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ERS 234 Final > Lecture 5 - Forest Soils > Flashcards

Lecture 5 - Forest Soils Flashcards

(47 cards)

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1
Q

What are forest soils? What do they provide?

A

It is a medium for plant growth. They provide:

  • mechanical support
  • moisture
  • nutrients
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2
Q

Why are forest soils not equivalent to agricultural or other soils?

A

B/c it has a forest floor with O horizon, split into LFH

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3
Q

What are soil forming factors that govern the properties of the natural soil material?

A
  1. Climate - productivity
  2. Topography - slope
  3. Biology - biomass quantity
  4. Geology - bedrock/mineral affecting pH
  5. Time
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4
Q

Why is soil vital to forest ecosystems?

A

B/c there is addition, transformation, translocation, and loss of materials during biogeochemical cycling

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5
Q

What is a soil profile?

A

It is a 2D vertical section/lateral view of a soil excavation and is divided to horizons (separate layers). The depths of each layer will depend on location

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6
Q

What is the O horizon?

A

It is the organic horizon that is divided into litter (leaves, branches, etc.), fungal matter (decomposed but still recognizable, and humus (decomposed and unrecognizable) - aka LFH layers

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7
Q

What is the A horizon?

A

It is a top soil horizon that is rich in humus and minerals. It’s unique b/c its a mix of OM and minerals

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8
Q

What is the B horizon?

A

It is a sub soil horizon that is poor in humus, rich in minerals, is lighter in colour, and has small rocks in it

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9
Q

What is the C horizon?

A

It is weathered rock fragments that have little or no plant life, and it gives a good idea of what the bedrock is made of

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10
Q

What is the D/R horizon?

A

It is the bedrock/parent material horizon

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11
Q

What is elluviation?

A

It is a leached soil horizon

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12
Q

What is illuviation?

A

It receives the leached materials

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13
Q

Go look at the slides for temperate vs. boreal soils

A

OKAY, I WILL!

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14
Q

What is a Munsell soil chart?

A

It is a chat used to give a name and code to soil. Colour can explain aspects like mineral composition (ex. red soil has high iron), OM content (ex. black soil has high OM), and drainage (ex. green/blue soil has poor aeration)

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15
Q

What is soil texture?

A

It is the proportion of sand, silt and clay and is based on particle size.

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16
Q

What are the different sizes of each soil separate?

A
  • gravel: >2mm
  • sand: 0.05-2mm
  • silt: 0.002-0.05mm
  • clay: <0.002mm
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17
Q

How is soil texture determined?

A
  1. place soil, water, and chemicals in cylindrical jar and let it sit to separate
  2. figure out the percentage of each separate with jar diameter and layer height
  3. follow textural triangle with each percentage to define soil type
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18
Q

What is soil structure?

A

It is the arrangement of soil particles based on particle size, shape and texture. OM, microorganisms, chemical reactions and wetting/drying all contribute to structure.

ex. granular structure has easy water infiltration compared to platy - granular and blocky usually found in forest soils

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19
Q

What are the important functions of soil organic matter (SOM)?

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A
  • provides structure by binding/gluing particles
  • increases aeration and porosity
  • moderates temperature fluctuations
  • increases moisture holding capacity
  • important source of nutrients and carbon (sequestration a slow process)
20
Q

Where does SOM come from?

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A

The majority is from litterfall because leaves decompose and release CO2, H2O and energy. Not all of it will decompose though (as microbes can’t break everything down), creating humus as a byproduct

21
Q

If SOM is found in undisturbed forests, it is:

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A

an equilibrium aka a carbon sink!

If there is a disturbance, some SOM is lost, making it a carbon source. Forests can be managed to minimize SOM loss by, for example, leaving behind slash

22
Q

What does soil moisture influence in forests?

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A

It influences distribution and growth of forest vegetation through temperature, aeration, microbial activity, runoff, erosion, and toxin accumulation

ex. too much water (flooding) kills trees

23
Q

How is water scarcity controlled?

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A

By eliminating competing vegetation to maximize water availability for desired trees

24
Q

How does soil retain water?

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A

Through adhesive forces. Strong adhesion prevents plants from taking water, so trees will shed some leaves to cope

25
How does water naturally move in relation to saturation?
It moves from saturated to unsaturated areas. Saturated flow occurs with high H2O availability and vice versa
26
What is the important role of soil organisms?
Important for tree growth and forest soil. They also decompose OM, release nutrients taken up by trees, influence soil profile development and form symbiotic relationships with tree roots (mycorrhizae)
27
How do soil organisms influence soil profile development?
They translocate nutrients from upper to lower horizons and are key in the development of the O horizon
28
How do roots impact the soil?
- they add OM with fine root turnover - stimulate microorganisms - produce organic acids that solubilize compounds - hold and exchange nutrients - produce toxic compounds to inhibit establishment/growth of other plants - protect against erosion
29
How does soil pH impact the soil?
- influence microbes - influences nutrient availability (N, P, Ca, Mg, etc.) - influences nitrification rate (ammonium to nitrate) Forest soils are typically acidic in conifer forests while temperate are closer to neutral.
30
What are cation exchanges in soil? How does it impact soil?
There are complex chemical reactions, cation exchange capacity (CEC), that occurs between soil particles (negative charge), plant roots and nutrients. It occurs when pH is >5.2 and different cations have varying degrees of attraction/exchange ability - rate determines soil fertility
31
What are soil macronutrients?
They are required in large quantities and are derived from minerals and OM in soil - N (only derived from OM) - P - K - S - Ca - Mg SCaMg KPN
32
What are soil micronutrients?
They are required in small quantities and are derived from minerals and OM in soil - Fe - Mn - B - Cu - Mb - Zn - Cl ClMb FeMnZn CuB
33
What do nutrients cycle through?
- atmosphere - vegetation - soil - bedrock - water - species - etc.
34
What is nutrient stock/abundance?
It is the amt of nutrients available in kg/ha
35
What is the major source of nutrient input (except for N)?
Weathering of minerals - the amt contributed depends on nutrient content of weathering rock. Young soils weather more than old soils ex. fast weathering occurs here b/c of the humidity and cold climate, but it would be slow in a desert because there is only wind to weather it
36
How is weathering measured?
Through stream gauging as it directly measures what is leaving the watershed. The disadvantages of this method is that nutrients in H2O can leach below the roots zone (porous bedrock) and that cannot be accounted for
37
How is photosynthesis a source of nutrient input?
It inputs CO2 into the system
38
How is litterfall a source of nutrient input?
Aboveground: the leaves, branches, fruiting bodies Below ground: fine root turnover Litterfall increases moving from the poles to the equator
39
How is stemflow & throughfall a source of nutrient input?
Nutrients in the precipitation passes through the canopy and the concentration may increase or decrease as it falls through the canopy. Decreases: from absorption by the foliage Increases: from leached nutrients on leaves and trunk (more common)
40
What is dry deposition? How is it a source of nutrient input?
It is a source of atmospheric input and is the absorption of dust/gases on canopy surfaces and by the soil. Nutrients/gases present on leaf surfaces are solubilized and become part of the throughfall. It is very difficult to quantify, provides specific instrumentation, and is not overly accurate
41
Why would one do an evaluation of site characteristics?
To help predict productivity! Analyzes: - slope - texture - drainage - temperature - soil depth
42
Why would one do an evaluation of tree height and dbh?
to develop models that predict site productivity
43
How is nutrient deficiency diagnosed?
- Visual symptoms like: unusual leaf structure, branch deformation, stunted growth - Soil analysis like: available nutrient content - Plant-tissue analysis: nutrient content in leaves (tissue)
44
How are nutrient deficiencies corrected? Explain.
With fertilizers - there are different types for different deficiencies, but to use the benefits must outweigh the environmental and economic costs. Rate of fertilization depends on initial fertility, tree species, age, and fertilizer type
45
How many soil types are there in the Cdn classification system?
10 soils in which 4 are found in forests
46
What are characteristics of a healthy forest?
- complex structure - high diversity - has an equilibrium between inputs and outputs - resistant to change - productive (biotic resources, etc.)
47
What is forest sustainability defined as?
"the continued ability of an ecosystem to provide good and services" ex. difficult with timber harvest because it reduces the sites productivity

ERS 234 Final (9 decks)

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