An article in the New Zealand Journal of Forestry discusses the current situation in New Zealand.
After logging operations, exposed soils can be unstable and more susceptible to erosion. Chris Phillips, Michael Marden and Les Basher of Landcare Research’s Erosion and Sediment Processes team, provide an opinion on the subject in the New Zealand Journal of Forestry (February 2012, Vol. 56, No. 4). Mature plantations provide protection against erosion. However, once they are logged, the site dynamics changes.
The article describes the relationship between forests and slope stability, and what happens when logging takes place and the trees are removed on steeper slopes. Plantation forests established on erodible steeper slopes are most prone to shallow landslides once the harvesting residue has broken down, but tree root systems and canopies have not yet become established. This period is termed the “window of vulnerability”, and large rainfall events during this period can result in higher soil erosion.
Logging equipment does not appear to contribute as much to reduced soil stability as earthwork activities for road and landing construction does. Soils are usually more moist than usual after harvesting, which increase the chances of landslides. The risks of soil erosion and landslides have been reduced in recent times due to improved planning, logging and roading practices, enforced by certification schemes such as FSC. Cable yarding systems and better landing placement have also lowered this risk. The use of riparian and other “set-aside” areas as buffers has reduced the risk further. A practice that could improve slope stability is increasing stand density, which would reduce the window of vulnerability.
The article then discusses what information is still required to make sure that forestry practices such as logging can show even further improvements. Source: http://www.nzjf.org/
After logging operations, exposed soils can be unstable and more susceptible to erosion. Chris Phillips, Michael Marden and Les Basher of Landcare Research’s Erosion and Sediment Processes team, provide an opinion on the subject in the New Zealand Journal of Forestry (February 2012, Vol. 56, No. 4). Mature plantations provide protection against erosion. However, once they are logged, the site dynamics changes.
The article describes the relationship between forests and slope stability, and what happens when logging takes place and the trees are removed on steeper slopes. Plantation forests established on erodible steeper slopes are most prone to shallow landslides once the harvesting residue has broken down, but tree root systems and canopies have not yet become established. This period is termed the “window of vulnerability”, and large rainfall events during this period can result in higher soil erosion.
Logging equipment does not appear to contribute as much to reduced soil stability as earthwork activities for road and landing construction does. Soils are usually more moist than usual after harvesting, which increase the chances of landslides. The risks of soil erosion and landslides have been reduced in recent times due to improved planning, logging and roading practices, enforced by certification schemes such as FSC. Cable yarding systems and better landing placement have also lowered this risk. The use of riparian and other “set-aside” areas as buffers has reduced the risk further. A practice that could improve slope stability is increasing stand density, which would reduce the window of vulnerability.
The article then discusses what information is still required to make sure that forestry practices such as logging can show even further improvements. Source: http://www.nzjf.org/