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Biol 312 - terrestrial ecology > lecture 9 > Flashcards

lecture 9 Flashcards

1
Q

how does soil impact organisms

A
  • Important for why you see organisms where you see them
    Abiotic components are often not explicitly included in studies
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2
Q

how can u describe the study of ecology

A

The study of ecology can be described as the observation of patterns and processes

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3
Q

how does biota impact soil development

A
  • Vegetation - soil stability, biological weathering
    • Source of organic matter
    • Modifies microclimate- due to vegetation
      ○ Climactic factors changed under and around the plants - ex. Reduced exposure of the surface to wind
      ○ Slowing wind
      ○ Shading
      ○ Retaining snow
    • Decomposition and movement of material
    • Ex. Earth worms move the soil throughout the layers and transport things + physically break down organic matter
      The reason you see a conc. Pattern when looking at soil horizons is bc light hits above ground most = more PP = more organic matter
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4
Q

how does time influence soil development

A
  • Time over which soils develop influences their properties (will depend on PM)
    • Many soil forming processes occur slowly
      ○ Glacial retreat (till)
      ○ Wind deposited sediment (eolian)
    • Some occur quickly -
      *
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5
Q

what happens to phosphorus in soil over time?

A
  • Over time, secondary and organic phosphorus are found in larger quantities - chemical reaction with the soil
    Part of the natural cycle
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6
Q

How can human activity influence soil development

A
  • Extending agricultural footprint
    • Replacing communities that evolved under natural conditions with ones that are not adapted - crops fail, loss of vegetation cover, exposure of soil
      ○ Increasing dust after great depression
    • Nitrogen fixation decreased
      ○ Historical fixation due to plants - lost when they are replaced
    • Certain environments are not great for supporting primary productivity
      Ie. California is too dry, but introducing water can lead to issues such as salt accumulation in soil
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7
Q

direct impacts of humans on soil development

A

○ Nutrient inputs
○ Irrigation
○ Alteration of microenvironment
○ Increased erosional loss

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8
Q

indirect impacts of humans on soil development

A
  • Indirect:
    ○ Changes in atmospheric composition (deposition, climate)
    ○ Addition and deletion of species
    Acid rain caused by smelting activity = alters the ecosystem bc of change in PH - availability and chemistry of nutrients changed
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9
Q

what interactions take place in developing soil profiles

A
  • Development of soil profiles
    • Vast network of interactions taking place
    • Additions
    • Transformations
    • Transfers
      Losse
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10
Q

describe additions

A

precip (ions and soild particles)
organic matter
onto ground surface

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11
Q

describe transformations

A
  • Plant material and primary minerals
    • Addition of rainwater
    • Decomposition of OM; releasing CO2 and nutrients (N and P)
      physical, chemical weathering
      biological contributions
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12
Q

desribe physical weathering

A

○ Breakdown of parent material with no change in chemical composition
○ Expansion and contraction of rocks (freeze-thaw, heating-cooling, wet-dry cycles)
○ Roots growing into rock fissures
Roots will also push the rock as they establish

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13
Q

describe chemical weathering

A

○ Rocks react with acidic or oxidizing substances, usually in the presence of H2O
○ Primary broken down into secondary minerals
○ Stimulated by the Prescence of acids, water, and heat
Roots in rock fissures- - produce carbon dioxide + water = carbonic acid = far higher rate of acidification

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14
Q

describe biological contributions

A
  • Biological contributions
    ○ Decomposers, roots, lichen, etc
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15
Q

describe transfers

A
  • Usually down bc of gravity, but can be up
    • Usually result in losses
    • Vertical transfers- layering of soil
      ○ Downward: leaching and particulate transport in water
      ○ Upward movement and mixing:
      Capillary action (clay> sand), soil organisms
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16
Q

describe losses

A
  • Primarily solutions and gas; particles also lost via erosion
    • Amount lost due to leaching dependas on water and flow and solute conc.
      Gaseous losses depend on rate of gas production by microbes + diffusional paths through soil
17
Q

how do ecosystems differ in soil ? what is soil important for

A
  • Ecosystem differences in additions, transformations, transfers, and loss give rise to distinct soils and soil profiles
    • Soil is the 3rd most important factor in determining biota
    • Horizons may be thicker or even absent depending on the area
      *
18
Q

which horizon is LFH

A

O - ORGANIC MATTER DECOMPOSINF

19
Q

which horizons are mineral

A

A, E, B , C R
les than 30% OM by weight

20
Q

soil profiles in diff biomes ex

A
  • Dots are organic matter - distinct difference in the distrbution in the different systems
    • Bog/tundra: tremendous amount of organic matter at the top
      ○ Frozen ground for many months
    • Grasslands: greater gradient of distribution from the top down
      ○ Bc the amount of plants that are below ground can be up to 50% of the plant
      ○ Moderate precip and high variation
      Desert - low organic matter bc of lack of precip
21
Q

describe the LFH horizon

A
  • Forest floor
    ○ Litter: relatively fresh organic residues in which original structures are virtually intact
    ○ Fermented: dominated by partly decomposed organic materials, original structures are breaking down and discolored but still recognizable
    ○ Humus: organic residues in advanced stage of decomposition, original structures no longer discernable
    AH - upper mineral soil enriched in organic matter
22
Q

describe the A horizon

A
  • First layer where organic matter from LFH interacts with mineral soil
    • Zone of incorporation of OM into mineral soil
    • Generally rich in nutrients
    • High biological activity
    • Generally dark in color
    • Topsoil
    • Roots
      Important layer, when lost takes a long time to rebuild
23
Q

describe the E horizon

A
  • Zone of eluviation (leaching)
    • Soluble minerals and OM move out of this horizon
    • Generally a lighter “washed” appearance in color
    • Roots
24
Q

describe the B horizon

A
  • Zone of illuviation (deposition)
    • Accumulation of materials leached from above
    • Commonly clay, humus, and iron
    • Variable in color from reds and yellows to browns and greys
      Roots
25
Q

describe the C horizon

A
  • contains large fragments of unweathered parent material
    • Unconsolidated material that has been affected little by soil forming process
    • No roots
      R-bedrock
26
Q

describe The canadian system of soil classification

A
  • Rigorous classification system; based on soil horizon
    • Hierarchical: Order, great group, subgroup, family and series
    • 10 orders in the canadian system of soil classification
      ○ Differs slightly from american
      ○ Function of climate, vegetation, and plant material
      Latitudinal climate gradient
27
Q

describe Luvisolic soil

A
  • Forest soils
    • Loamy tills from underlying sedimentary rock or clayey lacustrine deposits
      Eluviation of clay from Ae to B horizon
28
Q

describe Chernozemic soil

A
  • Prairie, grassland
    • Hight root contribution to soil carbon
    • Thick A horizon
    • Dry conditions inhibit decomposition- buildup of humus in A horizon
      Dark Ah horizon
29
Q

describe organic soils

A
  • Very thick A horizon bc of conditions
    • Associated with peatlands: bogs, fens
    • Accumulation of water saturates soil - low O2 inhibits decomposition
      Build up of organic matter (peat)
30
Q

describe soil texture - what impacts it

A
  • Mineral part of soil consists of sand, slit and clay partical
    • Soil texture - relative properties of soil particles of different sizes
    • Fine textured, heavy (more clay, less sand)
    • Loamy (Mixture of the tree)
    • SA to volume ratio - bigger the sphere the more sa relative to volume
      Can do soil analysis where they partition each part out - tells you the key characteristics of the soil - good for agriculture + understanding soil composition

Biol 312 - terrestrial ecology (13 decks)

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