Lec 6 - Ch 11, 12
Ch 11 - Terrestrial Flora/Fauna
•geographer looks for patterns in distribution
•what’s the distribution?
•why is it the way that it is?
I. Natural distributions
•4 conditions control:
•evolution
•migration
•reproduction
•extinction
A. Evolutionary development
•some species evolve from single original location; others may have evolved at
different locations
B. Migration
•both plants and animals can migrate
•current distribution can reflect a history of migration from a source or sources
•Fig 11-3
Cattle egrets -
•example of recent migration to South America/N America
•didn’t migrate until cattle began to be raised in S America
Coconut palm -
•float over great distances, then roots on new shore Fig 11-4
Reproductive success
•critical to success
•variety of factors that contribute
•may be the single most important factor in which population wins out when in
competition
Extinction
•small adjustments in local areas to mass extinctions of huge numbers of
species all over the planet (end of Cretaceous - huge extinction killed off
dinosaurs, many other species)
•example of common occurrence in local areas is plant succession - lake
example in text:
•transition from lake to marsh to meadow to forest as sediments fill up the lake
II. Terrestrial Flora
•Of interest for several reasons:
•big component of landscape
•sensitive environmental indicator
•influence on human activity
A. Characteristics
hardy and adaptable due to root systems below ground
•types
•perennials - survive year round
•annuals - die during winter, but germinate in spring
B. Adaptation mechanisms
2 types - xerophytic plants tolerate dry conds
hygrophytic plants tolerate wet conds
xerophytic characs:
•roots seek moisture
•stems store moisture (succulents like cacti)
•leaves lower the transpiration rate
•reproduction tied to precip, not an annual cycle
Hygrophytic characs -
•immersed in or frequently soaked with water
•also with extensive root systems or pliable stems
C. competition also a factor in survival - some species share common
environment, one may “win out” over others
D. Terminology for plants:
first break:
•plants with spores
•plants with seeds
•spores:
•bryophytes - mosses
•pteridophytes - ferns
•seeds
•gymnosperms - naked seeds, as in conifers
•angiosperms - protected seeds, as in flowering plants,deciduous trees
•other common terminology too…Fig 11-9
E. Spatial groupings
general drive toward “floristic stability”, usu toward taller plants, stable species
Major associations Fig 11-10
•Forest - overlapping canopy
•woodland - tree-dominated
•shrubland - woody plants (shrubs)
•grasslands savanna - low lat tall grass
•
prairie - mid lat tall grass
•
steppe - mid lat short grass
•desert - scattered plants, much bare ground; variety of vegetation
•tundra - high lats, grass, shrubs, no trees
•wetlands - standing water most of year swamps with trees
•
marshes with grasses
Vertical zonation
•similar effect to latitude changes: example of maximum treeline Fig 1114
III. Terrestrial Fauna (animals)
much greater variety than plants, harder to relate specifically to environments
•animals less prominent than plants - don’t stand out
•environmental relationships not clear - animals can move around, harder to
study
A. Characteristics of animals
2 universal characteristics, but sometimes hard to recognize:
1. Motile (self-generated mvmt)
2. Must eat - can’t manufacture their own food
B. Environmental adaptation - several types
1.Physiological
Example of physical adaptation to environment - fox ears small and large,
depending upon cooling needs in arctic or desert climate Fig 11-17
Other examples include:
webbed feet for swimming
fur for the cold
add’l glands for sweating/evaporative cooling
2. Behavioral adaptation
•migration
•hibernation
•nocturnal activity
•estivation
3. Reproductive
•changes in cycles
•changes in nesting
•geared toward more survival of young
C. Competition
•rivalry for space
•predation
D. Cooperation
•several forms of symbiosis:
•mutualism, commensalism, parasitism
Symbiosis types:
•mutualism - mutually beneficial
•commensalism - no harm but not necessarily a benefit
•parasitism - parasite benefits, host is harmed
E. kinds of animals
first break: invertebrates vs vertebrates Fig 11-20 shows relative abundance
•invertebrates - no backbone - more than 90% of all species
•vertebrates - backbone
5 main groups of vertebrates:
•fishes - breathe under water
•amphibians - semiaquatic; gills as young, lungs as adults
•reptiles - mostly land-based
•birds - perhaps evolved from reptiles, but constant body temperature
•mammals - several unique features
•produce milk for the young
•have real hair
•constant body temperature
•placental vs marsupials
•2 primitive mammals are actually egg-layers!
•Echidna below
duck-billed platypus
Zoogeographic regions Fig 11-24 variability in faunal diversity around world
IV. Major Biomes of the World Fig 11-26
compare w/ Fig 8-5 - note relationships to climatic regions
Chap 12 - Soils
now to the lithosphere - seems to be stable and non-changing
not true, but things take a long time to change
rest of book devoted to this “sphere”
this chap we deal with soils….lots of new terminology
I. Soil and regolith
•why important? “all terrestrial life nurtured here”
•complex assemblage of
•minerals,
•organic matter,
•life
•gas & liquid sol’ns
•we think of it mostly as harboring plant growth - a thin skin over rock that can
support life
•extends to base of plant root systems
•soil formation begins as weathering of rock (big pieces to little pieces) which
results in layer of regolith (“blanket rock”)
•above the regolith occurs the soil, which contains even smaller mineral pieces
and also organic material, air , and water
II. Soil Forming factors
2 main types of factors
•active
•climate action
•biological action
•passive
•geology
•topography
•time (Passive? What do you think?)
II soil formation factors (cont)
A.geologic factor
•as parent material, exerts major control over end-product
•chemical composition
•physical characteristics
•fine texture (shale) vs coarse texture (sand) produces diff
soils
•example - texture influences air & water penetration
•over time, parent factor diminishes as other processes take hold
•ultimately, may be impossible to tell what the parent was
B. Climate factor - very important
•temp and moisture the big keys
•rule of thumb:
•high temp, high moisture, high weathering
•example - soils deepest in warm, humid climates
shallowest in cold, dry regions
climate the SINGLE most important factor in soil generation on broad scale
C. topography
•slope and drainage important
•if slopes steep, soil easily eroded away, not much time for soil to mature
•Fig 12-3
D. Biological factor in soil development
•from total volume perspective, organic material very small fraction
•soil about 50% mineral and 50% air/water
•but organic component extremely important - gives the soil LIFE
•plants and animals, both decaying and alive
•tunneling, burrowing, digesting all mixes soil
•bacteria v. important…causes decomposition and decay
E. Time factor
•time required often dependent on other factors at work and the environment
•example - warm moist climate vs cool dry one - may take much less time
for soil to develop in former environment
•rule of thumb:
•soil forms quickly from sediments but very slowly from hard
bedrock
•to humans, soil still takes very long time to form (appears to us as a nonrenewable resource, like petroleum or groundwater)
III. Soil components
4 primary constituent groups: inorganic, organic, air, water
•Inorganic:
•sand, silt, clay, dissolved mins
•clay very important because of platy nature and negative overall charge
-can host lots chem rxns, hold lots of positively charged cations that
are often plant nutrients
•Organic matter
•less than 5% of volume, but very important
•variety of states:
•living
•dead: not decomposed/intermediate/decomposed
•many organisms small and large contribute to soil health
•aerate
•produce waste that becomes nutrients
•help with decomposition
•contribute N for plants
•Soil air
•important because half of soil is pore space
•soil air diff than that in open atmosphere
•more moisture
•more CO2
•less O2 (plant respiration from roots causes O2 consumption)
•Soil water
•from precip and grdwater
•very important - leaches nutrients from one place, deposits them in
another
•eluviation process too Fig 12-11
IV. Soil Properties
A. Color
•conspicuous but not definitive
•175 colors!
•Black/brown indicates organics
•red/yellow indicates iron oxide
•grey/blue indicates poor drainage, lots H2O
B. Texture
•Table 12-1 shows the grain sizes
•Texture triangle in Fig 12-15
•loam is center point, a mix of all 3 end-members
C. Soil structure
•clumps called “peds”
•too much sand and peds don’t develop - not enough cohesion
V. Soil chemistry
•nutrient availability is key for plant growth, and soil chem dictates this process
•colloids - very tiny - several types
•inorganic (crystalline platelets)
•organic (humus particles)
•together as suspension in water, they soak up much water, hold
ions
•cation exchange - (+)-charged cations such as Ca, K, Mg are all
important for plant nutrition
•negatively charged colloids attract these cations, hold them
•balance important - charge not too strong, not too weak
•some cations bond tightly, kick others out - this is “cation
exchange”
•CEC measures ability of soil to exchange - the higher the CEC,
more fertile the soil
•high CEC usu assoc with both high clay and high organic
content
•acidity & alkalinity - best soils are in the middle - not too extreme
VI. Soil profiles
developed by both depth and time through 4 processes:
•adding (energy, water, etc)
•losing
•moving (translocating)
•changing (transforming)
•the 5 factors from earlier influence these 4 processes
•soil horizons develop fig 12-20
•O horizon
•litter usu only in forest, not grassland
•A horizon
•“topsoil” - lots organics, seed germination here too
•E horizon
•lighter than A, due to leaching of organics, clay, ions by water
•B horizon
•“subsoil”, where materials leached from above are deposited
•C horizon - regolith - weathered bedrock, no organics
•R horizon - bedrock, unweathered
Note that WATER is ESSENTIAL to soil profile development - no water, no
profile
also note that horizons may be missing, and that varying levels of
maturity/immaturity exist in soils
VII. Pedogenic Regimes
5 major regimes that have certain physical/chem/biological processes
1. Laterization creates latosol (brick-red soil)
•from moist warm regions
•tropics and subtropics
•mins, nutrients leached quickly
•soils deep
2. Podzolization creates grey podzols
•moisture and leaching conds exist
•mid and high latitudes with conifers (acidic soils created)
•not much humus
•shallow soils
•low fertility
3. Gleization makes “gley” soils
•made in waterlogged, cool conditions
•slow decay, often around Great Lakes
•acidic and oxygen-poor
4. Calcification
•not much water
•leaching absent
•dry North American prairies
•Calcium carbonate is concentrated in hardpan layers
5. Salinization
•evaporating water leaves salts behind
•salts can be toxic
Fig 12-22 shows how soils develop in terms of temp-precip conditions
soil mapping technique - identify the most prevalent soil in an area
Compare climates to soils