Best practices for reducing harvest residues and mitigating mobilisation of harvest residues in steepland plantation forests.
Type of content
Summary: Plantation forestry in New Zealand covers approximately 7% of NZ’s total land area with 28 million m3 of timber expected to be harvested in 2018. The majority of timber harvest is from Pinus radiata (‘radiata’) plantation forests grown 25-30 years. Approximately 40% of the plantation estate is on steeper and or erodible terrain, driven mainly by the lower land values for forest conversion but also the benefits of stabilising erosion prone land with trees. The current preferred harvesting practice in New Zealand is larger scale clear-cutting, based on logistical and economic benefits, but also on planting regimes whereby whole catchment areas are planted in a short time-frame. Although certainly not new, recent larger scale debris flow events with entrained harvesting residues has caused significant damage to downstream land use. This includes inundation of land with sediment and slash, damage to infrastructure including roads, bridges and homes, or the deposition of woody debris on beaches. A number of events have occurred in the Gisborne Region resulting in significant flooding, but also large scale deposition and damage from harvest residues on the regions’ rivers and beaches, coinciding with recent extensive harvesting within the catchments. Similar events have also occurred in Northland, Coromandel, Bay of Plenty and Nelson-Marlborough. These events are prompting Regional and District Councils to review the acceptability of current forestry practices and to identify opportunities for improvement. The report focusses on the relationship between harvesting, harvest residues, and the best practices that help mitigate debris flow events and or the delivery of harvest residue.
Ngā upoko tukutuku/Māori subject headings
ANZSRC fields of research
Fields of Research::30 - Agricultural, veterinary and food sciences::3007 - Forestry sciences::300707 - Forestry management and environment