Chapter 5: Forest Soils Flashcards
1
Q
This is the upper, unconsolidated layer of earth surface
A
Soil
2
Q
What are the two main components of soil?
A
Organic and mineral parts
3
Q
What three things does soil provide to plants?
A
Support, water, nutrients
4
Q
What are five types of organisms that make up soil communities?
A
Bacteria, fungi, protists, invertebrates, and vertebrates
5
Q
Generally, what percent of soil is mineral?
A
45%
6
Q
Generally, what percent of soil is water?
A
25%
7
Q
Generally, what percent of soil is air?
A
25%
8
Q
Generally, what percent of soil is organic matter?
A
5%
9
Q
What is the term for soil creation?
A
Pedogenesis
10
Q
What are the five factors of soil formation?
A
Parent material, climate, biota, topography, time
11
Q
Parent material is the source of this soil component
A
Mineral component
12
Q
What are the two main sources of parent material?
A
Decomposed bedrock and transported material
13
Q
What three aspects of soil does parent material affect?
A
Fertility, soil depth, and development rate
14
Q
This type of soil formation is deposited by ice/glaciers
A
Morainal
15
Q
What 5 elements make up morainal soils?
A
Boulders, stones, sand, silt, clay
16
Q
This type of soil formation is deposited by flowing glacial meltwater
A
Fluvioglacial
17
Q
What two elements make up most of fluvioglacial soils?
A
Sand and gravel
18
Q
This type of soil formation is deposited by lake water
A
Lacustrine
19
Q
What two elements make up most of lacustrine soils?
A
Silt and clay
20
Q
This type of soil formation is deposited by stream water
A
Alluvial
21
Q
What three elements make up most of alluvial soils?
A
Sand, silt, clay
22
Q
This type of soil formation is deposited by wind
A
Eolian
23
Q
What two elements make up most of eolian soils?
A
Very fine sand and silt
24
Q
This type of soil formation is deposited by gravity
A
Colluvial
25
What three elements make up most of colluvial soils?
Sand, silt, bedrock fragments
26
What are five influences of climate on soil?
Weathering parent material; Erosion/transport of soil; Decomposition rates; Soil organic matter inputs; Decomposer biota
27
This is the breakdown of parent material; the first step in soil formation
Weathering
28
What are three ways soil biota affect soil formation?
Source of organic component; Organisms affect SOM accumulation; Organisms decompose and mix SOM
29
This topographical feature modifies other factors in soil formation
Relief
30
Are soils deeper and wetter on ridges?
No
31
Are soils deeper and wetter in depressions?
Yes
32
These topographical features restrict drainage
Shallow water tables
33
Which slope aspect is wetter, northern or southern?
Northern
34
Which slope aspect has lower organic matter, northern or southern?
Southern
35
What are two effects of topographic relief on soils?
Erosion and transport
36
Do soils take a short time to develop?
No
37
Do physical and biological properties of soils change with age?
Yes
38
Soils develop this as they age
Layered structure
39
What are soil layers called?
Horizons
40
What are the four horizon-forming processes?
Additions, losses, translocations, transformations
41
What are five examples of soil additions?
Sediments, SOM, water, air, solar energy
42
What are three examples of soil losses?
Evapotranspiration, erosion, leaching
43
What are three examples of soil translocations?
SOM movement, particle movement, movement of nutrients between layers
44
What are two examples of soil transformations?
Chemical changes and physical changes within layers
45
On what basis do soil scientists classify different soils?
Horizons
46
What soil horizons do capital letters identify?
Master horizons
47
What do lowercase and numeric suffixes denote in soil horizons?
Additional traits
48
This soil horizon is made up of surface litter, an organic layer of decaying plant and animal tissue
O horizon
49
This soil horizon is the mineral horizon below O, and is made up of humified SOM mixed with mineral material
A horizon
50
What is the A horizon also known as?
Topsoil
51
This soil horizon is the zone of leaching, and is made up of leached minerals and organic matter
E horizon
52
What is the E horizon also known as?
Eluvial zone
53
In what type of soils is an E horizon found?
Older, developed soils
54
This soil horizon is a zone of clays and minerals leached from above
B horizon
55
What is the B horizon also known as?
Subsoil
56
This soil horizon is made up of unweathered parent material (decomposed bedrock or transported material), and has little soil formation
C horizon
57
What is the C horizon also known as?
Substratum
58
What is the C horizon/substratum the source of?
Geological components of soil
59
This horizon is hard bedrock
R horizon
60
What are three soil color forming factors?
Mineral content, SOM, drainage/soil moisture
61
What does brown soil indicate?
High SOM
62
What does red soil indicate?
Well drained, high iron
63
What does grey soil indicate?
Poorly drained
64
This is used to classify color
Munsell color chart
65
This describes the mix of soil mineral particles
Soil texture
66
What are the three classes of particles that make up soil texture?
Clay, silt, sand
67
This soil particle is between 0.000 and 0.002 mm
Clay
68
This type of soil particle is between 0.002 and 0.050 mm
Silt
69
This type of soil particle is between 0.050 and 2.000 mm
Sand
70
This describes the physical arrangement of soil particles
Soil structure
71
What two things does soil structure affect?
Drainage and fertility
72
From what five factors does soil structure arise?
Chemistry; SOM; Organisms; Wetting/drying; Freezing/thawing
73
What are four characteristics of sandy soils?
Larger pores, low total porosity, dry, infertile
74
What are four characteristics of silt and clay soils?
Smaller pores, higher total porosity, wetter, more fertile
75
What soil type is the optimal mix of the three soil particles?
Loamy soils
76
Loamy soils have the best mix of these two soil characteristics
Porosity and fertility
77
What are five shapes produced by soil structure?
Granules, blocks, prisms, columns, plates
78
What are four functions of organic matter in soils?
Creates soil structure; Improves aeration/drainage; Source of soil nutrients; Energy source for soil food web
79
Most SOM comes from this
Litter
80
Litter is broken down into these two molecules
CO2 and H2O
81
The breakdown of litter releases these two things into the soil
Energy and nutrients
82
Tree litter is high in these two substances
Cellulose and lignin
83
How do cellulose and lignin affect the decomposition rate of tree litter?
Both slow decomposition rate
84
Litter decomposition creates this
Humus
85
What is humus?
The dark, amorphous end product of decomposition
86
For how long can humus persist?
Millenia
87
What are two reasons why humus is essential to soils?
Acts as a cement for soil structure; Source of soil nutrients
88
Soil acts as a reservoir for this
Water
89
What are the 7 roles of soil water?
Plant resource; Transport; Soil consistency; Aeration; Soil temperature; Soil biota; Erosion/deposition
90
What are five factors that influence soil moisture?
Climate; Vegetation; Soil permeability; Soil storage capacity; Topography
91
What are three factors that determine soil water holding capacity?
Soil texture; Soil structure; Organisms
92
How does soil texture affect soil water holding capacity?
Texture affects porosity
93
What is soil porosity?
Gaps of air between grains in a soil
94
Is the porosity of clay soils greater than sandy soils?
Yes
95
How does soil structure affect soil water holding capacity?
Soil particles aggregate, creating large pores/seams
96
What are two ways organisms affect soil water holding capacity?
Burrowing animals create tunnels; Tree roots create channels
97
What are the three fractions of soil water?
Gravitational water; Capillary water; Hygroscopic water
98
This type of soil water is held in cavities/large pores after rain, and is drained by gravity
Gravitational water
99
This type of soil water is held in small pores against gravity
Capillary water
100
What is capillary water also known as?
Available water
101
This type of soil water adheres strongly to soil particles and is unavailable to plants
Hygroscopic water
102
What are the three quantities of soil water storage?
Saturation point; Field capacity; Permanent wilting point
103
This soil water storage point happens when all pores and cavities are filled with water
Saturation point
104
What is the equation for the saturation point?
SP = Gw + Cw + Hw
105
This soil water storage point is the remainder after large pores drain
Field capacity
106
What is the equation for field capacity?
FC = SP - Gw
107
This soil water storage point is the fraction after available water is exhausted and leads to plant wilt
Permanent wilting point
108
What is the equation for the permanent wilting point?
PWP = FC - Cw
109
What type of soil has the highest available water?
Loamy soils
110
In what two U.S. areas is soil moisture highest?
Mississippi Valley and Great Plains
111
These soil organisms are over 20mm long and include moles, rabbits, and rodents
Megafauna
112
These soil organisms are 2-20mm long and include worms, beetles, centipedes, slugs, and ants
Macrofauna
113
These soil organisms are 100um-2mm and include mites and springtails
Mesofauna
114
These soil organisms are 1-100um and include bacteria, fungi, protists, and nematodes
Microfauna/flora
115
Soil biota are crucial for this process
SOM decomposition
116
These two types of soil organisms fragment, shred, and mix SOM
Macrofauna and mesofauna
117
These soil organisms respire SOM for energy and mineralize nutrients
Microfauna/flora
118
This process converts organic minerals to inorganic form
Mineralization
119
These microbes outnumber bacteria in forests and are more tolerant of low soil pH
Fungi
120
These fungi are root mutualists that aid in uptake of water and nutrients
Mycorrhizae
121
These fungi feed on dead organic matter
Saprophytic fungi
122
These microbes are also important decomposers, and are more abundant in grasslands than fungi
Bacteria
123
What are three roles that tree roots play in forest soils?
Source of SOM (from sloughing tissue during growth); Create channels that aid water movement and root growth; Grip and stabilize soils to reduce erosion losses
124
This is the zone around roots
Rhizosphere
125
What three microbes are found in high concentrations in the rhizosphere?
Bacteria, fungi, protists
126
What are three ways roots exert influence on soil chemistry?
Exuding sugars/proteins; Releasing H+ to solubilize nutrients; Releasing allelopathic chemicals
127
This is the acidity or alkalinity of soil solution
Soil pH
128
What are two things that soil pH affects?
Biology and nutrient availability
129
Do grassland soils have a lower pH than forest soils?
No
130
Why do trees release H+?
To free soil nutrients
131
Do conifer soils have a lower pH than broadleaf soils?
Yes
132
Do wet soils tend to be acidic?
Yes
133
What are five examples of cations that are key plant nutrients?
Ca2+, Mg+, Fe3+, K+, NH4+
134
What is the source of cations?
Breakdown of SOM and minerals
135
Cations are highly mobile in this part of soil
Soil water
136
Are cations not attracted to any soil particles?
No
137
This is a measure of soil fertility, the capacity of soil to retain cations
Cation exchange capacity
138
What are two factors that influence cation exchange capacity?
Surface area and surface charge
139
What surface area do sandy soils have?
Very low
140
What surface area do clay soils have?
Low to high
141
Can humus exceed high clays in surface area?
Yes
142
These two soil types have negative charge
Clays and humus
143
Do high CEC soils lose nutrients?
No
144
Does soil CEC decrease as the amount of clay rises?
No
145
Does soil CEC increase as the amount of humus rises?
Yes
146
Does soil CEC decrease as soil pH increases?
No
147
Cations are displaced from clay-humus by these
H+ ions
148
What is the order of cation attachment strength for five major cations?
H+>Ca2+>Mg2+>K+>Na+
149
This mixes with soil water to produce carbonic acid
CO2
150
These displace nutrients from soil particles
Acids
151
This describes how "full" the soil surface is
Base saturation
152
These six macronutrients are needed in large quantities by plants
N, P, K, Ca, Mg, S
153
These eleven micronutrients are needed in small quantities by plants
Fe, Mn, B, Cu, Mo, Zn, Cl, Co, Ni, Na, Si
154
Soil classification is based on these two factors
Formative factors and soil properties
155
What are the six levels of soil classification used by the USDA?
Order, suborder, great group, subgroup, family, series
156
What are three examples of soil orders named for their unique parent materials?
Andisols, Histosols, Vertisols
157
What are three examples of soil orders named for their unique environments?
Aridisols, Gelisols, Oxisols
158
What are three examples of soil orders named for their age of development?
Entisols, Inceptisols, Ultisols
159
What are three examples of soil orders named for vegetative influence?
Alfisols, Mollisols, Spodosols
160
What are the four important forest soil orders?
Oxisols, Ultisols, Alfisols, Spodosols
161
These soils are old, leached, and infertile, with <35% base saturation
Ultisols
162
What are two types of forests where Ultisols are found?
Southeastern pine and pine/oak forests
163
These forest soils have relatively high fertility and >35% base saturation
Alfisols
164
What are two types of forests where Alfisols are found?
Oak-hickory forests and northern hardwood forests
165
These are sandy, acid forest soils found in cold, humid climates
Spodosols
166
What are three types of forests where Spodosols are found?
Northern hardwood forests, Great Lakes hardwood forests, and boreal forests
167
These are intensely weathered soils that are leached and nutrient poor
Oxisols
168
In what type of forests are Oxisols found?
Tropical forests
169
What are Ultisol E and B horizon characteristics?
Yellow E and red clayey B
170
What are Alfisol E and B horizon characteristics?
Grey E and brown clayey B
171
What are Spodosol E and B horizon characteristics?
Grey E and reddish brown B
172
Spodosol B horizons are often high in this
Humus
173
What are Oxisol soil horizon characteristics?
Red and highly oxidized
