Cover Page

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Cover Page
Module 10 The Effects of Topography and Parent
Materials on Soil at Mount Lemmon and Biosphere 2
Center
Adam Nix Eli Pristoop J.C. Sylvan
Yuko Chitani Mei Ying Lai Lily Liew Asma
Madad
SEE-U 2001 Biosphere 2 Center, AZ Professor Tim
Kittel, TA Erika Geiger
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Introduction Soils
Soil is one of the most important bases of
terrestrial ecology because it provides a variety
of requirements for plants and animal life. The
principal properties that soil provides for
plants are anchorage, moisture storage (in that
soil is like a sponge storing water), and a
supply of nutrients. Soil creates habitats for
animals by providing space for them to live and
by determining the local chemistry. One of
the many definitions of soil is The
unconsolidated mineral matter on the surface of
the earth that has been subjected to and
influenced by genetic and environmental factors
such as parent material, climate (including
moisture and temperature effects), macro-and
microorganisms, and topography, all acting over
time and producing a productsoilthat differs
from the material from which it was derived by
many physical, chemical, biological, and
morphological properties and characteristics.
(as quoted in J. P. Kimmins, 1997, Forest
Ecology a Foundation for Sustainable Management,
2nd edition, Prentice Hall Press.) Many
animals play important roles in the soil,
including insects (springtails, beetles, and
ants), mites, millipedes, nematodes, annelids,
mollusks, burrowing vertebrates, mycorrhizae,
bacteria, and plant roots. Desert soils are not
turned over very often, but ants and burrowing
mammals do most of the turnover that occurs.
Plant roots also do much of the initial breaking
of the parent material into smaller components.
Soil has been called the least renewable
resource in the ecosystem. Unlike biodiversity,
plant growth, water resources, and most other
components, soil takes decades to be replenished
if it is lost.
Steve Slaff talks with students about the soil
profile at the summit of Mt. Lemmon.
The three most important mechanical
properties of soil are texture, structure, and
porosity. Texture is the composition of the soil,
or simply, what the soil is made up of. Some
soils are made up of sand, silt, and clay.
Determining the texture of a soil is a process
that will be further explained in the
methods. The structure deals with the shape, size
and grade of particles. Soil structure refers to
how the individual sand, silt, and clay particles
are arranged into stable aggregates Porosity or
pore space of soils is calculated from the Bulk
Density (Db) and Real or Particle density (Dp).
Texture, structure and organic matter are all
important in determining the overall soil
porosity. Coarse textured sandy soils have larger
pores but much less pore space than finer
textured clay soils.Soil is the link between the
organic and inorganic world.
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There are five factors that determine how a soil
develops.

• Parent material
• Particle size- dune sand vs. clay alluvium
• Chemistry, soluble limestone vs. decomposing
  granite vs. resistant basalt
• Regional Climate
• Temperature- cold favors humus accumulation
  organic material is added faster than it
  decays heat allows humus to decompose rapidly.
  
• Water flux- mineral leaching by high rainfall vs.
  Caliche formation under low rainfall.
• Organisms
• Organic matter input- acidic pine needles vs.
  grass roots.
• Vegetation cover determines rate of organic
  input and rate of surface erosion.
• Bioturbation due to prairie dogs, earthworms,
  termites, etc.
• Topography
• Water flow
• Whether a soil will be eroded, stable, or covered
  by more deposits.
• Solar radiation loading, which affects soil
  temperature and evaporation rate.
• Time
• Soil genesis It takes time for soil to develop
• Surface stability
• Climate changes-the longer the time, the more
  likely that climate will change.
• Human disturbancegrazing, land use, and fire.

Steve Slaff describes the parent materials in the
Santa Catalina Range.
Both physical and chemical weathering are
needed for soils to form. Weathering is the
process of physical and chemical changes in
rocks, which are caused by atmospheric agents
such as water, oxygen, and carbon dioxide.
Weathering takes place at the earths surface.
Weathering may involve the disintegration of
rocks into smaller particles, or the
decomposition of rocks into different minerals.
Long-term weathering often forms various kinds of
clays. In this lab we examined soils
from two different sites, analyzed, and compared
them. What differences or similarities do soils
from different topographical areas have? What
differences could topographical factors have that
influence the kind of soil and soil production?
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Horizon Definitions
L, F, H O LAYERS
The second component of soil structure is
referred to in terms of soil horizons. The
materials arriving at the surface layer, such as
leaf litter and other dead organic matter, are
processed within each horizon and then pass
through to the layer beneath it. The horizons are
abbreviated to single letters, and unfortunately
the nomenclatural systems differ between
continents. The top layer is the litter layer
(L), composed of litter that is slowly
decomposing and has been only recently deposited,
but is rapidly being broken down by biotic
activity. The next layer is the F layer, a
rapidly decomposing layer of litter leading to an
accumulation of a layer of raw humus (horizons
H and O - horizon O has material that is more
decomposed than horizon H) below it. The H layer
has litter that has been broken down to particles
and is usually very nutrient rich. Below the
humus layer, are the alluviated layers (A
horizons), layers that are very poor in metallic
elements like iron and aluminum, elements which
have been leached out (alluviated) of the forest
floor to the B horizons below. The alluviated B
horizons are layers that are rich in deposited
iron, aluminum, and other minerals (alluviated)
that were leached out of the A horizons. Below
the B horizons lies material that are not
considered soilthe C horizon consisting of
unweathered parent material or compacted rock
materials. The C horizon begins the bedrock
layers, where biological activity is almost
non-existent.
A LAYER
B LAYER
C LAYER
? The soil profile at the Mt. Lemmon site notice
the four distinct layers (or horizons) in the
bank.
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Map of Two Sites
Mt. Lemmon
Biosphere 2 Center
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Map of Regional Soil Profiles
MH2- Haplustolls- shallow, moderately slowly to
slowly permeable soils that formed in eolian
material over residuum derived from
basalt. TS6-Torrertic Haplustolls (New
classification Torrertic Hoplustolls) clayey
texture and deep wide cracks that are open more
than 6 months in most years formed in clayey
sediments, soft shales, or basic rocks, in
association with Aridisols and with aridic
subgroups of Ustolls. TS7-The Caralampi series
consists of very deep, well drained soils formed
in fan and slope alluvium from granitic and
volcanic rock. -very gravelly sandy loam -
rangeland. TS10-The Cellar series consists of
shallow and very shallow, somewhat excessively
drained soils formed in slope alluvium from
granitic rock.- very gravelly sandy loam
rangeland. FH5-Mirabal Baldy- Mt. Lemmon site.
Loamy sand. Bolsa quartzite.
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Climate Diagram of Mt. Lemmon Area
Courtesy of the Desert Research Institute
website http//www.wrcc.dri.edu
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Methods
Using screen sieves, we separated each
horizon of the soil profile into 5 different
particle sizes (5 mesh-gravel, 10 mesh-fine
gravel, 60 mesh-course sand, 230 mesh-fine
sand, bottom pan-silt and clay). Using a balance
scale, we weighed each of the particle types from
each of the horizons (Tables 12). We then used
Excel to determine the percent composition for
each horizon at each site. Another part of
testing the soils texture was with a flow chart
that helped determine the texture of the soil by
feel. We then tested each horizon from each site
on the plasticity and stickiness of the soil.
Using the Munsell soil color charts for both the
dry and wet soils, we identified soil colors
according to a standard that is universally
acknowledged. We then smudged these colors on a
white piece of paper for better contrast
(Results).
In this lab we wanted two different soil
types, so we collected a soil survey from Mt.
Lemmon, from an elevation of 8,500 feet. To
collect proper sample we labeled each horizon of
soil, clearly distinguishing one horizon from
another. After labeling the horizons we measured
the depth of each horizon. In order to get the
purest sample of each horizon we dug a vertical
profile. This vertical profile allowed us to dig
at the side of the soil, which helped prevent
other horizons from contaminating the sample. We
then carefully bagged the soil from each horizon
and labeled them. This method of sampling was
also used on the soil profile at the Biosphere 2
Center campus. The second soil profile was
collected at 3,852 feet. After we took
these samples, we analyzed them at the dry lab.
We performed a series of tests, such as the sieve
screen test, plasticity tests, texture makeup
tests, the smudge test, and the Munsell soil
color test. The sieve screen test has five pans,
and 4 of the pans have screens filtering
particles from largest to smallest, and the last
pan collects what remains. The mesh sizes are 5,
10, 60, and 230. A mesh size is an indication of
the number of openings per linear inch. This
test allowed us to separate soils to examine
their texture on four different levels.
Excavating a soil profile at the Biosphere2 site.
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Geologic Formations Mt. Lemmon and Biosphere 2
Center

• Mount Lemmon Naco group metamorphosed
  Paleozoic sequence, mostly limestone, Bolsa
  quartzite
• Biosphere 2 Center Dissected Neogene basin fill,
  overline terrace and pediment gravel sheets and
  local alluvium

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O
O
A
A
B
B
C
C
R
Top Mt. Lemmon soil profile analysis, Mei and
Adam working on the texture tests. Bottom
Biosphere 2 soil profile analysis, Asma working
on the Munsell color and smudge Tests.
Top Mt. Lemmon profile (Letter denotes layer)
Bottom Biosphere 2 soil profile
Top Detail-view of Mt. Lemmon soil
profile Bottom Detail-view of Biosphere 2 soil
profile
A
B1
A
B2
B1
B2
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Pyramid of Soil Texture
Biosphere2
Mt. Lemmon
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Table 1 Mount Lemmon
Lat/Long 32.44 N / 110.78W, Elevation 2764
meters, 8500 feet Site Description Old growth,
near summit, cooler, breezier climate, more
rainfall, more organic materials
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Soil Composition Mount Lemmon
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Table 2 Biosphere 2 Center
Lat/Long 32.57 N / 110.84W , Elevation 1174
meters Site Description Arid, Desert, grasses,
small trees, succulents shrubs, less than 10" of
rain, alluvial deposition
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Soil Composition Biosphere 2 Center
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Results

• Based on the Texture Analysis and the Munsell
  Color Test, the soil profiles of Mt. Lemmon and
  Biosphere 2 are as follows
• Mount Lemmon
• O 3cm black/brown, charcoal, leaf litter
• A 0-26cm dark grayish brown, sandy loam
• B 26-46cm yellowish brown, sandy clay loam
• C -46-156cm brown weathered rock, loam
• Bedrock -156
• Biosphere 2
• A 0-30cm brown, sandy clay loam
• B1 030-50cm reddish brown, clay
• B2 -50-85cm yellowish red, sandy clay loam
• B3 -85 - yellowish red, sandy clay loam
•  
• The Screen Sieve Analysis was affected by
  imprecise methods (see conclusion)
• Mount Lemmon
• Gravel accounted for the largest percentage of
  mass from O to C layers.
• Coarse sand accounted for most of the non-gravel
  mass.
• With increasing depth, percentage of silt and
  clay decreased.
• Biosphere 2

Smudge Tests
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Discussion Parent Material, Topography Soil

• The unconsolidated mineral matter on the
  surface of the earth that has been subjected to
  and influenced by genetic and environmental
  factors such as parent material, climate
  (including moisture and temperature effects),
  macro-and microorganisms, and topography, all
  acting over time and producing a
  productsoilthat differs from the material from
  which it was derived by many physical, chemical,
  biological, and morphological properties and
  characteristics.
• To investigate this working definition for soil,
  we were asked to consider two questions
• What differences or similarities do soils from
  different topographical areas have? And what
  differences could topographical factors have that
  influence the kind of soil and soil production?
• To answer these we took soil from two distinct
  topographical localesone from a road cut near
  the top of Mt. Lemmon (elevation 8,500 ft.), the
  other from a road cut on the Biosphere 2 campus
  (elevation 3,852 ft.). We looked at soil
  texture, color, consistency, structure we also
  looked at the topography, climate, and the
  general characteristics of each site.
• Of the five functional factors that make soil
  (topography, parent material, time, organic
  forces, and climate) we found topography and
  parent material to have the most pronounced
  affect on the texture, structure, and the
  physical and chemical characteristics of our
  samples.
• Not that climate, biotic activity, and time are
  unimportant to soil development, but parent
  material and topography have shape how these
  other (crucial) factors function. The parent
  material at a given site influences the
  interaction between organic and inorganic
  materialse.g. quatz and limestone weather
  differently and so form very different soils.
  Topography is a deciding factor in the
  microclimate. Elevation effects temperature and
  moisture levels at a given site these in turn
  are limiting factors for the vegetation growing
  there and the kind of organic material that they
  into the soil.

Eli takes a closer look at the clay.
One note about time. Though it is a passive
agent in this process, it is perhaps the key
ingredient in the creation of soils. The process
of physical and chemical changes in rocks caused
by atmospheric agents such as water, oxygen, and
carbon dioxide takes place over millions of
years. Soil is a living process (a living
labyrinth, Tony Burgess calls it) and like most
living things it takes time to develop.
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Mount Lemmon
TOPOGRAPHY At 8,500 feet, the Mount Lemmon site
is a breezy mountaintop characterized by its cool
temperatures and old growth forest. Ponderosa
and Limber Pines, Douglas and White Firs all
tower 60 ft or more over the forest floor. In
the space between these trees, small stands of
Quaking Aspens and Rocky Mountain Maple saplings
grow. Part of the reason for high biotic
productivity in the area has to do with an
abundance of rainfall 788mm of precipitation per
year on average, according to the nearby
Palisades Ranger Station which has been compiling
yearly climate data for years (see above table).
These forests benefit from late summer monsoons,
as well as snowfall in late fall/early winter.
Referring to the local climate of the Santa
Catalina Mountains, the Arizona AgNIC reports,
On high peaks at 9000 to 10,000 feet, snow
persists all winter and accumulates to 20-40
inches. Summer rains fall June - September,
originate in the Gulf of Mexico, and are
convective thunderstorms. Winter moisture is
frontal, originates in the Pacific and Gulf of
California, and falls as rain or snow in
widespread storms of low intensity and long
duration. May and June are the driest months of
the year. Humidity is generally low. Temperatures
are mild in the summer to cold in the winter.
Freezing temperatures are common from October
through April. Frost free period ranges from 120
to 260 days.
We were surprised at first to discover less
biodiversity of plant and arthropod life at this
site, but given the colder temperature
regime--the minumum daily temperature in the
Santa Catalinas drop below freezing during four
months our of the yeara chill that many plants
thriving in the lower elevations around
Biosphere2 could not tolerate. Thus because of
its topography, the microclimate on Mount Lemmon
is much like that found in temperate forests at
higher latitudes. Vegetation contributes a
substantial amount of organic material to the
soil profile every year as reflected in the L, H,
and O layers of the soil profile. We estimated
this to be 3cm in our profile. It is worth noting
that we could expect more given the sheer amount
of organic activity at Mount Lemmon. The fact
that there was not a thicker O layer is strong
evidence of the effect of erosion on overall soil
formation at higher topographical points. The
deep roots of the trees, and the life forms that
they support, also help to break down the soil
structure through the process of biturbation.
These dense networks of roots and the burrows of
vertebrates and arthropods that live on the
forest floor provide conduits for water thus
aiding in the process of weathering of the rock
material. Another contributor to the character of
this O layer has been fire. Charcoal found in the
litter over the O layer suggests a history of
forest fires in the area. These fires allow for
a much more rapid decay of organic material and
nutrients than normal decomposition. Judging from
the vegetation, there has not been a fire in
recent years. Human disturbance even when it has
profound impact of a local ecology does not tend
to have any long term geological effects for
this reason it is considered more of a historical
phenomenon than a geological one. In an indirect
way, topography also influences human disturbance
and land use policy. Mount Lemmon is a popular
tourist site and is used primarily for recreation
purposes. Land use in the immediate area is
limited to these activities, though there is a
great deal of construction on roads in the area.
Currently these are the only significant
disturbances to the soil.
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Temperate forest near the top of Mount Lemmon.
PARENT MATERIAL According to Steve Slaff, the
rock material that forms the basis of our Mt.
Lemmon site is called Bolsa Quartzite. (He also
referred to it as Cat Mountain Rhyolite.) The
rock formations in this area were probably laid
in the Pleistocene period and influence the soil
type here, known as Mirbal Baldy. There is almost
no volcanic material in the Santa Catalina Range
of which Mt. Lemmon is a part. The parent
material is broken down over time in the C layer
of the soil. This fact plus the enormous amount
of organic material available to the process are
perhaps the two most distinguishing factors from
the Biosphere 2 site.
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Biosphere 2
Topography Compared with Mt. Lemmon, the
landscape of our second site is limited mostly by
availability of water. This biome would be best
classified as Apacherian mixed scrub savanna,
which, according to Dr. Tony Burgess, is
classified as coexisting growth forms that
include grasses, subshrubs, stem succulents and
shrubs (Burgess 1994). Long dry spells
punctuated by erratic and variable rainstorms
make for a very unstable plant community. This
area has a much larger percent composition of
grasses than the site on Mt. Lemmon. This makes
the whole community susceptible to frequent fire
and thus limits extensive long-term productivity.
The pattern of dry periods followed by heavy
rains means that summer storms cause erosion.
Plants have had to adapt their root structure to
these extreme conditionsgrasses have quick
growing shallow roots to take advantage of the
heavy summer rains, trees and some shrubs tend to
send deeper roots into the soil to take of water
that seeps deeper into the profile during winter
storms. Warm average temperatures protect
species vulnerable to frosttrees like the
mesquite, and succulents. Sandy soils work to
the advantage of these type of trees, since they
are more porous and allow for more water during
the characteristic heavy storms to penetrate
deeper into the soil profile. Another factor in
the topography of this site is extensive grazing.
While the ground directly above our sampling
site did not appear to have been grazed recently,
the Apacherian savanna has historically been
overgrazed. Overgrazing can erode the soil, by
trampling microorganisms that help knit the soil
structure together. They also significantly
reduced the amount of biotic material available
to the soil process. When cattle are introduced
to the ecosystem, much less biotic material and
nutrients are returned to the soil. Compared to
the Mt. Lemmon site, there is very little litter
at the Biosphere 2 Center. The topography is
marked islands of fertility under trees where
litter and hungry nutrient grasses tend to gather
leave top soil levels vulnerable to erosion.
This may have had something to do with why we
found no O layer at the Biosphere 2 site.
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• Parent material The geological basis of
  Biosphere 2 is called the Cordones Surface. It
  is part of an ancient alluvial fan deposited by
  runoff from the Catalina Mts. during basin and
  range faulting. The Cordones Surface formed from
  mixed alluvial deposits of different kinds of
  rocks including Paleozoic sedimentary rocks,
  metamorphic rocks, and Tertiary granites Since
  then, two processes have prevailed over time in
  the creation of this soil composition. Eluviation
  occurs when water percolating down through the
  soil leaches substances out of the upper layers.
  The acidic water dissolves most minerals, except
  quartz, and carries them deeper into the soil.
  Illuviation occurs as water percolating down
  through the soil carries materials from upper
  layers into deeper layers. An illuvial soil
  horizon has accumulated clays or minerals
  transferred by water flow from overlying soil.
  Over time these two processes can change a
  uniformly mixed alluvial deposit into a mature
  soil with distinctly different horizons
  (Burgess). This explains why we found clay
  interspersed many rounded rocks in the soil
  horizon.
• Clay comes some from weathering within the
  original deposit but most is brought in as
  windblown dust and raindrop nuclei. This dust
  often consists of oxidize iron-based material
  which give the soil a ruddy appearance. You can
  see this in the smudge tests the samples from B2
  are much redder than those on Mount Lemmon.
  Percolating water gradually moves clay particles
  down through the soil. In early stages this
  forms clay films on clods and pebbles. As clay
  continues to accumulate, water movement within
  the horizon is slowed hence clay is not moved
  into deeper layers, forming with is called an
  argillic horizon. On ancient alluvial fans, such
  as the Biosphere 2 campus, Holocene erosion has
  exposed the Pleistocene argillic and calcic
  horizons. These exposed layers become parent
  material for new soil formation. This process is
  typical of lower elevations in the Basin and
  Range Geologic Province. Over time the low level
  of precipitation (usually less than 12 inches per
  year) forms a horizon of caliche, a cement layer
  made from calcium carbonate (Burgess). This
  layer is almost nonexistent in areas of greater
  and more consistent precipitation (like the
  temperate forests of the Northeast), but we found
  that it was very prevalent on the B2C campus.
  The presence of caliche was one of the major
  differences between the soil profiles.
• McAuliffe in his essay on desert soils in the
  Natural History of the Sonoran Desert describes
  the slow process by which caliche horizons are
  formed They start as thin, patchy coats of
  whitish calcium carbonate on the lower surfaces
  of pebbles and small stones.These
  weakly-developed calcic horizons can form within
  a few thousand years. Accumulation of more
  calcium carbonate eventually produces thicker,
  continuous coatings on pebbles and stones or
  pronounced whitish nodules in fine-grained parent
  materials. Eventually, additional accumulation of
  calcium carbonate fills the soil interstices
  between pebbles or nodules and the calcic horizon
  becomes plugged, greatly restricting the downward
  movement of water. Once this occurs, calcium
  carbonate may continue to accumulate on the top
  of the calcic horizon in hard, cemented layers
  and may literally engulf and obscure overlying
  soil horizons in the process. It takes many tens
  to hundreds of thousands of years for such
  strongly-developed calcic horizons to form.
  Sometimes hard, whitish caliche becomes exposed
  on the surfaces of very old soils when erosion
  removes overlying, less erosion-resistant soil
  horizons. These partly eroded soils are very
  common throughout the Sonoran Desert and are
  called truncated soils.
• Thus the presence of a caliche layer not only
  tells us something about the content of the soil,
  it also serves as evidence of the climate that
  created it. The thick caliche layer we found in
  out Biosphere 2 sample would suggest that this
  area has experienced extreme aridity for quite
  some time. It can also give us a picture of the
  future topography and soil composition since
  caliche erodes unevenly to create exposed or
  slightly buried surfaces that shed water in
  weathering crevices, resulting in a landscape
  with patchy water infiltration and retention,
  and facilitating even more run-off, and more
  erosion, during heavy summer thunderstorms
  (Burgess). The geology of the landscape also
  exacerbates many of the environmental/climatic
  factors that shape this community and the soil
  profile, and creates a patchwork of different
  soil textures and characteristics. This is
  partly why desert soils are so hard to classify.

22
The Formation of Caliche in Arid Soils
From Phillips and Comus. 2000. Natural History of
the Sonoran Desert. Arizona Desert Museum Press.
Tucson.
23
Conclusion

• How did the soils differ? How does topography
  affect local climate? How did different parent
  materials result in different soils?
• In this exercise, we learned various
  techniques for sampling and examining soil
  profile. For example
• Sieve test
• Texture tests smudge test, ribbon (plasticity)
  test, stickiness test
• Munsell Color Test
• Topography affects climate, and together,
  these two factors significantly influence the
  soil composition. The higher elevation of Mount
  Lemmon results in more rainfall, and a more
  breezy climate. The lower elevation of Biosphere
  2 results in a dryer, hotter climate. Analysis
  of the soils indicated that the Mount Lemmon soil
  had more gravel and organic material in it than
  the Biosphere 2 soil, whereas the Biosphere 2
  soil had more coarse sand in it. This is because
  the Mount Lemmon site has a colder climate, where
  litter decomposes more slowly than in the arid
  climate at the Biosphere 2. The arid climate
  here results in less rainfall which, in turn,
  favors the formation of caliche found in the
  Biosphere 2 soil.
• Differences in the parent materials of the
  soils also influence soil composition. Bolsa
  quartzite was the parent material of the Mount
  Lemmon soil this material resulted in the
  softer, easily broken apart, weathered rock found
  in one of the soil layers. The parent material
  of the Biosphere 2 soil is alluvial deposits.
  Rust in the alluvial deposits results in the rust
  color of the soil at the Biosphere 2.
• In analyzing the soil samples collected, we
  learned that there are not many quantitative
  tests that can help us accurately describe the
  soil composition percentages. Most of the
  results that we obtained were from qualitative
  assessments, such as the Color Test and the
  Smudge Test. We found discrepancies that might
  have a lot to do with how we implemented these
  tests.
• In the future, we need to collect sufficient
  amount of soil so that we can replicate our test
  for more accurate results.

Soil profile Biosphere 2 ?
24
References Acknowledgements
http//www.columbia.edu/itc/cerc/seeu/bio2/index.h
tml http//homepages.which.net/7Efred.moor/soil/f
ormed/f0107.htm http//www.statlab.iastate.edu/soi
ls/osd/dat/C/CABEZON.html http//ialcworld.org/soi
ls/nonaridisols/nonaridisols.html http//www.statl
ab.iastate.edu/soils/osd/dat/C/CARALAMPI.html http
//www.statlab.iastate.edu/soils/osd/dat/C/CELLAR.
html http//interactive.usask.ca/skinteractive/mod
ules/agriculture/soils/soilphys/soilphys_depo.html
http//www.wrcc.dri.edu McAuliffe, Joseph R.
Desert Soils. A Natural History of the Sonoran
Desert. Eds Steven J. Phillips. Arizona-Sonora
Desert Museum Press Tucson, 2000 Burgess, T.
1995 Desert Grassland, Mixed Shrub Savanna,
Shrub Steppe, or Semidesert Scrub? Pp.31-67 in
The Dilemma of Coexisting Growth Forms.
University of Arizona Press, Tucson. Dickinson,
William R. 1992. Geologic Map OF Catalina Core
Complex And San Pedro Trough Arizona Geological
Survey contributed Map CM-92-C. 1125,000
Geological Society of America Special Paper
264. Macbeth, Gretag. MUNSELL SOIL COLOR
CHARTS year 2000 Revised washable Edition.
MUNSELL COLOR 617 Little Britain Road, New
Windsor, NY 12553. Steve Slaff Lecture on geology
and soil. 6/19/01, Mt. Lemmon, AZ.