Facts

1
THE DIRT ON FOREST SOILS (CHAPTER 5)

• Facts
• Trees require soil!
• Soils affect forest composition productivity
• Forests affect soil properties productivity

2
THE DIRT ON FOREST SOILS (CHAPTER 5)

• Our Topics
• 1. Soil forming factors
• 2. Soil properties
• 3. Forest soil influence on trees ( vice versa)
• 4. Soil taxonomy (classification)

3
SOIL FORMING FACTORS

• 1. Initial material (parent material)
• 2. Climate
• 3. Organisms
• 4. Topography

4
SOIL MORPHOLOGY (PROFILE)

• Soil Profile (see Figs. 5.1 - 5.3 in text)
• 2-D view of soil excavation
• Profile is partitioned into soil horizons
• O fresh decomposing organic matter
• A organic matter inorganic minerals (mixed by
  disturbance)
• E mineral horizon that has lost clay, iron
  aluminum
• B contains weathering products leached from O,
  A, and/or E horizons
• C little affected by soil-forming processes
• R hard bedrock

5
SOIL PHYSICAL PROPERTIES

• Soil Color
• Depends on
• 1. Mineral composition (e.g., iron oxides ? red)
• 2. Organic matter content (e.g., high ? black)
• 3. Water drainage (e.g., poor drainage ? blue
  green)

6
SOIL PHYSICAL PROPERTIES (continued)

• Soil Texture (see Fig. 5.4 in text)
• Determined by proportions of
• 1. Sand (2 mm - 0.05 mm diameter)
• 2. Silt (0.05 mm - 0.002 mm)
• 3. Clay (lt0.002 mm)

7
SOIL PHYSICAL PROPERTIES (continued)

• Soil Texture (see Fig. 5.4 in text) influences
  (e.g.)
• Soil structure
• Aeration
• Water retention drainage
• Nutrient supply
• Root penetrability seedling emergence

8
SOIL PHYSICAL PROPERTIES (continued)

• Soil texture influences forest species
  composition
• E.g., sandy soils tend to have trees with low
  moisture nutrient requirements (e.g., pines,
  hemlocks, some oaks)
• E.g., silt/clay enriched soils tend to have trees
  requiring abundant moisture nutrients (e.g.,
  Douglas-fir, black walnut, some oaks)

9
SOIL PHYSICAL PROPERTIES (continued)

• Soil Structure (see Fig. 5.5 in text)
• Determined by arrangement of particles into
  peds
• Peds classified by
• 1. Size
• 2. Shape
• 3. Degree of distinction

10
SOIL ORGANIC MATTER

• Originates from
• Litter (via decomposition)
• Fine roots (via death decomposition)
• Improves structure
• Increases porosity and aeration
• Dampens temperature fluctuations
• Energy source for microbes
• Increases moisture-holding capacity
• Source of plant nutrients

11
SOIL ORGANIC MATTER (continued)

• Forest operations affect soil organic matter!
• Examples
• Shelterwood harvest vs. clearcut harvest
• Remove entire stem vs. remove only merchantable
  portion of stem
• Leave organic debris vs. remove organic debris
  following pruning or thinning
• Prescribed burn vs. no burn

12
SOIL WATER

• Serves as nutrient solvent (for transport)
• Important for
• Consistency
• Aeration
• Temperature
• Microbial activity
• Concentrations of nutrients toxic substances
• Soil erosion
• Influences distribution composition of
  vegetation
• Rarely optimum

13
SOIL WATER (continued)

• Available Water
• Water that can be absorbed by plant roots
• Influenced by
• Precipitation
• Vegetative demand
• Soil properties, which affect, e.g.
• Runoff
• Soil storage and drainage

14
SOIL WATER (continued)

• Forest operations affect soil water!
• Ditching
• Mechanical destruction of hardpans
• Irrigation
• Vegetation
• Establish vegetation (plants remove soil water)
• Species choice (may either increase or decrease
  soil water)
• Thinning (increases soil water)
• Herbicides for weed control (increases soil water)

15
SOIL ORGANISMS

• Decompose organic matter (which makes nutrients
  available for plants)
• Incorporate organic matter into soil (which
  improves soil properties)

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16
SOIL ORGANISMS (continued)

• 1. Roots
• 2. Mycorrhizae
• 3. Fungi
• 4. Bacteria
• 5. Protozoa
• 6. Algae
• 7. Animals (e.g., earthworms, insects)

17
SOIL CHEMICAL PROPERTIES

• Soil pH
• Definition
• pH ? negative logarithm of hydrogen ion
  concentration
• Numerical scale 1-14
• Acidic if lt7 (common in forest soils)
• Basic (alkaline) if gt7
• Exactly 7 neutral
• Soil pH important for
• Health of microbial populations
• Nutrient availability for plants

18
SOIL CHEMICAL PROPERTIES (continued)

• Cation Exchange Capacity (CEC)
• Cations ? positively charged ions (e.g., Ca2)
  many are forms of plant nutrients
• CEC ? soil ability to adsorb and release cations
• CEC depends on
• Soil organic matter (mostly negatively charged
  increases CEC)
• Amount and type of clay (e.g., CEC low in sandy
  soils)
• Soil pH

19
SOIL NUTRIENT DEFICIENCIES

• Nutrient deficiencies detected by
• 1. Visual plant (tree) symptoms
• 2. Soil analysis
• 3. Plant tissue analysis
• Beware of visual symptoms!
• Nutrient deficiency symptoms may mimic those of
  disease, insect, or moisture deficiency
• Soil or plant tissue analyses necessary for
  definitive diagnosis

20
FOREST FERTILIZATION

• Reduces nutrient deficiencies
• Increases
• Insect disease resistance
• Aesthetic appearance
• Costs
• Fiber yield (and so net profit)
• Environmental pollution
• Usually uses non-renewable resources
• Changes soil properties
• Municipal industrial wastes can be used
  (reduces environmental pollution)

21
SOIL SURVEYShttp//soils.usda.gov/survey/how_to/

• Soil survey reports contain
• 1. Soil maps
• 2. Soil descriptions
• 3. Soil use and management
• 4. Soil formation and classification
• 5. Laboratory data
• 6. Other general information

22
SOIL SURVEYS (continued)

• Soil survey reports used for, e.g.
• 1. Matching planted tree species to soil type
• 2. Evaluating impacts of proposed uses
• 3. Predicting water yield and quality
• 4. Planning recreational facilities
• 5. Road location design
• 6. Matching harvest methods to soil conditions

23
SOIL TAXONOMY (CLASSIFICATION)

• Seven Hierarchical Levels of Soil Classification
  (in U.S.)
• 1. Order (e.g., Ultisols, Alfisols, Spodosols)
• 2. Suborder
• 3. Great group
• 4. Subgroup
• 5. Family
• 6. Series
• 7. Type (most specific category)

24
INFLUENCE OF FOREST OPERATIONS ON SOIL QUALITY

• Example 1 Nitrogen Balance(will be
  shown/discussed in class)

25
INFLUENCE OF FOREST OPERATIONS ON SOIL QUALITY

• Example 2 Soil Erosion
• Erosion can be caused by, e.g.
• Recreation
• Road building
• Timber harvesting
• Site preparation (creation of favorable
  conditions for tree planting initial growth)
• Prescribed burns
• Chemical treatments
• Mechanical treatments
• Combinations of the above