landforms depend on?
elevation
size
form
slope
parent material
Will influences of elevation be more regional or continental?
regional
Describe how Interior Fraser-Thompson Plateau is an example of how elevation can create varied landscapes
this region has 84 peaks with elevation up to 2334 m
this is a highly varied landscape that includes a variety of forest types
What kind of BEC zones are heavily influenced by elevation?
Engelmann Spruce-Subalpine fir
Montane Spruce
Alpine tundra (BAFA, CMA, IMA)
How does elevation effect MAT? MAP?
Lower MAT with increasing elevation
higher MAP with increasing elevation and potential leeward rainshadows created
How is growing season effected by elevation?
shorter growing season with increasing elevation - soil temperatures decrease = low NPP
How does elevation effect productivity?
decreases productivity with increasing elevation
it limits plant establishment, growth and species composition - lower temperatures and higher ppt
How does size of landform effect the landscape?
the effects can vary massively depending on the size, incline, aspect, and elevation
What is an example of a BC small mountain range that has different landscapes/ habitat on either side of the range?
Strathcona Park - Landslide Lake vs Mt Colonel Foster
Use Mount Doug as an example for how aspect of landform size (even if landform is small) has an effect on the landscape
Mount Doug, though small, has 2 unique habitats on it depending on the side of the mountain
the south side is drier, thin soil, with little trees
the north side is wetter and dominated by WRC and Df
T or F: landform size can cause significant changes to climate and growing conditions
true
What are some examples of how microtopography can change growing conditions?
even minor changes to elevation - ex. forest floor vs the top of a log will support different biota
windthrow create different conditions = opens forest canopy
nurse logs colonized by other organisms in CDF - create habitat
changes soil conditions = change plant community structure
What landforms are considered level terrain?
plains, plateaus, river terraces, old lake beds, prairies
What usually forms / shapes level landforms?
water, but sometimes glacial activity like till deposits
How does water influence the effects on the landscape of level landforms?
1 - if there is little lateral movement of water, then water may rapidly drain into subsoil if there’s coarse parent material
2 - if soil drainage is poor (too compact, fine textured, bedrock) water will accumulate - can create bogs, lakes, marshes
both rapid drainage and slow drainage will change the plant community
What is an example of a level terrain with large water influence?
Tow Hill Ecological Reserve in Haida Gwaii has a peat bog adjacent to a beach/shore habitat
- the peat bog is a flat landform with poor drainage
Boreal forest wetlands and peat bogs
How does sloping terrain effect the landscape?
because it allows the lateral movement of water on the surface (or below), depending on the steepness of slope and shape of the slope, it can have dramatic impact on plant community
What are the 3 shapes of a slope? How do they influence how water moves across a landscape?
planar - no curves /\
- water will run right down slopes and pool at bottom = dry at top, wet at bottom and erosion higher
convex - ()
- the higher elevation parts are less steep
- more water might pool here
- water will run quickly down the rest of the slope - but maybe less water (less erosion)
concave - )(
- water will run quickly down the slope and pool at the bottom
- probably high erosion at the top
What features change the level of effect slopes have on the landscape?
slope form (planar, convex, concave)
slope aspect (North vs. South)
slope inclination (steepness)
slope length
What is slope aspect?
the direction of a slope face (N, E, S, W)
How does slope aspect change the landscape?
depending on its direction, a slope face will recieve different levels of sun exposure = affects temperature and precipitation
ex. south-facing typically receive more direct sunlight = drier, warmer
T or F: the effects of slope aspect are the same regardless of latitude
false, latitudes further from the equator experience slope aspect differences more greatly
because the sun hits the earth’s surface at increasingly different angles moving away from the equator (consider tropical vs. boreal)
Use the boreal forest to describe the effects of slope aspect at increasing latitudes
boreal slopes (high latitude) facing north are less productive and usually covered in permafrost because they receive so little direct sunlight = low activity in soils
soil has deeper active layers and warmer temperatures on south facing slopes = higher diversity of plants
How does east-west aspect affect plant community?
air temperature
east-facing slopes receive early morning sunlight when temperature is still cool and moisture is higher
west facing slopes receive hotter afternoon sun - temperature higher and drier
Give an example of a latitude and a forest that have more productive north-east facing slopes?
Appalachian mountains (mid-latitude east coast)
What is a site index?
the measure of potential site productivity (higher index = better growth)
How does slope inclination effect landscape?
the steepness of a slope will influence the amount of water available, the drainage, and accumulation of OM and nutrients
steeper = more water and nutrient run-off
How does slope length effect landscape?
the relationship to inclination will change the gradient of conditions
ex. short and steep will be very different from long and gentle
Describe the conditions on higher positions on slopes
drier = more drainage + sun + winds
usually less soil, OM and soil nutrients
Describe the conditions on lower positions on slopes
less windy and less sunny usually due to more shelter = wetter and cooler
usually more OM, soil and soil nutrients than at the top of a slopei
in what latitudes does slope position become more important?
higher latitudes where there’s shorter growing periods
What influences soil development and quality?
physiographic conditions + soil biota
Why are soils so important to forest ecosystems?
they are the foundation of terrestrial ecosystems and they contain complex abiotic and biotic components
Describe soil
material that develops naturally and is composed of loose mineral components and organic matter component
exists in all terrestrial ecosystems in varying quantities
supports microbiota and macrobiota that help develop soil composition, nutrient levels and complexity
a growth medium that responds to abiotic and biotic components
What does it mean that soil is a growth medium?
- habitat for microbes
- substrate for plants
- source of water and nutrients for plants
- both direct and indirect food source for animals
- resource bank for forest biota
- influences local microclimate
what 5 factors contribute to soil formation?
parent material - mineral contribution
topography/relief - shape of landscape
climate - temperature, ppt, wind
biota - micro and macro
time (geological)
How are parent material classified?
on how they were formed or scattered
What are the 7 classifications of parent material?
describe them and what their soils are like
- residual - bedrock that was weathered in place (non-glaciated) = soil resembles PM
- fluvial - sediments deposited from flowing water = soils often well-sorted (of similar size) sand and gravel
- glacial till - sediments deposited beneath, within, on top of glacial ice = soils poorly sorted mix of gravel, sand, silt, clay
- eolian: sediments moved and deposited by wind = soils usually well-sorted sand and silt (loess)
- colluvial - sediments moved by unchannelized flow on slope (gravity/not rivers) = soils resemble sediments from origin
- marine - sediments deposited on ocean floor are exposed from isostatic rebound
- lacustrine - PM sediment deposited in lakes = soils usually well sorted sand, silt, clay
What is another soil ‘parent material’ that is not mineral based?
organic matter - not derived from actual parent material but from plant and animal activity and matter
What is/are the parent materials for Canada’s soils? explain
most are of glacial origin because most of Canada’s land mass was exposed after the last glacial episode
t or f: Canada’s soils are old (geologically)
false, they are geologically young - most of the land was only exposed after the last Ice Age
How does the topography/relief of the land surface influence soil? (ie., what factors influence soil development?)
shape of landscape influences flow and distribution of water - erosion or accumulation
slope, aspect and elevation will influence plant growth and soil development
latitude and temperature during growing season will influence soil develppment
Will low lying sites have soils developing faster or slower? why?
quicker because they will have more moisture (less lateral movement of water) and less erosion (less sloping)
How does climate influence soil development?
climate influences the amount and type of ppt
the intensity of which may affect erosion in a site as well as the freeze-thaw processes
soil dispersal by wind or water is influenced by climate
How do soil micro- and macrobiomes influence soil?
plants hold parent material in place with their roots = contribute to water holding capacity of soil
plant roots are associated with microbiota that influence weathering of PM and release of minerals (P and N) to soil (usually a root symbiosis)
plant growth becomes OM in the soil = OM increases soil moisture and nutrient content, improving tolerance to variable abiotic conditions - also moderates microclimate
Rank sand, silt, clay in order of largest to smallest particle size (including units)
diameters
sand: 2-0.05 (from very coarse-very fine)
silt: 0.05-0.002
clay: =< 0.002 mm
What determines soil texture classes?
the relative proportions of different-sized particles (sand, silt, clay)
Define soil aggregates
the arrangement of small/individual soil particles of sand, silt, or clay to form larger particles
(chunks)
What helps stabilize and bind soil aggregates?
organic matter
What key soil conditions does soil structure influence?
water movement ability - water holding capacity
aeration
resistance to erosion
Which soil particle type/size are best at holding water? why?
clay because they have hydrostatic attraction (their negative anions attract and hold positive water cations tightly)
Describe flocculation
the process by which individual clay particles aggregate into larger chunks - usually associated with water
What are the classes of soil macro-aggregates?
granular
blocky
prismatic
columnar
platy
single grained
all of which are found in different soil horizon areas
Describe soil porosity
the distribution of aerated space in soils
How does soil porosity influence soil?
the amount of available space in soil influences the movement of water and gases (O2)
different soil macro-aggregates have different porosity
What % of pore space does a well-structured soil have?
65% pore space
Which macro-aggregate type would be the most porous? the least?
most would be single-grained or granular (mostly sand)
then blocky and prismatic
least would be platy and massive (layered like sediments basically - mostly clay)
Define soil consistency and explain the concept relating to its function
the physical resilience of soil
the stickiness of soil relates to its ability to resist deformation under stress
What factors does soil consistency influence?
soil stability and erodibility (resilience to stress) and resistance to compaction
What is the bulk density of soil? why is this measurement important?
the oven-dry weight of soil/unit of volume (g/cm^3)
this measurement reveals information about structure, texture, porosity, and OM content
What does a high bulk density indicate for soil?
more soil compaction
Define aeration in soil - what influences it?
gas exchange in soil
influenced by soil porosity and the distribution of pore space v. water spaces
What is the range of ideal bulk density for plant growth across all soil textures?
from < 1.10 g/cm^3 for clays to < 1.60 for sands and loamy sands
What abiotic and biotic factors determine soil temperature?
abiotic:
latitude
aspect
elevation
continentality
soil water content
soil texture
soil porosity
biotic:
vegetation cover
What does soil temperature effect?
many biological functions in the soil such as
root growth of plants
soil organism metabolism
decomposition rates
nutrient and water uptake
