State 1
Reference State

The Reference State consists of one plant community. Under a regime of natural disturbances, this community has probably been stable through post-glacial time frames and from a broad-scale spatial perspective. A matrix of variations in canopy cover and species composition in all canopy levels is observable. This matrix variability does not appear to be connected to soils, climate, or landscape features, but rather is probably due to wind throw, deaths of large trees, and other chance occurrences.

Community 1.1
`Ohi`a lehua - koa/hapu`u/kanawao

Figure 7. Reference State 7/15/04 D Clausnitzer MU514

Figure 8. View above hapuu canopy 8/6/04 D Clausnitzer MU515

Figure 9. View above hapuu canopy 8/17/04 D Clausnitzer MU515

Figure 10. View below hapuu canopy. No date, D Clausnitzer, no location.

Figure 11. View at ground level 9/9/05 D Clausnitzer MU512

This community phase is a forest consisting of four canopy strata: an open or closed upper canopy of ohia lehua or ohia lehua and koa up to 100 feet (30 meters) tall, a secondary canopy of diverse tree species 30 to 60 feet (9 to 18 meters) tall, a dense tree fern canopy 10 to 30 feet (3 to 9 meters) tall, and a diverse understory of shrubs and ferns. Vines, particularly ieie, are common both on the ground and on trees. These forests have standing live timber of 300 to 5900 cubic feet per acre, with a representative value of about 5000 cubic feet per acre. Typical low values are about 1500 cubic feet per acre. The lowest values of 300 to 800 cubic feet per acre on steep, continually eroding soils, and in the drier extremes of this ecological site. Canopy cover of ohia lehua and koa in the upper canopy varies on the microscale from about 10% to 80%, with a representative value of 40 to 50% on a macroscale. Secondary canopy cover of medium-stature tree species is typically about 20%, concentrated in the 30 to 40 feet (9 to 12 meters) height range. Cover of the tertiary tree fern canopy is usually in the range of 60% to 90%, mostly between 13 to 20 feet (4 to 6 meters) tall. Koa and ohia lehua do not reproduce successfully in the shady understory of intact forest. Tree ferns, medium-stature tree species, and shrubs reproduce and grow well in the understory. The ground layer of small ferns is typically dense and diverse in the absence of introduced ungulates. A heavy litter layer that appears to inhibit establishment of small plants is usually present on the soil surface. In particular, dead tree fern fronds produce a coarse, thick, heavy litter layer. Koa phyllodes create a firm, continuous litter layer. Phyllodes are petioles (leaf stalks) that are adapted to function as leaves on mature koa trees.

Forest overstory. The uppermost forest canopy consists of ohia lehua or a combination of ohia lehua and koa. There seems to be no consistent relationship between dominant tree canopy composition and soil type, rainfall, elevation, or any other environmental variable. Neither overstory species grows well in shade. Primary succession in Hawaii typically results in an initial forest overstory of ohia lehua, often consisting of roughly even-aged cohorts. It is likely that long-term disturbance history controls koa occurrence. Koa is a fast growing, opportunistic species that is able to take advantage of temporary openings in the forest canopy. Wind fall, nearby lava flows, or death of ohia lehua population cohorts would provide the conditions for koa expansion where their seeds are present. Koa also can reproduce by sprouting from near-surface roots.

Forest understory. The most common secondary canopy tree species are olapa or olapalapa (Cheirodendron trigynum), kolea lau nui (Myrsine lessertiana), olomea (Perrottetia sandwicensis), and pilo (Coprosma spp.). The palm native to this ecological site, loulu (Pritchardia lanigera), is rare but may have been more abundant in the past.

The tertiary canopy contains small trees but is dominated by three species of hapuu or tree ferns: hapuu (Cibotium glaucum), hapuu ii or hapuu li (Cibotium menziesii), and hapuu or Chamisso’s manfern (Cibotium chamissoi). Cibotium glaucum is the most abundant, followed by C. menziesii; C. chamissoi is the least abundant.

The lowest canopy stratum, which ranges in height from the ground to about 4.5 feet (1.5 meters), consists of seedlings and immature individuals of species in the taller strata, small shrub species, forbs, vines (some prostrate, some climbing, some both), sedges, and over 30 species of ferns and fern allies.

State 2
Naturalized Grassland State

This state is comprised of three community phases. Most of the grasslands are on former sugar plantations where guineagrass was an agricultural weed. Guineagrass now has taken over these lands as the dominant species. Kikuyugrass is the dominant grass, sometimes with pangolagrass, in some higher elevation areas where these species have been planted. Most of these areas are now being reforested. Some parts of Kapapala Ranch appear to be in a transitional area between guineagrass and kikuyugrass dominance. Information on these kikuyugrass/pangolagrass pastures can be found in Ecological Site Description F160XY504 Ustic-Dry Udic Forest. This state consists of three grassland community phases. These phases are maintained by grazing, which keeps preferred species from becoming too tall, and adequate recovery periods, which ensure vigor and cover of preferred species. High production of preferred grass species and extensive cover allow for increased soil moisture retention, vegetative production, and overall soil quality. These factors are degraded by grazing practices that result in loss of preferred grass species leading to increase in less desirable grasses, weed invasion, and an increase in the extent of bare soil. Prescribed burning generally is not allowed due to high risks to structures, fences, and native forest stands. Wildfires caused by lightning or arson sometimes occur. They are very intense and difficult to contain, because guineagrass produces huge amounts of fuel and grows to a height of almost 10 feet (3 meters), while kikuyugrass produces large amounts of fuel and has rhizomes that can smolder underground for days, sometimes reigniting a surface fire. Most of the grasslands in this ecological site are on former sugar plantations where guineagrass (Urochloa maxima) was a species of roadsides and waste areas (Earl Spence, rancher and manager, personal communication). Guineagrass now has taken over these lands as the dominant forage grass. All grass, sedge, forb, vine, shrub, and tree species found in this state have been introduced to Hawaii by humans within the past two centuries, either inadvertently or intentionally. Scattered, remnant native trees, either koa or ohia lehua, sometimes occur in these naturalized grasslands, but they are unable to reproduce without protection from ungulates and control of grasses and weeds. Occasionally, western brackenfern (Pteridium aquilinum) and uluhe or Old World forkedfern (Dicranopteris linearis) occur; both of these fern species are native to Hawaii. Community Phase 2.1 mostly consists of guineagrass, sometimes with an admixture of glycine or perennial soybean (Neonotonia wightii). Continuous grazing that does not allow the preferred forage species to recover from defoliation results in Community Phase 2.2, which is dominated by lower value grass species but contains enough remnant guineagrass to allow for a shift back to Plant Community 1 with prescribed grazing. Longer-term continuous grazing leads to Community Phase 2.3, which consists of low value grass species and increasing cover of alien shrubs and tree saplings. Improvement of this Plant Community requires weed control followed by prescribed grazing.

Community 2.1
Guineagrass - kikuyugrass/glycine

Figure 12. Guineagrass grassland makai of Kau SF, D Clausnitzer, generic photo.

Figure 13. Grazed guineagrass, Kau SF boundary, D Clausnitzer, generic photo.

The dominant grass species in this pasture type is guineagrass that has volunteered in old sugarcane plantations. In higher elevation areas in Kahuku and Keauhou, kikuyugrass and sometimes pangolagrass have been planted. Guineagrass is very productive and nutritious for livestock. Careful management of this caespitose (bunch-forming) grass is required to maintain it at an efficient height (two to four feet) while maintaining sufficient ground coverage by leaves, litter, and grass clumps to protect the soil from erosion and to suppress weed growth. The normal total annual production (all types and species of plants) of the grasslands in this community phase is about 14,000 lb/acre of forage. Above normal production is about 16,000 lb/acre; below normal production is about 10,000 lb/acre).

Forest understory. This community phase is not forest, despite the automated default heading printed above this section, but rather a naturalized grassland that occurs where forests have been cleared.

Guineagrass is very competitive with other plants when properly managed and can comprise 85 to nearly 100% of the total production on a site. Forbs, shrubs, tree seedlings, and other grass species can occur in the interspaces between guineagrass bunches but are insignificant in their share of total production in well-managed sites. They are kept in check by competition with guineagrass and foraging and trampling by livestock. Perennial soybean or glycine (Neonotonia wightii), a competitive (and potentially weedy in forests), climbing legume vine, and three-flowered ticktrefoil (Desmodium triflorum), a prostrate legume, are desirable forage species that can be maintained within guineagrass stands by careful grazing management.

Community 2.2
Hilograss - carpetgrass

Figure 15. Grassland with low value grasses. D Clausnitzer, makai of Kau FR, generic photo.

This community phase is dominated by grass and grasslike species with lower forage value than guineagrass. Cattle can be maintained on these forages, but animal growth and vigor will be reduced. Also, the number of weedy species is high, and their stature, seed production potential, and wide distribution can lead to rapid increase and a shift to Community Phase 2.3 unless management is improved.

Forest understory. The most abundant grasses are hilograss (Paspalum conjugatum), common carpetgrass (Axonopus fissifolius), and shortleaf spikesedge (Kyllinga brevifolia), all of which have lower stature and are much less productive than guineagrass. Significant amounts (around 20% canopy cover) of guineagrass remain, but it is grazed low and is scattered across the site. Desirable forage legumes have been grazed out. Height of weedy trees, shrubs, ferns, vines, and forbs is low, and the combined cover of all these species is about 5 to 20%.

Community 2.3
Common guava - christmasberry/sourbush/broomsedge - beardgrass

Figure 16. Grassland invaded by woody species 4/25/06 D Clausnitzer MU553.

This community phase is dominated by grass species with little or no forage value. Guineagrass typically comprises a small portion (roughly 5% canopy cover) of the grasses present, but sometimes is more abundant but of low stature. Spiny forbs and vines are common, as are a large number of forb and fern species with little or no forage value. Introduced shrubs and small trees are common, and seedlings and saplings of large, introduced tree species are present. Bare soil is 10% or more of the ground surface. The abundance of immature trees with potential mature heights of 20 to over 100 feet (6 to over 30 meters) presents a strong risk of losing the grassland to weedy forest. Improving the grazing regime is extremely unlikely to shift this phase to a more productive grassland phase due to the abundance of weeds. Frequent mowing is not worthwhile; it will keep shrubs and trees in check but will do little to improve the grass and forb community. Herbicide treatments are needed to reduce weed abundance. Reseeding of guineagrass may be needed, along with removal of livestock until guineagrass has reassumed dominance.

Forest understory. Hilograss, common carpetgrass, broomsedge bluestem (Andropogon virginicum), and beardgrass or Colombian bluestem (Schizachyrium condensatum) are the most abundant grasses. Sawtooth blackberry (Rubus argutus), yellow Himalayan raspberry (Rubus ellipticus), and West Indian raspberry or thimbleberry (Rubus rosifolius) form small thickets. Shrubs such as cure for all or sourbush (Pluchea carolinensis), along with small trees such as common guava (Psidium guajava) and christmasberry or Brazilian peppertree (Schinus terebinthifolius) have combined canopy cover of about 20% and heights of 2 to 4.5 feet (0.5 to 1.5 meters). Seedlings and saplings of large tree species such as octopus tree (Schefflera actinophylla) and albizia or peacocksplume (Falcataria moluccana) are often present.

Pathway 2.1A
Community 2.1 to 2.2

Guineagrass - kikuyugrass/glycine

Hilograss - carpetgrass

Community phase 2.1 degrades to phase 2.2 by continuous grazing that weakens preferred guineagrass or kikuyugrass and legumes in relation to less desirable forage species such as hilograss, common carpetgrass, and sedges.

Pathway 2.2A
Community 2.2 to 2.1

Hilograss - carpetgrass

Guineagrass - kikuyugrass/glycine

Community phase 2.2 can be reconverted to phase 2.1 by prescribed grazing. A prescribed grazing plan provides for intensive but temporary grazing of pastures that ensures that cattle consume some low-value forage species along with preferred forages and allows preferred forages time to recover from defoliation. The grazing plan may require splitting the herd, creating additional water sources, and creating multiple pastures by cross-fencing. Invading broomsedge and beardgrass may be controlled by mowing their seed stalks before seed set and by liming to increase soil pH.

Pathway 2.2B
Community 2.2 to 2.3

Hilograss - carpetgrass

Common guava - christmasberry/sourbush/broomsedge - beardgrass

Community phase 2.2 degrades to phase 2.3 by long-term continuous grazing. Guineagrass cover is greatly reduced and largely replaced by lower-value forage grasses. Weedy forbs such as spiny amaranth, introduced blackberries, and introduced shrubs such as sourbush have increased. Broomsedge and beardgrass often are the most abundant grass species.

Pathway 2.3A
Community 2.3 to 2.1

Common guava - christmasberry/sourbush/broomsedge - beardgrass

Guineagrass - kikuyugrass/glycine

Community phase 2.3 can be converted to phase 2.1 by a combination of weed control and prescribed grazing. Weeds such as introduced blackberries, sourbush, and spiny amaranth are not controllable by domestic livestock and must be killed with herbicide. The grazing prescription will require removal of livestock from the pasture until guineagrass has reestablished adequately to support grazing. Thereafter, the grazing plan may require splitting the herd, creating additional water sources, and creating multiple pastures by cross-fencing.

Pathway 2.3B
Community 2.3 to 2.2

Common guava - christmasberry/sourbush/broomsedge - beardgrass

Hilograss - carpetgrass

Herbicidal weed control measures, liming, and mechanical brush control can reduce the densities of weedy shrubs, forbs, and grasses. However, these measures alone will not bring about guineagrass dominance without changes in the grazing regime.

State 3
Planted Timber State

This state consists of one community phase, which is a plantation of introduced timber tree species that have been established on former sugarcane or grazing lands. With typical management, it is not susceptible to unplanned transitions or restorations to other states.

Community 3.1
Exotic timber trees/guineagrass

Figure 17. Eucalyptus plantation mauka of Pahala, D Clausnitzer, generic photo.

This community is typically managed in the long term for economic returns. Many introduced timber species will potentially grow well in the environment of this ecological site, where they also may be free of pests that are present in their native habitats.

Forest overstory. Various species of Eucalyptus are most commonly planted, including hybrids (primarily E. grandis x urophylla), grand eucalyptus (E. grandis), rainbow gum (E. deglupta), red gum (E. robusta), and blue gum (E. saligna). Other valuable species can be planted, including African mahogany (Khaya senegalensis), Honduran mahogany (Swietenia microphylla), toon or Australian red cedar (Toona ciliata), and Spanish cedar (Cedrela odorata). Other species are also possible. Consult with NRCS, the University of Hawaii Extension Forester, or a private consultant to ensure that noninvasive species are selected and that species are planted in suitable elevation ranges. Few introduced timber species are suitable for the full elevation range of this ecological site.

Koa is a valuable, fast-growing native tree that can be planted on these sites. It is much more likely to thrive at elevations higher than about 1500 feet (460 meters); lower elevation plantings are often subject to diseases. Feral and domestic animals must be fenced out of koa plantations for enough years to allow the trees to attain a stature at which animals are unable to push down and eat them. Trampling of koa’s shallow roots and eating the trees’ bark can remain a problem for a longer time. There are examples of adequately mature koa stands being maintained along with careful cattle grazing in silvopastures.

Forest understory. Guineagrass is usually abundant beneath the timber trees; despite being shaded by trees, it can form a nearly continuous canopy cover and attain heights of 3 to 4.5 feet (1 to 1.5 meters). Guineagrass appears to be partially suppressed beneath mature stands of Eucalyptus species, possibly due to the density and chemical composition of the tree litter. Strawberry guava can form dense stands beneath any timber species.

State 4
Invaded Understory State

This state consists of one community phase. It arises by invasion by introduced species of intact native forest (the Reference State) or, in some cases, of native overstory stands from which the original understory has been cleared. Native species are unable to regenerate in the highly competitive understory of introduced plants and eventually die out. With time, large introduced tree species will emerge to replace the native overstory trees and form a new overstory. When this last step has occurred, the site will have transitioned to State 5, Invaded Overstory and Understory State. Disturbance of the soil and direct damage to native understory plants by introduced ungulates, particularly pigs and cattle, will speed the transition to this state by killing native plants and by creating better germination sites for introduced species. Restoration to the Reference State or a facsimile of it is possible by fencing the site, removing all ungulates, applying herbicides, and replanting native species when needed. Restoration efforts will be affected depending on the degree of invasion by introduced species and by the particular species that have invaded the site. Long term weed management and fence maintenance will be necessary.

Community 4.1
Koa - `ohi`a lehua/strawberry guava/kahili ginger

Figure 18. Weed-invaded understory, Kau SF, D Clausnitzer, generic photo.

Figure 19. Pig damage to soil surface. D Clausnitzer, generic photo.

The community has an intact or diminished overstory of large ohia lehua and/or koa trees with a dense understory of introduced shrubs, ferns, vines, grasses, and small trees.

Forest overstory. The overstory consists of ohia lehua and/or koa. Secondary canopy native species are usually somewhat diminished. Wild coffee or kopiko (Psychotria spp.) is usually the most common native species remaining in the secondary canopy.

Forest understory. The only native species remaining in the lower canopy levels are a few hapuu (Cibotium glaucum) or hapuu li (Cibotium menziesii), and traces of small wild coffee or kopiko, some peperomia (Peperomia spp.) at ground level, an occasional ieie vine (Freycenetia arborea), and a few patches of uluhe or Old World forkedfern. Some small native fern species may be found growing on trees.

The understory is usually dominated by a nearly impenetrable stand of strawberry guava or waiawi (Psidium cattleianum), which is usually 10 to about 30 feet (3 to 9 meters) tall. Other species indicated on the table grow sparsely beneath the strawberry guava or fill in gaps between it.

State 5
Invaded Overstory and Understory State

This state is comprised of one plant community dominated by introduced species in both the overstory and understory. Understory vegetation usually is very sparse to nonexistent. Remnant individuals of a few native species may persist. This state might be considered a dead end as far as further succession or transition to another state. Restoration to a facsimile of the Reference State could probably be done with expensive and intensive practices followed by long-term weed management. Clearing of the site followed by establishment of an overstory of noninvasive, introduced timber trees with a native understory as an intermediate step to native forest restoration may be worth exploring.

Community 5.1
Strawberry guava - christmasberry/kahili ginger

Figure 20. Albizia overstory with guineagrass understory. D Clausnitzer, generic photo.

It is possible that shifts will eventually occur in the introduced species that dominate the site, particularly if tall stature, competitive tree species are present. This would change the mix of species present and may affect soil chemistry (e.g. nitrate availability or organic matter), but would not represent a transition to another state. Sites that are completely dominated by dense stands of strawberry guava typically show no indications (death or partial death of stands; emergence of potentially taller tree species) of yielding to change in the foreseeable future.

Forest overstory. Depending on local seed sources, invasive trees of moderate stature including strawberry guava, christmasberry, or common guava can dominate a given site initially, but strawberry guava generally will become dominant over time. Taller statured introduced trees including silkoak (Grevillea robusta), albizia or peacocksplume (Falcataria moluccana), and octopus tree (Schefflera actinophylla) could potentially emerge through the canopy of moderate stature species.

A few remnant ohia lehua tree often remain as emergents above the canopy of introduced species, but no seedling or saplings are likely to be present.

Forest understory. The tree overstory species are highly competitive and produce dense shade. A variety of introduced understory species is often present but in small numbers. Typical species include Koster’s curse or soapbush (Clidemia hirta), kahili ginger or Kahila garland-lily (Hedychium gardnerianum), and some shade tolerant grass species.

Scattered individuals of remnant native species such as kopiko, hapuu, and uluhe may remain in the understory.

Transition T1A
State 1 to 2

State 1, Reference State, can transition to State 2, Naturalized Grassland, by clearing the forest with heavy machinery or by gradual clearing 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. Grasslands that were cleared by machinery may have broad cleared areas and isolated islands of trees that later grew in the shelter of slash piles. At higher, cooler elevations kikuyugrass and/or pangolagrass have been planted. At lower elevations where pastures are on old sugarcane plantations, guineagrass (a former weed in the plantations) has volunteered.

Transition T1A
State 1 to 2

Transition T1B
State 1 to 4

State 1, Reference State, can transition to State 4, Invaded Understory State, by gradual replacement of the native understory with introduced shrubs, vines, and small trees that outcompete the native understory species. This process is accelerated by ungulate foraging that disturbs the soil surface and directly destroys native plants and prevents their regeneration.

Restoration pathway R2A
State 2 to 1

It is possible to restore a facsimile of the Reference State from Naturalized Grassland. Weed control must be applied to grasses species and the many opportunistic plant species that will invade the site. Weed control is be a perpetual process to capture and maintain the site, with the intensity of control depending on the proximity of weed seed sources. Animal foraging (domestic and feral) must be eliminated by excluding all ungulates from the restoration site, but domestic ungulates would be useful to initially reduce grass cover and afterward to manage vegetation outside the restoration site perimeter. Extensive planting of native species would follow. Increased shade from trees growing on the site causes a shift from C4 (warm-season) grass dominance (typically guineagrass or kikuyugrass) to C3 (cool-season) shade-tolerant grasses, typically meadow ricegrass. Meadow ricegrass stands can be dense and detrimental to establishment of native plants. Attempts have been made to suppress meadow ricegrass by planting native shrubs and tree ferns that produce dense shade near the ground and litter that covers the grass. Biodegradable mulch such as cardboard covered with plant litter is very useful.

Transition T2A
State 2 to 3

State 2 Naturalized Grassland may be converted to State 3 Planted Timber State by mechanical site preparation and planting of timber species (usually eucalyptus) and weed control.

Transition T2B
State 2 to 5

Abandonment of State 2 Naturalized Grassland leads to rapid invasion by introduced tree species that take over from the initial growth of grasses and invasion of weedy forbs, vines, and shrubs. The most common tree species are silk oak, christmasberry, albizia, and common guava.

Restoration pathway R4A
State 4 to 1

It is possible to restore a facsimile of State 1 Reference State from State 4 Invaded Understory State. Before restoration of native plants, alien understory plants must be eliminated by herbicidal weed control practices, and ungulates must be excluded from the restoration site by a suitable fence. Native species that have been eliminated or greatly reduced in numbers must be restored by replanting. Biodegradable mulch such as cardboard covered with plant litter is very useful for weed control around replanted native species. Long-term control of weeds will be necessary.

Transition T4A
State 4 to 2

State 4 Invaded Understory State may be converted to State 2 Naturalized Grassland State by mechanical clearing of introduced and remnant native understory plants; native overstory trees may be harvested for timber, destroyed, or left for shade. If leaving large native trees for shade, care must be taken to not damage near-surface roots within about 20 feet of the trees. Introduced pasture grasses may then be seeded or sprigged into the site. Herbicide applications will be necessary before and during pasture establishment to control reemerging weed species.

Transition T4B
State 4 to 5

The large native ohia lehua and koa trees that form the overstory of State 4 Invaded Understory State are unable to successfully regenerate due to the very dense, shady understory of introduced species. Eventually the large native trees die and are replaced by introduced tree species.

Restoration pathway R5A
State 5 to 2

State 5 Invaded Overstory and Understory State may be restored to State 2 Naturalized Grassland State by mechanical clearing of overstory and understory vegetation. Introduced forage grasses may then be seeded or sprigged into the site. Herbicide applications will be necessary before and during pasture establishment to control reemerging weed species.