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CXB Ecological Systems > Test 2.3 Deforestation, Afforestation, Mining and Agriculture > Flashcards

Test 2.3 Deforestation, Afforestation, Mining and Agriculture Flashcards

1
Q

Why is wood important In rivers?

A

Wooded debris: source of food

Structure for habitat

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2
Q

Meaning of CWD & LWD

A

Coarse wooded debris

Large wooded debris

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3
Q

Importance of CWD & LWD

A

LWD contributes to heterogeneity (diversity) of habitat: riffles, runs, pools

  • Traps gravel- especially important for fish spawning
  • Protects banks from debris
  • Provides habitat for macroinvertebrates
  • Stabilizes flows- evapotranspiration
  • Stabilises temperature regimes
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4
Q

Importance of riparian vegetation in terms of LWD

A

Provides cover and produces leaf litter CPOM - food for fish

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5
Q

What is ideal about salmonid spawning gravels?

A

• Ideal habitat: coarse gravel with little ‘matrix’ of fine sediments
- Allows flow of clean, well-aerated water for egg development
• Problem if excessive amounts of ‘fines’
- Especially <0.84mm
- Clogs gravels & reduces flow and DO

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6
Q

What is the effect on light due to timber harvesting on streams?

A

• Light levels & nutrients

  • Opening up canopy increases light
  • Nutrients leached from soils
  • Greater development of phytobenthos (algae)
  • Greater densities of invertebrates – food for juvenile salmon:
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7
Q

What is the effect on stream flows due to timber harvesting on streams?

A
  • Less evapotranspiration
  • Increased flood events
  • Lower base flows
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8
Q

What is the effect on temperature due to timber harvesting on streams?

A
  • Greater variability in temperature
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9
Q

What is the effect on fine sediment harvesting on streams?

A
  • Clogging of interstital spaces / under stones bad for some mayflies; caddisflies; stoneflies
  • May favour burrowing forms: some worms, fly larvae
  • Algae on stone surfaces reduced (smothered
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10
Q

Best management practices of streams:

A

• Leave a buffer strip of 30m either side of rivers
• Manage drainage patterns
- Prevent runoff of fine sediments
- Slash debris

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11
Q

Best management practices in mining operations

A
  • Use settling ponds- trap & remove sediments
  • Re-contour streams
  • Remove tailings
  • Replant with natural vegetation
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12
Q

Name forms of organic wastes

A
  • Manures: direct or sprayed onto fields
  • Slurry & washings from buildings
  • Milk and dairy washings
  • Silage liquors
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13
Q

What % of the world do forests cover?

A

30%

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14
Q

What % of the UK do forests cover?

A

13%

-2.3% ‘ancient’ but not post ice-age ‘old growth’ forest

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15
Q

Meaning of Obligate wood species

Meaning of Facultative wood species

A

Obligate: Only found on wood in streams- e.g. Chironomidae

Facultative: May be found on other substrates

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16
Q

How are old growth forest river streams important for fish (salmon) species?

A

LWD streams provide habitat for all stages of life cycle:

Deep pools

Refuges under logs for adults

Clean gravels trapped by woody debris for spawning

Rich food resource and cover for young fry fish

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17
Q

Why are salmonid spawning gravels an ideal habitat

A

Allows flow of clean, well-aerated water for egg development

Problems if excessive amounts of ‘fines’ (<0.84mm)
-Clogs gravels & reduces flow & DO

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18
Q

What is yarding and what are its ecological effects?

A

The dragging of logs to central area for transport generating disturbance to soils and creates sediment

Disturbance generates disturbance; fine trashy material when wood is sawn

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19
Q

Effects of timber harvest on stream channels path?

A

More simplified river channels: traded & complex to simple single channel system

e.g. Willamette River Oregon

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20
Q

Effects of timber harvest on stream light & nutrients?

A
  • Opening up canopy increases light
  • Nutrients leached from soils
  • Greater development of algae
  • Greater densities of invertebrates
  • Food for juvenile salmon

Old growth forest: lower algal growth
Clear cut forest: highest algal grow
Density of salmon fry strongly correlate with algal biomass

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21
Q

Effect of timber harvest on stream flows

A
  • Less evaporations-transpiration
  • More rapid runoff
  • Increased flood events
  • Lower base flows
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22
Q

Effects of timber harvest on temperature

A

-Greater variability in temperature due to reduced shading

  • Increased summer temperatures (heat/DO stress)
  • Greater algal production

-Extreme winter cold temperaturesger

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23
Q

How does amount of fine sediment affect permeability & oxygen?

A

As the amount of fine sediment (<0.88mm) amongst the gravel particles increases - the permeability (allowing oxygen flow) declines rapidly

24
Q

How does fine sediment affect invertebrates?

A

Clogging of interstitial spaces / under stones: bad for some mayflies, caddisflies, stoneflies

May favour burrowing forms. Some worms, fly larvae

Algae on stone surfaces reduced (smothered)- fewer grazers

25
Q

How does turbidity affect invertebrates?

A

Reduced light penetration

Algae on stone surfaces reduced&raquo_space; fewer grazers

26
Q

Meaning of ‘Slash’

A

Woody debris especially in small streams
-Decays & uses up oxygen
May change hydrology & ecology

27
Q

What is the most valuable part of the forest with respect to the stream?

A

The riparian zone 30m from the bank

40% of woody debris comes from first meters away from stream

28
Q

How can timber harvest be managed better? (Ecologically with fish communities in mind)

A

Leave 30m riparian zone untouched

Manage drainage patterns
- prevent runoff of fine sediments
-

29
Q

What is the relationship between Coho salmon and volume of large woody debris?

A

Positive relationship

More woody debris = better for salmon

30
Q

Describe fish productivity in old growth streams

A

Lots of CWD LWD provides refuge from fast flows. Good proportion of fish survive the fast flows through to the spring

31
Q

Describe fish productivity in Clear-cut streams

A

More light due to cut back trees, algal growth, greater density of invertebrates, increase in number of young fish.

No protection from winter flood flows, a lot wash out and die. Productivity less than old growth forest

32
Q

Describe fish productivity in buffered streams

A

Happy medium
Logs providing refuge: production in spring is higher

Light allowed to reach stream; increase in young fish
Strip of trees still provides woody debris providing refuge from high flows in winter so fry production in spring is higher

33
Q

Name afforestation common commercial species and their beneficial features

A 
Sitka spruce (UK)
Monterey Pine (NZ)
-Fast growing on nutrient-poor soils (28 years from planting to harvesting)
34
Q

Current UK woodland cover

A

12.9% most of which commercial forest

Minimum 5% between WW1 & 2
Big increase in planting post war- Forestry Act
Incentive to replace commercial woodland with native species

35
Q

Current NZ % of forest that is commercial

A

96% - major exporter

36
Q

Three stages of commercial forestry

A

Ground preparation
Closure of canopy
Felling

37
Q

What occurs in the Ground Preparation phase of commercial forestry and what are the impacts?

A

-ploughing, draining, road construction, planting

Impacts:

  • Increased sediment and turbidity- infilling of channels
  • Increased flows during periods of high rainfall
  • Leaching of nutrients (& herbicides) from soils
38
Q

What occurs in the Closure of Canopy phase of commercial forestry and what are the impacts?

A

Rapid, dense growth

Impacts:

  • Interception of wet and dry deposition; acidification
  • Exclusion of light
  • Reduced summer temps; raised winter temps
  • Reduced primary productivity
  • Reduced macro invertebrate abuncance
  • Study in Scotland showed 15% reduction in trout growth in afforested streams
39
Q

What occurs in the Felling/Logging phase of commercial forestry and what are the impacts?

A

Similar effects to removal of old-growth forests but not as marked

Impacts:

  • Altered flow regimes
  • Increased sedimentation
  • Acidification
  • Reduction in light penetration and productivity
40
Q

Best management practices for afforestation

A

30m riparian vegetation buffer strips

Good ditching and interception of runoff

Removal of ‘slash’ from small streams

Minimise use of pesticides & nutrient additions

41
Q

Effect of gold mining in Alaska on rivers

A

Before:
Natural braided river
Natural riparian zones

After:
Channel moved
Sediments excavated and gravels sorted - washed
Huge amounts of sediment generated

42
Q

Impacts of left tailings (abandoned gravel heaps) on rivers

A

Leach heavy metals: As, Al, Zn, Pb, Cu, Hg

  • Toxic effects
  • Example of ‘press’ disturbance
43
Q

Mining impacts

A 
Heavy metals
Chlorides
Ferric hydroxide
- smothers substrate
Impacts on algae, invertebrates, spawning
44
Q

Best management practices in maintaining rivers affected by mining operations

A

Using settling ponds- trap & remove sediment
Re-contour streams
Remove tailings
Replant with natural vegetation

45
Q

What are some common practices and characteristics of agricultural activities?

A
  • Removal of natural vegetation
  • Altered hydrology
  • Reduced inputs of natural organic material
  • Increased erosion ‘poaching’ - sediments e.g. potato turning
  • Livestock manures
  • Artificial fertilisers
46
Q

Name dominant forms of pollution in agricultural activities

A

Farm wastes
Nitrates
Pesticides
Sediments

47
Q

How do pollutants from farmlands reach rivers?

A

Wash in directly

Leach through soils

Manure spread on ground- wash into rivers

Animals may have direct access to rivers

48
Q

Name forms of organic wastes

A
  • Manures
  • Slurry & building washings
  • Milk & dairy
  • Silage liquors
49
Q

What pollutants have the lowest Biological Oxygen Demand (BOD) in order in mg l-1?

A

Clean river water <5mg l-1

Treated sewage ~20mg l-1

Untreated sewage ~300mgl-1

Dilute dairy parlour & year washings 1000-5000 mg l-1

Liquid effluents draining slurry stores 1000-12,000 mg l-1

Cattle slurry 10,000-20,000 mg l-1

Pig slurry 20,000-30,000 mg l-1

Silage effluents 30,000-80,000 mg l-1

Milk 80,000-120,000 mg l-1

50
Q

What are the % sources of N in rivers?

A

Agricultural land 60%
Sewage treatment works 35%
Other land 5%

51
Q

What are the % losses of N in crops?

A

Potatoes 100%
OSR 70%
Peas 70%
Beans 60%

52
Q

Impacts of nutrients (increased N & K)

A

Eutrophication

  • Rapid plant growth
  • Death & decay
  • Microbes use up O2

^Increases turbidity: even more reduced light

53
Q

How does increasing nutrients effect the vegetation in a stream?

A

With increasing levels of nutrients there tends to be a move from rivers dominated by macrophytes (rooted) to algae

54
Q

Impacts of herbicides and insecticides

A

Herbicides
- weed control in crops

Insecticides

  • Crop pests
  • Livestock treatment for worms
  • Sheep dipping for ectoparasites

Impacts:

  • Death of natural plants; invertebrates; fish
  • Potential increase in more tolerant organisms
55
Q

Best management practices to protect water courses from agricultural activities

A 
Decrease ploughing in autumn
Delay ploughing in crop residue (winter stubble)
Sow autumn crops early
Sow cover crops in winter
Carefule storage of farm wastes
Decrease amounts of fertiliser, manure &amp; sewage applied
Leave minimum 10m buffer zone
Fence off livestock

CXB Ecological Systems (11 decks)

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