Earth:Pocket forest

a pocket forest has been planted in Danehy Park

A pocket forest or Miyawaki forest is created by planting native trees, shrubs and groundcover plants to form a canopy layer of tall trees, a shrub layer, and ground cover in small urban areas. The concept was pioneered by Japanese botanist Akira Miyawaki as a means of restoring native plant species in damaged ecosystems. The concept has been embraced by environmentalists as a means of teaching urban residents about native forest environments.

Methods

While forests naturally grow through a primary stage and then a secondary stage before reaching their climax stage, pocket forests are created by a dense planting of climax stage species which grow rapidly in competition for sunlight. The area to be planted is first covered with a layer of cardboard which is then covered with 3–6 in (7.6–15.2 cm) of compost and allowed to acclimate to local moisture conditions for several months. The covered area is then planted with year-old plant nursery saplings spaced approximately 2 ft (0.6 m) apart. The entire surface area should be planted at the same time with a variety of native species so no saplings of the same species are adjacent to each other. Watering is unnecessary for native plants acclimated to the local environment; although watering for the first few years after planting, and during drought periods, will reduce mortality of individual plants. Pocket forests planted with greater density than commercial timberland utilize edge lighting in addition to overhead lighting to grow faster while absorbing more carbon dioxide per acre.

Three is the minimum number of different species of nursery saplings for planting a pocket forest. The arrangement below of species A, B and C illustrates avoidance of planting the same species in adjacent positions.

  A   B   C   A
B   C   A   B   C
  A   B   C   A

Examples

• Pocket Forests CLG assists creation of pocket forests of 6–50 m² (65–538 sq ft) within urban areas of Ireland.
• The Yakama Nation has planted seven healing forests of 47 species totaling 23,000 sq ft (2,100 m²) on their corrections and rehabilitation facility to restore harmony to body, mind and spirit.
• A Miyawaki forest has been planted over a landfill in Cambridge, Massachusetts, as part of Danehy Park.
• A 1,000 sq ft (93 m²) forest has been planted as part of Griffith Park in Los Angeles .
• Several Miyawaki forests have been planted in Berkeley, California.
• A 770 m² (8,300 sq ft) pocket forest of 20 species is being planted in the City of Brussels.
• The town of Ayer, Massachusetts, organized community volunteers to plant a pocket forest.

Potential problems

Fire ecosystem comparison of heat-sterilized soil under white ashes from coals of burning wood, while underground plant structures like grass rhizomes have survived and sprouted beneath the lighter fuel concentration of adjacent burnt duff.

Miyawaki developed the method as a means of replenishing forest soils by allowing dead leaves and twigs to decompose in a moist, wood-rotting ecosystem. This process may be less successful in drier fire ecosystems where nutrients are recycled as ashes. The dense pocket forest forms a capture mechanism for wind-blown embers, dried ground litter is an ignition source, and the multi-layered pocket forest forms a fuel ladder with wildfire risks in urban areas.