5.2:Clearcutting

Learning Objective:

• Describe the effects of clearcutting on forests

Essential Knowledge Checklist:

• Clearcutting can be economically advantageous but leads to soil erosion, increased soil and stream temperatures, and flooding

Direct Effects of Clearcutting

Soil erosion:

• Caused by loss of stabilizing root structure

• Removes soil organic matter & nutrients from the forest

• Deposits sediments in local streams

Increased soil & stream temperature

• Loss of tree shade increases soil temperature

  • Soil has a lower albedo than leaves of trees

• Loss of tree shade along rivers & streams warms them

  • Erosion of sediments into rivers also warms them

Flooding & landslides

• Logging machinery compacts the soil

• increased sunlight dries out the soil

• Loss of root structure = erosion of topsoil & O horizon

  • All of these factors decrease H20 holding capacity of soil causing flooding & landslides

Tree Plantations

Tree Plantations: Areas where the same tree species are repeatedly planted, grown, and harvested

Lowers Biodiversity:

• Biodiverse, mature forests are replaced with single-species forests

• less species diversity = lower resilience

• Less habitat diversity for other organisms

All the same age:

• All trees are planted at the same time = all the same age

• Lowers biodiversity further (no dead trees for woodpeckers, insects, decomposers

Forest Benefits

1. Filtering of air pollutants

   • Stomata (leaf pores) remove VOCs, NO2, and PM from the air and store them in the tree

2. Removal & storage of CO2 from the atmosphere

   • Trees take in CO2, store carbon as sugar, wood, and other tissue & release O2

3. Habitat for Organisms

   • Many organisms live in forests (biodiversity, ecotourism)

Deforestation Consequences:

• Reduces air filtering and carbon-storing services

• cutting trees down releases CO2 from decomposition of leftover organic material

• Slash & Burn: Method of clearing land for agriculture by cutting trees & burning them releases CO2, N2O and water vapor into the atmosphere (all GHGs)