State 1
Reference

Community 1.1
Bishop pine/lemonade sumac-scrub oak

Figure 3. Bishop pine (Pinus muricata) forest

The most successionally-advanced community phase observed for the reference state is a Bishop pine (Pinus muricata) forest. Bishop pine has a canopy cover of 55 to 80% with the main overstory of trees ranging from 50 to more than 80 years in age. The understory varies depending on location on the island, changes in aspect, and overstory canopy cover. The most common understory species are lemonade sumac (Rhus integrifolia), summer holly (Comarostaphylis diversifolia), toyon (Heteromeles arbutifolia), and Channel Island scrub oak (Quercus pacifica).

Forest overstory.Canopy cover of Bishop pine (Pinus muricata) ranges from 30 to 80 percent, with canopy height usually between 25 to 30 feet. The trees are densely spaced, thin, and scraggly looking. Tree cores were not taken, so the age and site index is unknown. <br /> <br /> The table below represents percent canopy cover not percent production. The proper table is being developed.<br />

Forest understory. The understory cover is often high and ranges from 20 to 75 percent. In addition to the species mentioned above, common understory shrubs also include island manzanita (Arctostaphylos insularis), dwarf chaparral broom (Baccharis pilularis), feltleaf ceanothus (Ceanothus arboreus), Bishop pine (Pinus muricata), and hollyleaf cherry (Prunus ilicifolia ssp. lyonii). There is a diversity of plants on the forest floor. The most common species were roundfruit sedge (Carex globosa), redflower buckwheat (Eriogonum grande var. grande), coastal woodfern (Dryopteris arguta), and monkeyflowers (Mimulus spp.).<br />

Community 1.2
Bishop pine/lemondate sumac-scrub oak

Figure 4. Decling Bishop pine.

Bishop pines may begin to decline after approximately 60 years of age. The aging pine becomes more susceptible to drought and pest infestations resulting in a generally high cover of dead and dying trees in the area. Live Bishop pine canopy cover is usual less than 25 percent. Other common species found in this community includes lemonade sumac (Rhus integrifolia) and Channel Island scrub oak (Quercus pacifica).

Community 1.3
Lemonade sumac-scrub oak/Bishop pine

This community is temporarily dominated by shrubs, such as lemonade sumac and Channel Island scrub oak. These chaparral species remain an important component in the area, and may create competition with the Bishop pine seedlings and saplings. Bishop pine will regenerate as the dropped cones open and disperse seeds on the forest floor. The timing of seeding is spread out as the cone population opens over a multi-year period. In general, the trees in this community will be up to 20 years in age with up to 45% canopy cover. After the 1986 to 1991 drought, the Bishop pines regenerated prolifically from seed after the death of the overstory canopy. The mid-canopy of shrubs and the understory of forbs may have remained relatively undisturbed (Walter and Taha 2000).

Community 1.4
Bishop pine/lemonade sumac-scrub oak

This community is an intermediate phase with a mix of young Bishop pine and chaparral. The Bishop pine saplings seen in community phase 1.3 have begun to over-top the shrubs, and will eventual grow to the forest seen in CP 1.1. The tree age in this community phase ranges from 20 to 50 years, and the canopy is generally 35 to 60 percent Bishop pine cover. In some areas where shrubs are not well represented, a very dense forest of even-aged Bishop pine may develop with many young, somewhat spindly trees.

Community 1.5
Lemonade sumac-scrub oak/Bishop pine

In the unlikely event of a fire, a post-fire Bishop pine regeneration community may form. The composition of this community is dependent upon many variables, but most important are the stand age and burn intensity. Low intensity burns have higher seed survival, and thus greater regeneration of Bishop pine. High intensity burns, have higher seed mortality, making the young and over-mature stands of communities 1.2 and 1.3 most at risk. Regeneration can be dense and even-aged, with high seedling establishment, and canopy cover can reach up to 65 percent. In general, the trees in this community will be up to 20 years in age.

The impact and regeneration of chaparral species is related to fire intensity, but very little research can be found concerning the fire effects on the island’s chaparral species. Historical evidence from the nearby Santa Monica Mountains indicates that when chaparral burns, fires are very intense and difficult to control (Keeley, 2002). When fires are ignited early in the season they tend to remain small in size. However, the Santa Ana winds in the fall can spread fires rapidly and cover large areas. Fire in this community almost always burns the entire canopy, and so it is very unlikely it would remain a surface fire. Channel Island scrub oak (Quercus pacifica) will likely resprout from the root crown, while other species may produce seedlings. Post-fire conditions result in less potential competition of shrubs with Bishop pine assuming pine seedlings germinate within a year or so and follow their characteristic of growing rapidly.

Pathway 1.1a
Community 1.1 to 1.2

Bishop pine/lemonade sumac-scrub oak

Bishop pine/lemondate sumac-scrub oak

Severe drought and pathogens can shift community phase 1.1 to phase 1.2. Although Bishop pines can exceed 80 years in age, they typically succumb to pathogens at about 60 to 80 years old; drought conditions may weaken the trees and make them susceptible to insect and fungal infestations. The drought from 1986 to 1991 and a subsequent related beetle infestation caused severe mortality of the older Bishop pine stands. The impact of the drought on the associated chaparral species is not known, but chaparral species tend to be more drought-tolerant and would probably survive or even become established during this drought period.

Pathway 1.1b
Community 1.1 to 1.5

Fire may also shift CP 1.1 to CP 1.5, but lightning and natural fires are rare on the Channel Islands, and therefore the effects of fire on the Bishop pine community is unclear. Bishop pine may be able to regenerate from seed after a fire, depending upon the fire severity, which would create a post-fire Bishop pine regeneration community.

Pathway 1.2a
Community 1.2 to 1.3

On Santa Cruz Island Bishop pine is capable of regeneration in the absence of fire, shifting CP 1.2 to CP 1.3. As trees began to age, branches loaded with unopened or partially opened cones fall to the ground from the dead and dying trees. The cones that are removed from the tree are more likely to open, since the surface is warmer than on the exposed branches which are subject to wind and fog. The cones open and initiate Bishop pine regeneration (Community Phase 1.3) in the absence of fire.

Pathway 1.2b
Community 1.2 to 1.5

Lightning and natural fires are rare on the Channel Islands, and therefore the likelihood of fire and movement to community phase 1.5 is low. In the unlikely event of a fire, seeds unconsumed during the fire may initiate a post-fire Bishop pine regeneration, shifting phase 1.2 to phase 1.5.

Pathway 1.3a
Community 1.3 to 1.4

If given an extended period of time without disturbance from pests, grazing, and fire, community phase 1.3 will continue to grow, eventually shifting this site to the young Bishop pine forest seen in community phase 1.4.

Pathway 1.3b
Community 1.3 to 1.5

Lightning and natural fires are rare on the Channel Islands, and therefore the effects of fire on the Bishop pine community phase is unclear. In the unlikely event of a fire, seeds unconsumed during the fire may initiate a post-fire Bishop pine regeneration, shifting community phase 1.3 to community phase 1.5.

Pathway 1.4a
Community 1.4 to 1.1

After an extended period of time without disturbance, Bishop pine will continue to grow, eventually creating more canopy cover over the shrubs and shifting community phase 1.4 to the forest seen in community phase 1.1.

Pathway 1.4b
Community 1.4 to 1.5

Lightning and natural fires are rare on the Channel Islands, and therefore the likelihood of fire on the Bishop pine community phase is low. In the unlikely event of a fire, seeds unconsumed during the fire may initiate a post-fire Bishop pine regeneration, shifting community phase 1.4 to community phase 1.5.

Pathway 1.5a
Community 1.5 to 1.4

Pine seedlings and saplings continue to progress and begin occupying an overstory dominant position. Development moves towards community phase 1.4.

State 2
Altered State (Chaparral)

Community 2.1
Lemonade sumac-summer holly-toyon-scrub oak

This community phase is dominated by a chaparral shrubland with a canopy cover of less than 25 percent. Due to the decimation of a Bishop pine seed source, pine regeneration is not expected. Common chaparral species may include lemonade sumac (Rhus integrifolia), summer holly (Comarostaphylis diversifolia), toyon (Heteromeles arbutifolia), and Channel Island scrub oak (Quercus pacifica).

Community 2.2
Lemonade sumac-summer holly-toyon-scrub oak

From a reference state community phase, this altered state community phase can develop due to a severe fire and/or prolonged grazing whichs causes high Bishop pine tree and seed mortality. This disturbance will halt the Bishop pine regeneration seen in the Reference State and lead to a community dominated by chaparral species. Common chaparral species include lemonade sumac (Rhus integrifolia), summer holly (Comarostaphylis diversifolia), toyon (Heteromeles arbutifolia), and Channel Island scrub oak (Quercus pacifica). Initially, grasses and forbs dominate while the canopy is open during the first couple of years following a fire. Most of the dominant shrub species are able to rapidly recover and grow after a fire.

Pathway 2.1a
Community 2.1 to 2.2

In the unlikely event of a fire, community phase 2.1 will shift to community phase 2.2. Lightning and natural fires are rare on the Channel Islands, and therefore the probability of fire is low. Historical evidence from the nearby Santa Monica Mountains indicates that when chaparral burns, fires are very intense and difficult to control (Keeley, 2002). When fires are ignited early in the season they tend to remain small in size. However, the Santa Ana winds in the fall can spread fires rapidly and cover large areas. Fire in this community phase would almost always burn the entire canopy, so it is very unlikely it would remain a low-intensity surface fire.

Pathway 2.2a
Community 2.2 to 2.1

If given an extended period of time without disturbance from fires or grazing, community phase 2.2 will develop into the shrubland seen in community phase 2.1. Channel Island scrub oak (Quercus pacifica) will likely resprout from the root crown, while other species may produce seedlings. As the shrubs continue to increase in size and cover, they will eventually shade out the grasses and forbs in the understory creating a chaparral shrubland.

Transition T1
State 1 to 2

Transition to State 2 (typically community phase 2.2) occurs after severe fire, and/or prolonged grazing. Severe fire during the later stages of community development can cause high tree and seed mortality, leaving little opportunity for Bishop pine regeneration and likely its exclusion as a species in the state’s community phases. In addition, heavy grazing on Bishop pine seedlings and saplings for long durations inhibits successful regeneration of Bishop pine. If regeneration does not occur before the stand dies of old age, Bishop pine will decline.

Restoration pathway R2
State 2 to 1

Restoration to move the Altered State back to the Reference State is feasible but would require substantial time and financial input. It is unknown at this time how much area of the Channel Islands may have had Reference State Bishop pine forests. Regardless of historic or more recent transitions to the Altered State, Bishop pine seedlings of an acceptable seed source would need to be reintroduced and protected from herbivory, shrub competition and frequent fire.