Site degradation

Question 1

Typical chars of bc soils

Answer 1

• Forest soils have developed since last ice age +/- 10,000 years • In BC mostly from glacial till
• Physical, chemical, biological processes altered the parent material (+/- 1m) and turned it into soil
• Typical rooting depth 60 cm or less

Question 2

Compaction vs puddling

Answer 2

• Compaction is an increase in soil density from applied forces (weight and vibration)
• Puddling is the destruction of soil structure and loss of macropore space (when soil is wet)
• Compaction lasts a long time (20+ years) • Can cause regeneration delay (50% > density = 25% less growth)
• Increased surfaced erosion

Question 3

What soil chars effect compaction?

Answer 3

• Coarse fragment content
• Texture
• Soil Density
• Soil Moisture
• Humus thickness

Question 4

What is displacement (aka scalping)

Answer 4

• Moving or burying of productive soil
• Caused by blading or stump removal during trail construction
• Occasionally by cable yarding
• Why a problem?

– Exposes poorer denser soils – Buries productive topsoils – More susceptible to erosion

Question 5

What soil type is at highest risk of compaction?

Answer 5

Silt loam or silty clay loam

High clay actually resists compaction in some cases

Question 6

What is surface erosion?

Answer 6

Loss of soil through water transport

• Natural forest soils rarely have overland water flow except in streams and gullies
• Compaction can cause overland water flow by damaging the infiltration capacity of the soil
• Compacted areas with exposed mineral soils become a major source of sediment
• Water is intercepted by road cuts and ditches
• Fill slopes are often over steepened and supported by wood

Question 7

What are most forestry wasting events resultant of?

Answer 7

Roads

Question 8

Where is the most productive part of the soil horizon?

Answer 8

Top 30 cm

Question 9

When is wasting considered to cause more risk?

Answer 9

• Proximity to streams
• Slope steepness
• Low soil permeability

Question 10

What are some strategies to avoid degradation?

Answer 10

• Road design
• Layout and boundaries – Good deflection – Windfirm boundaries – Riparian reserves
• Yarding – Control debris (streams) – Time of year (dry soils)

Question 11

What are some strategies to avoid deg on backspar trails?

Answer 11

• Leave forest floor intact
• Don’t excavate; or plan to rehabilitate
• Minimise trail width • Cut stumps low to avoid digging
• Outslope trails, waterbars
• Avoid wet areas
• Use lots of slash and remove later

Question 12

What are some road design tactics to reduce wasting on poor soils or steep slopes

Answer 12

Full bench cut and end haul to eliminate placement of fill on slope or running surface.

Question 13

Some plant indicators of instability?

Answer 13

Skunk cabbage, sedge, Indian hellebore, Devils club.

Question 14

How can skidding damage be mitigated?

Answer 14

• Designate Skid trails!!! – On moderate sites – Where multiple entries
• Use low ground pressure machines
• Skid when soil is dry or frozen
• Run machine on slash • Keep blade up

Question 15

How can deg be minimized during mechanized harvesting

Answer 15

• Minimize number of passes
• Avoid wet areas
• Use slash
• Dry or frozen soil conditions

Question 16

What is soil degradation?

What are some results?

Answer 16

• Definition - A reduction in the long-term soil productivity by management practices

– Causes lower forest productivity – Reduced water quality – Damage to fish and wildlife habitat – Reduced visual quality

• It is loss within the net area to reforest (i.e. not permanent access structures)