Understory species canopy cover under a range of overstory canopy covers in Plant Community 1, Native Forest. “Overstory” canopy cover includes tall overstory, midstory, and tree fern layers.
Understory Species Canopy Cover as a function of Overstory Canopy Cover
Overstory Canopy Cover Percent
`ohi`a lehua (seedlings & saplings)
kopiko (seedlings & saplings)
pandanus (seedlings & saplings)
State 1, Plant Community 1, Native Forest plant community.
State 2 – Mixed Native/Alien Forest
This state consists of one plant community. Native ohia trees still dominate the overstory. However, alien trees, shrubs, vines, and ferns make up a large portion of the lower parts of the plant community. Alien ferns (especially scaly swordfern), melastome shrubs, and strawberry guava produce a dense layer of low vegetation that severely inhibits reproduction of native species. This brings about eventual loss of native overstory, midstory, and tree fern canopies as well as smaller plants. Most native species are still present in this plant community but are much less abundant than in the Native Forest plant community. Activity of feral pigs further reduces native plant abundance and produces bare, disturbed soil patches.
Pathways from this state
To State 1 – Native Forest, via “C&D”:
C = feral pig exclusion; D = weed control.
It is possible to restore Mixed Native/Alien Forest to a plant community resembling Native Forest. Pig-proof fence and removal of pigs is necessary. Intensive weed control must then be carried out. In some cases, this may entail removal of large amounts of weed biomass from the site.
To State 3, Alien Forest, via “A&B&E”:
A = gradual weed invasion; B = feral pig damage; E = lack of native plant reproduction.
Aggressive, fast-growing weeds inhibit reproduction of native plants and gradually replace them. This process is accelerated by feral pigs directly damaging native plants and promoting the spread of weeds by disturbing the soil and spreading weed seeds.
To State 4, Grassland, via “G&H”:
G = land clearing; H = pasture establishment.
Mixed Native/Alien Forest can be converted to Grassland by clearing the forest with heavy machinery and planting desirable pasture species. Native forest may be cleared gradually by allowing cattle access to the forest. Cattle eventually eat or destroy understory ferns, forbs, shrubs, and saplings, opening up the forest so that pasture grasses will thrive. On shallow soils over lava substrates, underlying lava rock often is ripped and crushed by heavy machinery. Ripping and crushing produces some fine mineral particles and small, abundant gaps between the rock fragments. When this is done on organic soils, about 50% of the soil organic matter may be lost in the process due to exposure to air and higher temperatures.
Composite representation of State 2, Plant Community 2, Mixed Native/Alien Forest.