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Ecological site VX163X01X004

South and West Aspect Isohyperthermic Naturalized Grassland

Last updated: 5/08/2025
Accessed: 05/19/2025

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General information

Provisional. A provisional ecological site description has undergone quality control and quality assurance review. It contains a working state and transition model and enough information to identify the ecological site.

MLRA notes

Major Land Resource Area (MLRA): 163X–Alluvial Fans and Coastal Plains

This MLRA is in the State of Hawaii on the islands of Maui, Lanai, Molokai, Oahu, and Kauai. Elevation ranges from sea level to 800 feet (0 to 244 meters) with elevation extremes up to 1,600 feet (488 meters). The terrain is nearly level and gently sloping coastal plains and adjacent alluvial fans. Beneath the unconsolidated sediments are basalt, coral limestone, calcareous sand deposits, volcanic ash, coral sand, and fill. Average annual precipitation ranges from 10 to 40 inches (254 to 1,016 millimeters) with precipitation extremes up to 122 inches (3,099 millimeters) in select places on Oahu and Kauai (Giambelluca et al., 2013). Most of the rainfall occurs from November through March during kona storms that come in from the leeward side of the islands. Average annual temperatures range from 68 to 82 degrees F (20 to 28 degrees C) with little seasonal variation (Giambelluca et al., 2014). Dominant soils are Mollisols, Aridisols, Entisols, and Vertisols with an isohyperthermic soil temperature regime and aquic or aridic (torric) to ustic soil moisture regimes. Vegetation consists of forbs, grasses, and shrubs with some trees. Almost all the plant species typically encountered are introduced species that have become naturalized in Hawaii (USDA-NRCS, 2006).

Classification relationships

This ecological site occurs within Major Land Resource Area (MLRA) 163 - Alluvial Fans and Coastal Plains.

The Aha Moku System, which dates back to the 9th century and has been passed down through oral tradition and generational wisdom, effectively sustains Hawaii's natural ecosystems and environment (DLNR, 2024). This site-specific and resource-based approach balances land and ocean resources essential for fostering healthy, thriving communities. Grounded in Native Hawaiian generational knowledge, the Aha Moku System emphasizes community consultation to prioritize the health and welfare of Hawaii’s natural and cultural resources. It is rooted in the concept of 'ahupua'a, the traditional system of land and ocean management in Hawaii. For collaboration, this ecological framework encompasses the following mokus:

Kauai Moku Acres: Kona (4,621).

Oahu Moku Acres: ‘Ewa (6,899), Wai’anae (2,330), ko’olaupoko (722), Waialua (506), Kona (227), and Ko’olauloa (18).

Ecological site concept

This ecological site is naturalized grassland at low elevations on the leeward slopes of Oahu and Kauai (USDI-USGS, 2006). Much of the area is, or has been, in intensive agriculture or has been developed. Principal landowners are large private land companies, ranches, the State of Hawaii, and the Federal Government. It is accessed in the Pearl Harbor area and along parts of Route 93 on Oahu and along Route 50 north of Kekaha on Kauai.

The central concept of the South and West Aspect Isohyperthermic Naturalized Grassland is of well drained, shallow to very deep soils, in the Soil Orders of Mollisols or Aridisols, that formed in alluvium. Annual air temperatures and rainfall are associated with very warm (isohyperthermic), usually dry (aridic/torric or aridic/ustic intergrade) soil conditions (USDA-SCS, 1972). Elevations range from sea level (0 meters) to about 150 feet (46 meters) with elevation extremes up to 1,000 feet (305 meters). Because very little of the original native vegetation remains, the reference state of this ecological site consists of naturalized grassland vegetation. The dominant grass species is buffelgrass (Pennisetum ciliare). Common naturalized trees are kiawe (Prosopis pallida) and white leadtree or koa haole (Leucaena leucocephala).

The original native vegetation was dry forest or shrubland (Rock, 1913; Wagner et al., 1999). Common native species, based on the current environment and remnant occurrences, are alahe’e (Psydrax odorata), ohe makai (Reynoldsia sandwicensis), wili wili (Erythrina sandwicensis), naio (Myoporum sandwicense), Florida hopbush or aalii (Dodonaea viscosa), yellow ‘ilima (Sida fallax), and native grasses.

Associated sites

VX158X01X002	Isohyperthermic Torric Naturalized Grassland Kiawe/buffelgrass (Prosopis pallida/Pennisetum ciliare) The Isohyperthermic Torric Naturalized Grassland Ecological Site has similar climate and soils but does not have the hot, dry aspect of this ecological site. Plant species are very similar, but the Isohyperthermic Torric Naturalized Grassland will generally have higher production than this ecological site.
VX163X01X001	Shrink-Swell Clay Shrink-Swell Clay Ecological Site has a similar climate and aspect but very different soils. Shrink-Swell Clay has Vertisols that have greater water-holding capacity than this ecological site. Plant species are similar, but Shrink-Swell Clay should have higher production than this ecological site.
VX163X01X005	Aquic Coastal Wetland The Aquic Coastal Wetland Ecological Site has a similar climate to this ecological site, but it has wet, poorly and very poorly drained soils and, unless artificially drained, supports wetlands rather than dry rangeland.

VX158X01X002

Isohyperthermic Torric Naturalized Grassland Kiawe/buffelgrass (Prosopis pallida/Pennisetum ciliare)

The Isohyperthermic Torric Naturalized Grassland Ecological Site has similar climate and soils but does not have the hot, dry aspect of this ecological site. Plant species are very similar, but the Isohyperthermic Torric Naturalized Grassland will generally have higher production than this ecological site.

VX163X01X001

Shrink-Swell Clay

Shrink-Swell Clay Ecological Site has a similar climate and aspect but very different soils. Shrink-Swell Clay has Vertisols that have greater water-holding capacity than this ecological site. Plant species are similar, but Shrink-Swell Clay should have higher production than this ecological site.

VX163X01X005

Aquic Coastal Wetland

The Aquic Coastal Wetland Ecological Site has a similar climate to this ecological site, but it has wet, poorly and very poorly drained soils and, unless artificially drained, supports wetlands rather than dry rangeland.

Similar sites

VX163X01X003	East Aspect Isohyperthermic Naturalized Grassland The East Aspect Isohyperthermic Naturalized Grassland Ecological Site has a slightly cooler, moister climate than this ecological site, but its east-facing aspect creates still cooler, moister conditions that support plant species adapted to that environment.

VX163X01X003

East Aspect Isohyperthermic Naturalized Grassland

The East Aspect Isohyperthermic Naturalized Grassland Ecological Site has a slightly cooler, moister climate than this ecological site, but its east-facing aspect creates still cooler, moister conditions that support plant species adapted to that environment.

Table 1. Dominant plant species

Tree	(1) Prosopis pallida
Shrub	Not specified
Herbaceous	(1) Pennisetum ciliare

Legacy ID

R163XY004HI

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Physiographic features

This ecological site primarily occurs on alluvial fans at the base of shield volcanoes. Flooding typically does not occur in this ecological site. Some of the alluvium covers old coral limestone terraces, marine clay, or coral sand (USDA-SCS, 1972).

Table 2. Representative physiographic features

Landforms	(1) Shield volcano > Alluvial fan (2) Coastal plain > Flood plain (3) Coastal plain > Terrace
Runoff class	Very low to medium
Flooding frequency	None to occasional
Ponding frequency	None to rare
Elevation	150 ft
Slope	12%
Water table depth	72 in
Aspect	W, S, SW

Table 3. Representative physiographic features (actual ranges)

Runoff class	Not specified
Flooding frequency	Not specified
Ponding frequency	Not specified
Elevation	1,000 ft
Slope	35%
Water table depth	Not specified

Climatic features

Summary for this ecological site
Rainfall statistics were determined from University of Hawaii's Rainfall Atlas Raster Data (Giambelluca et al., 2013). Most of the precipitation falls from October through April. Representative (20th and 80th percentiles) values for annual average precipitation range from 21 to 25 inches (533 to 635 millimeters) while actual (10th and 90th percentiles) values for annual average precipitation range from 20 to 33 inches (508 to 838 millimeters). Extreme values range from 18 to 61 inches (457 to 1,550 millimeters). The mean annual precipitation is 24 inches (610 millimeters) and the median annual average precipitation is 22 inches (559 millimeters).

Temperature statistics were determined from University of Hawaii's Surface Temperature Raster Data (Giambelluca et al., 2014). Representative (20th and 80th percentiles) values for annual temperatures range from 77 to 81 degrees F (25 to 27 degrees C) while actual (10th and 90th percentiles) values for annual temperatures range from 77 to 82 degrees F (25 to 28 degrees C). Extreme values range from 73 to 82 degrees F (23 to 28 degrees C). The mean annual temperature is 79 degrees F (26 degrees C) and the median annual temperature is 77 degrees F (25 degrees C).

The data presented in the climate normals tables below are from the Western Region Climate Center (Western Regional Climate Center, 2020). The available climate station data are most representative of the low and moderate precipitation areas of this ecological site. I used these data because they provide a reasonable approximation of the University of Hawaii data presented above.

Conditions typically are very dry. Rainfall occurs as occasional light trade wind showers that drift over from the windward side of the island and as heavier rainfall during major winter storms. Major storms are important for soil moisture recharge, and the number of major storms is highly variable; drought can result from a winter with few or no storms. Due to the latitude, daylength varies little during the year, resulting in only about a 50 percent variation in solar energy input between June maximum to December minimum; this variation is somewhat less than that found in the continental United States. Due to the south and west aspects of this ecological site, it is exposed to the sun during the hottest parts of the day (Western Regional Climate Center, 2020).

General principles
Air temperature in the Hawaiian Islands is buffered by the surrounding ocean so that the range in temperature through the year is narrow. This creates "iso" - soil temperature regimes in which mean summer and winter temperatures differ by less than 6 degrees C (11 degrees F).

Hawaiian indigenous understanding recognized two seasons: Kau or Kauwela (dry season), and Ho`oilo (wet season). During Kau, the sun is directly overhead, days are long and warm, and the trade winds are stronger and more consistent; Kau started on the first new moon in May when the Pleiades set at sunrise (Handy et al., 1991). During Ho’oilo (wet season) the sun is declined toward the south, days are shorter, temperatures cooler and winds more variable and generally started with the first new moon in November. Ho’oilo is also the season when extensive low-pressure systems often approach the islands from the west, producing heavy rainstorms that primarily affect the leeward sides, but can envelope the entire island. (Malo, 1903; Handy et al., 1991; Sanderson, 1993). Differences in rainfall amounts between winter and summer are most marked in low elevation dry areas; wetter areas exhibit less seasonal variation in rainfall (Western Regional Climate Center, 2020).

The islands lie within the trade wind zone. Moisture is picked up from the ocean by trade winds to an altitude of about 6,000 feet (1,829 meters). As the trade winds from the northeast are forced up the islands’ mountains their moisture condenses, creating rain on the windward slopes; the leeward sides of the island receive little of this moisture. On West Maui, Kauai, Molokai, Oahu, and Lanai, where the mountains are all lower than 6,000 feet (1,829 meters), the highest rainfall amounts occur along or near the summits. The moist trade winds usually flow across these lower mountains and around the higher mountains (USDA-SCS, 1972; Western Regional Climate Center, 2020).

Besides the trade winds discussed above, other rainfall sources on the Hawaiian Islands include: a) "Naulu storms" (Leopold, 1949) caused by local convergence of sea breezes and trade winds to produce summertime cumulus clouds, resulting in infrequent, short-duration, high-intensity rainfall and afternoon shade over leeward dry areas; and b) fog drip, particularly important to areas with relatively low rainfall, that adds a significant amount of water to areas where clouds intersect mountains (Juvik and Nullet, 1993; Western Regional Climate Center, 2020).

The heaviest rains are brought by winter storms. The greatest amounts of storm rainfall do not always occur in areas with the highest average rainfall, and a storm may bring half of the mean annual rainfall to a dry area in one day.

Table 4. Representative climatic features

Frost-free period (characteristic range)	365 days
Freeze-free period (characteristic range)	365 days
Precipitation total (characteristic range)	21-25 in
Frost-free period (actual range)	365 days
Freeze-free period (actual range)	365 days
Precipitation total (actual range)	20-33 in
Frost-free period (average)	365 days
Freeze-free period (average)	365 days
Precipitation total (average)	24 in

Characteristic range

Actual range

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Figure 1. Monthly precipitation range

Characteristic range

Actual range

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Figure 2. Monthly minimum temperature range

Characteristic range

Actual range

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Figure 3. Monthly maximum temperature range

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Figure 4. Monthly average minimum and maximum temperature

Figure 5. Annual precipitation pattern

Figure 6. Annual average temperature pattern

Climate stations used

(1) BARKING SANDS [USW00022501], Kekaha, HI
(2) WAIMEA 947 [USC00519629], Kekaha, HI
(3) EWA KALAELOA AP [USW00022551], Kapolei, HI
(4) HONOLULU INTL AP [USW00022521], Honolulu, HI
(5) WAIKIKI 717.2 [USC00519397], Honolulu, HI
(6) KANEOHE BAY MCAS [USW00022519], MCBH Kaneohe Bay, HI
(7) CAMP ERDMAN 841.16 [USC00510305], Waialua, HI

Influencing water features

This ecological site is dissected by several intermittent and perennial streams and perennial lakes and ponds. Several soil components are overlapped by freshwater emergent wetlands. Many of the soil components occur adjacent to ocean water (USFWS, 2023).

Number of National Wetland Inventory (NWI) features overlapping ecological site: freshwater emergent wetlands (115), estuarine and marine wetland (102), riverine (96), freshwater pond (65), estuarine and marine deepwater (30), and freshwater forested/shrub wetland (19) (USFWS, 2023).

Number of National Hydrologic Dataset (NHD) features overlapping ecological Site: lake/pond (33), reservoir (31), swamp/marsh (5), stream/river (4), foreshore (2), sea/ocean (2), and canal/ditch (1) (USGS, 2019).

Soil features

The soil components associated with this ecological site are Kekaha, Mamala, Mokuleia, and Waipahu.

These are mineral soils that formed in alluvium from basic igneous rock and deposited over marine clay, coral limestone, consolidate calcareous sand, coral sand, or marine terraces. They have isohyperthermic (very warm) soil temperature regimes. Most of the soils have aridic soil moisture regimes (in normal years, dry for more than half of the growing season and moist for less than 90 consecutive days during the growing season) or are drier (torric or aridic) intergrades of ustic (in normal years, dry for more than 90 cumulative days but less than 180 days). All the soils are well drained. Surface horizons from 0 to 10 inches (0 to 254 millimeters) have pH values ranging from 6.3 to 7.6 while pH values from 10 to 20 inches (254 to 508 millimeters) range from 6.3 to 8.2 (USDA-SCS, 1972).

Mokuleia and Waipahu soils are classified as Mollisols. Many of the soils in very warm (mostly isohyperthermic, but sometimes isothermic), dry (torric, aridic, or ustic with aridic intergrade) areas of Hawaii are Mollisols or have mollic properties. Their key properties are a combination of a relatively thick, dark surface horizon (mollic epipedon) that does not become hard when dry, a dominance of calcium among the extractable cations, and a dominance of crystalline clay minerals of moderate or high cation-exchange capacity. These properties are conducive to plant growth. Although Mollisols usually form under grass in seasonally dry climates, they can form under a forest ecosystem. Mokuleia soils are shallow and have a clay surface texture. Waipahu soils are deep and have a silty clay texture; they have largely been used for urban development (USDA-SCS, 1972).

Keahu and Mamala soils are classified as Aridisols, which are soils with a light-colored surface horizon that has low organic matter content. They are moist for only short periods during the year. Kekaha soils are very deep and have surface horizons that are usually silty clay to clay texture. Mamala soils are shallow (typically about 19 inches or 48 centimeters deep) and have surface horizons with silty clay loam texture overlying coral limestone and consolidated calcareous sand (USDA-SCS, 1972).

Adjoining the soils described above are areas mapped as Miscellaneous Areas. By definition, they have little or no soil and support little or no vegetation. In the Five Islands Soil Survey upon which this ecological site is based, Miscellaneous Areas are extensive, and most and were mapped by low-intensity reconnaissance methods that provide less-detailed information than that presented for soil series and their phases. In many cases, however, Miscellaneous Areas in Maui, Molokai, Lanai, Oahu, and Kauai are moderately- to well-vegetated and/or contain plant and animal species of interest to conservationists. They are either extremely difficult to access or were not considered important enough at the time of this survey to warrant full expenditure of resources. They are described in the following paragraphs (USDA-SCS, 1972).

Coral Outcrop (CR) occurs on Oahu and Lanai. It consists of coral or cemented calcareous sand. Eighty to 90 percent is coral outcrop and 10 to 20 percent is a thin layer of friable, red soil material in cracks, crevices, and depressions. The soil material is similar to Mamala series. Much of this Miscellaneous Area is covered by urban development. Otherwise, it supports patches of grasses and kiawe (Prosopis pallida). Some areas on Oahu support dense stands of kiawe. It is not known if this is natural or due to crushing of stone or movement of fine materials by heavy equipment (USDA-SCS, 1972).

Table 5. Representative soil features

Parent material	(1) Alluvium – basalt
Surface texture	(1) Silty clay (2) Extremely stony silty clay loam (3) Cobbly silty clay loam (4) Clay
Family particle size	(1) Very-fine (2) Fine (3) Clayey over sandy or sandy-skeletal (4) Clayey
Drainage class	Well drained
Permeability class	Very slow to moderately slow
Depth to restrictive layer	72 in
Soil depth	72 in
Surface fragment cover <=3"	5%
Surface fragment cover >3"	9 – 10%
Available water capacity (0-40in)	2 – 5 in
Calcium carbonate equivalent (0-40in)	Not specified
Electrical conductivity (0-40in)	2 mmhos/cm
Sodium adsorption ratio (0-40in)	10
Soil reaction (1:1 water) (0-10in)	6.3 – 7.6
Subsurface fragment volume <=3" (0-40in)	2 – 10%
Subsurface fragment volume >3" (0-40in)	2 – 23%

Table 6. Representative soil features (actual values)

Drainage class	Not specified
Permeability class	Not specified
Depth to restrictive layer	19 – 72 in
Soil depth	19 – 72 in
Surface fragment cover <=3"	Not specified
Surface fragment cover >3"	Not specified
Available water capacity (0-40in)	Not specified
Calcium carbonate equivalent (0-40in)	99%
Electrical conductivity (0-40in)	Not specified
Sodium adsorption ratio (0-40in)	Not specified
Soil reaction (1:1 water) (0-10in)	Not specified
Subsurface fragment volume <=3" (0-40in)	Not specified
Subsurface fragment volume >3" (0-40in)	Not specified

Ecological dynamics

The information in this ecological site description (ESD), including the state-and-transition model (STM), was developed using archaeological and historical data, professional experience, and scientific studies. The information is representative of a complex set of plant communities. Not all scenarios or plants are included. Key indicator plants, animals, and ecological processes are described to inform land management decisions.

Natural Disturbances

There have been no lava flows or volcanic ash flows on this ecological site that are recent enough to have affected the current vegetation and soils (USDA-SCS, 1972). It is possible that strong storms may sometimes cause minor windthrow of trees. Wildfires started by lightning rarely may affect this ecological site (Abrahamson, 2013).

Human Disturbances

Human-related disturbances have been more important than natural disturbances in this ecological site since the arrival of Polynesians and, later, Europeans. This is reflected in the state-and-transition model diagram.

Humans arrived in the Hawaiian Islands 1,200 to 1,500 years ago. Their population gradually increased so that by 1,600 A.D. at least 80 percent of all the lands in Hawaii below about 1,500 feet (roughly 457 meters) in elevation had been extensively altered by humans (Kirch, 1982); some pollen core data suggest that up to 100 percent of lowlands may have been altered (Athens, 1997). By the time of European contact late in the 18th century, the Polynesians had developed high population densities and placed large areas under intensive agriculture (Cuddihy and Stone, 1990).

Prehistoric native lowland forest disturbance can be attributed to clearing for agriculture by hand or by fire, introduction of new plants, animals, possibly plant diseases, and wood harvesting. The introduced Pacific rat would have eaten bird eggs, invertebrates, and the seeds of native plants (Athens, 1997).

Approximately 20 percent (3,711 acres) of this 18,001-acre ecological site overlaps with the Lincoln et al., (2023) modeled Marginal Colluvium agroecological systems.

These Marginal Colluvial systems were implemented on colluvial deposits on steeper and more arid ground where additional cultivation efforts were not worth the investments of time and infrastructure. This cultivation system would include, Portia tree or milo (Thespesia populnea), kou (Cordia subcordata), and Alexandrian laurel or kamani (Calophyllum inophyllum), with opportunistic plantings of drought-tolerant crops such as sweetpotato or uala (Ipomoea batatas) and bottle gourd or ipu (Lagenaria siceraria) (Lincoln et al., 2023).

After the arrival of Europeans, documentary evidence attests to accelerated and extensive deforestation, erosion, siltation, and changes in local weather patterns (Kirch, 1983) due to more intensive land use, modern tools, and introduction of more plant, animal, and microbe species. Introduced kiawe trees (Prosopis pallida) are widespread in this ecological site.

The Polynesians introduced dogs, Pacific rats, and small pigs to the islands. After European discovery, cattle, sheep, horses, goats, and larger European pigs were introduced in the final decades of the 18th century. These animals ranged free on the islands, becoming very numerous and destructive by the early decades of the 19th century. Additionally, packs of feral dogs had become established, as confirmed by reports of their depredations on sheep. By 1851, records reported severe overstocking of pastures, lack of fences, and large numbers of feral livestock (Henke, 1929).

Through the 20th and into the 21st centuries, increases in human populations with attendant land development, as well as accelerated introduction of non-native mammals (including deer), birds, reptiles, amphibians, invertebrates, plants, and microorganisms, have brought about dramatic changes to wild ecosystems in Hawaii.

State and transition model

Custom diagram

Standard diagram

Figure 7. State-and-transition model diagram for the South and West Aspect Isohyperthermic Naturalized Grassland (R163XY004HI).

More interactive model formats are also available. View Interactive Models

More interactive model formats are also available. View Interactive Models
Click on state and transition labels to scroll to the respective text

Ecosystem states

1. Reference State

2. Kiawe-Invaded, >25% Cover

3. Native Savanna State

T1A	-	The Reference State (1) transitions to the Kiawe-Invaded State (2) with lack of brush management practices or absence of fire.
R1A	-	The Reference State (1) can be restored to a facsimile of the Native Savanna State (3). The site must be protected from domestic and feral ungulates and fire. Buffelgrass and other non-native vegetation must be killed, followed by plantings of native trees, shrubs, and vines. Supplemental irrigation would be necessary in the early stages of restoration.
R2A	-	The Kiawe-Invaded State (2) can be restored to the Reference State (1) by applying brush management. Fire will kill kiawe, but prescribed burning is typically not done in Hawaii due to the level of risk.
T3A	-	The Native Savanna State (3) transitions to the Reference State (1) when cleared by fire, long-term ungulate disturbance, or mechanical means. Desired forage species are then re-established.

State 1 submodel, plant communities

1.1. Buffelgrass With <25% Kiawe Cover

1.2. Buffelgrass – Pitted Beardgrass With <25% Kiawe Cover

1.3. Sweet Acacia (Klu)/Bermudagrass/Lantana

1.1A	-	Buffelgrass cover and vigor are reduced by continuous grazing, causing it to decrease and be partially replaced by less desirable forages.
1.2B	-	Community phase 1.2 can change to phase 1.1 by application of a prescribed grazing program that allows buffelgrass to reassume dominance. Weed control may be necessary if taller weedy forbs and/or shrubs are abundant.
1.2A	-	Community phase 1.2 changes to phase 1.3 with long-term or heavy continuous grazing. Species composition changes to dominance by shortgrasses, weedy forbs, and shrubs. Bare ground increases markedly.
1.3A	-	Community phase 1.3 can change to phase 1.2 by application of a prescribed grazing program that allows buffelgrass to reassume dominance. Weed control may be necessary.

State 2 submodel, plant communities

2.1. Buffelgrass With >25% Kiawe Cover

State 3 submodel, plant communities

3.1. Wili Wili/Native Caper (Maiapilo)

State 1
Reference State

The Reference State (1) consists of three community phases dominated by introduced grasses and less than 25 percent canopy cover of introduced trees. With lack of brush control or absence of wildfire, this state (1) will transition to the Kiawe-Invaded State (2), in which production and cover of buffelgrass and other forages is reduced. Accumulation of fine fuels under light or no grazing pressure increases the risk of fire. This can produce an open grassland with little tree overstory but presents a fire threat to developed areas nearby and likelihood of eroded soil entering the nearby ocean.

Community 1.1
Buffelgrass With <25% Kiawe Cover

Buffelgrass (Pennisetum ciliare) is the dominant forage species present. Kiawe (Prosopis pallida) and white leadtree or koa haole (Leucaena leucocephala) may be present. Kiawe is a potentially tall tree; its pods have some forage value. If present at canopy cover greater than 25 percent, it can reduce production of grasses and forbs. Koa haole is a small, leguminous tree that is browsed by livestock. Under continuous or heavy grazing, this phase will change to phase 1.2 Buffelgrass-Pitted Beardgrass With <25% Kiawe Cover. With continuous heavy grazing, particularly by cattle, buffelgrass will decrease. Koa haole will decrease under heavy browsing pressure. Increasers include beardgrass (Bothriochloa spp.), windmill grass (annual fingergrasses) (Chloris spp.), Bermudagrass (Cynodon dactylon), and weedy forbs. With severe deterioration, shrubby species such as lantana (Lantana camara) and American black nightshade or apple of Sodom (Solanum americanum) increase.

Dominant plant species

kiawe (Prosopis pallida), tree
buffelgrass (Pennisetum ciliare), grass

Community 1.2
Buffelgrass – Pitted Beardgrass With <25% Kiawe Cover

This community phase consists of lower-value grass species that become abundant upon continuous heavy grazing of buffelgrass. Further overgrazing exacerbates this process, causing a community change to phase 1.3. Kiawe (Prosopis pallida) canopy cover is less than 25 percent. Pitted beardgrass (Bothriochloa pertusa) and swollen fingergrass (Chloris barbata) have both increased in cover and production. Buffelgrass (Pennisetum ciliare) abundance is much reduced. Koa haole is much reduced compared with phase 1.1. Unpalatable species such as uhaloa (Waltheria indica), sensitive partridge pea or Japanese tea (Chamaecrista nictitans), and golden crownbeard (Verbesina encelioides) have increased.

Dominant plant species

kiawe (Prosopis pallida), tree
buffelgrass (Pennisetum ciliare), grass
pitted beardgrass (Bothriochloa pertusa), grass

Community 1.3
Sweet Acacia (Klu)/Bermudagrass/Lantana

This community phase consists mostly of grass species that are highly tolerant of grazing, particularly Bermudagrass (Cynodon dactylon), along with increased amounts of unpalatable shrubs, forbs, and subshrubs. White leadtree or koa haole (Leucaena leucocephala) is gone or is browsed down to stumps. Buffelgrass (Pennisetum ciliare) is present but reduced in abundance. Bare ground is extensive, so soil erosion by wind and water can be excessive. Kiawe (Prosopis pallida) canopy cover is less than 25 percent. The most abundant grass species is Bermudagrass (Cynodon dactylon). Sweet acacia or klu (Acacia farnesiana) and lantana (Lantana camara) are common, unpalatable shrubs. Some native species including Florida hopbush or aalii (Dodonaea viscosa), yellow ‘ilima (Sida cordifolia), and uhaloa (Waltheria indica) typically are present.

Dominant plant species

sweet acacia (Acacia farnesiana), tree
lantana (Lantana camara), shrub
Bermudagrass (Cynodon dactylon), grass

Pathway 1.1A
Community 1.1 to 1.2

Buffelgrass cover and vigor are reduced by continuous grazing, causing it to decrease and be partially replaced by less desirable forages.

Pathway 1.2B
Community 1.2 to 1.1

Community phase 1.2 can change to phase 1.1 by application of a prescribed grazing program that allows buffelgrass to reassume dominance. Weed control may be necessary if taller weedy forbs and/or shrubs are abundant.

Pathway 1.2A
Community 1.2 to 1.3

Community phase 1.2 changes to phase 1.3 with long-term or heavy continuous grazing. Species composition changes to dominance by shortgrasses, weedy forbs, and shrubs. Bare ground increases markedly.

Pathway 1.3A
Community 1.3 to 1.2

Community phase 1.3 can change to phase 1.2 by application of a prescribed grazing program that allows buffelgrass to reassume dominance. Weed control may be necessary.

State 2
Kiawe-Invaded, >25% Cover

The Kiawe-Invaded State (2) consists of one community phase. It occurs when brush management has not been practiced or if wildfire has not occurred for a long time, allowing kiawe to increase in density and stature to a level at which understory production is significantly reduced.

Community 2.1
Buffelgrass With >25% Kiawe Cover

The kiawe canopy cover is 25 percent or higher. The understory consists of remnant buffelgrass and other grasses. This plant community is poor for livestock grazing due to reduced forage amounts beneath the dense tree canopy. Bare ground has increased.

Dominant plant species

kiawe (Prosopis pallida), tree
buffelgrass (Pennisetum ciliare), grass

State 3
Native Savanna State

The Native Savanna State (3) consists of one community phase. Intact examples of this community no longer exist. This historical description is compiled from field observations of remnant vegetation, isolated plants on disturbed sites, and historical accounts of the islands before human influences disturbed these native plant communities.

Community 3.1
Wili Wili/Native Caper (Maiapilo)

This historical community phase is an open canopy of low to medium height (15 to 25 feet; 4.5 to 8 meters) trees, a shrub understory, and a ground layer of vines, herbs, and grasses. The species present would be typical of other low elevation dry Hawaiian sites. Common tree species are those that are found in Hawaiian dry forests, with an emphasis on species that are adapted for the lower elevations and warmest, driest end of the spectrum (Rock, 1913; Wagner et al., 1999). Among these are ohe makai (Reynoldsia sandwicensis), wili wili (Erythrina sandwicensis), and lama (Diospyros sandwicensis). Among the common native shrubs would be alaweo or aheahea (Chenopodium oahuense), Florida hopbush or aalii (Dodonaea viscosa), native caper or maiapilo (Capparis sandwichiana), and Oahu riverhemp or ohai (Sesbania tomentosa). Common forbs would be smooth pricklypoppy or pua kala (Argemone glauca) and nehe (Lipochaeta spp.). Some common grass species would be kawelu (Eragrostis variabilis), tanglehead or pili (Heteropogon contortus), Kona panic grass or kakonakona (Panicum konaense) Faurie’s panicgrass (P. fauriei), torrid panicgrass (P. torridum). Common vines would be kauna’oa (Cuscuta sandwichiana), oval-leaf clustervine or pauohiiaka (Jacquemontia ovalifolia ssp. sandwicensis), and paha or kupala (Sicyos pachycarpus) (Rock, 1913; Wagner et al., 1999).

Dominant plant species

wili wili (Erythrina sandwicensis), tree
native caper (Capparis sandwichiana), shrub

Transition T1A
State 1 to 2

The Reference State (1) transitions to the Kiawe-Invaded State (2) with lack of brush management practices or absence of fire.

Restoration pathway R1A
State 1 to 3

The Reference State (1) can be restored to a facsimile of the Native Savanna State (3). The site must be protected from domestic and feral ungulates and fire. Buffelgrass and other non-native vegetation must be killed, followed by plantings of native trees, shrubs, and vines. Supplemental irrigation would be necessary in the early stages of restoration.

Restoration pathway R2A
State 2 to 1

The Kiawe-Invaded State (2) can be restored to the Reference State (1) by applying brush management. Fire will kill kiawe, but prescribed burning is typically not done in Hawaii due to the level of risk.

Transition T3A
State 3 to 1

The Native Savanna State (3) transitions to the Reference State (1) when cleared by fire, long-term ungulate disturbance, or mechanical means. Desired forage species are then re-established.

Additional community tables

Supporting information

Other references

References for R163XY001HI Shrink-Swell Clay

Abrahamson, I.L. (2013). Fire regimes in Hawai’ian plant communities. Fire Effects
Information System [https://www.fs.usda.gov/database/feis/fire_regimes/Hawaii/all.html].

Athens, J.S. (1997). Prehistoric environmental and landscape change. In Kirch, P.V. & T.L. Hunt (Eds.), Hawai’ian native lowland vegetation in the Pacific Islands (Pgs. 248 -270). Yale University Press. [https://www.pelagicos.net/BIOL3010/readings/Athens_1997.pdf].

Cuddihy, L.W., & C.P. Stone. (1990). Alteration of native Hawai’ian vegetation: Effects of humans, their activities and introductions. University of Hawaii Cooperative National Park Resources Study Unit.

Department of Land and Natural Resources (2024). Hawai’i State Aha Moku. [https://dlnr.hawaii.gov/ahamoku/councils/].

Giambelluca, T.W., Q. Chen, A.G. Frazier, J.P. Price, Y.L. Chen, P.-S. Chu, J.K. Eischeid, & D.M. Delparte. (2013): Online rainfall atlas of Hawai’i. Bull. Amer. Meteor. Soc. 94, 313-316, DOI: [https://doi.org/10.1175/BAMS-D-11-00228.1].

Giambelluca, T.W., X. Shuai, M.L. Barnes, R.J. Alliss, R.J. Longman, T. Miura, Q. Chen, A.G. Frazier, R.G. Mudd, L. Cuo, & A.D. Businger. (2014). Evapotranspiration of Hawai’i. Final report submitted to the U.S. Army Corps of Engineers - Honolulu District, and the Commission on Water Resource Management, State of Hawai’i. [https://www.hawaii.edu/climate-data-portal/evapotranspiration-atlas/].

Handy, E.S.C., E.G. Handy, & Pukui, M.K. (First Edition 1972, Revised Edition 1991). Native planters in old Hawai’i: Their life, lore, and environment. Bishop Museum Press.

Henke, L.A. (1929). A survey of livestock in Hawai’i. Research Publication No. 5. University of Hawai’i, Honolulu. [https://www.ctahr.hawaii.edu/oc/freepubs/pdf/RP-5.pdf].

Juvik, J.O., & Nullett, D. (1993). A climate transect through tropical montane rain forests in Hawai’i. Department of Geography, University of Hawai’i at Hilo, Hilo Hawai’i. Journal of Applied Meteorology. Volume 33.

Kirch, P.V. (1982). The impact of the prehistoric Polynesians in the Hawai’ian ecosystem. Pacific Science 36 (1):1-14.

Kirch, P.V. (1983). Introduction. In Archaeological investigations of the Mudlane-Waimea-Kawaihae Road Corridor, Island of Hawai’i: An Interdisciplinary Study of an Environmental Transect. Clark, J.T. and Kirch, P.V., eds. Dept. of Anthropology, Bernice Pauahi Bishop Museum, Report 83-1, Honolulu, HI.

Leopold, L.B. (1949). The interaction of trade wind and sea breeze, Hawai’i. Journal of Meteorology 6: 312-320.

Lincoln, N.K, T.P. Haensel, & Lee, T.M. (2023). Modeling Hawai’ian agroecology: Depicting traditional adaptation to the world’s most diverse environment. Frontiers in Sustainable Food Systems. Climate-Smart Food Systems. Volume 7 – 2023.
[https://doi.org/10.3389/fsufs.2023.1116929].

Malo, D. (1903). Hawaiian antiquities. N.B. Emerson (trans.). Bishop Museum Special Publication 2. Honolulu.

Rock, J.F. (1st edition 1913, reprinted 1974). The Indigenous trees of the Hawai’ian Islands. C. E. Tuttle Company, Rutland, V.T. & Tokyo, Japan.

Sanderson, M. (ed.). (1993). Prevailing trade winds, weather and climate in Hawai’i. University of Hawai’i Press. Honolulu.

U.S. Department of Agriculture, Natural Resources Conservation Service. (2006). Land resource regions and major land resource areas of the United States, the Caribbean, and the Pacific Basin. United States Department of Agriculture, Agriculture Handbook 296. [https://www.nrcs.usda.gov/sites/default/files/2022-10/AgHandbook296_text_low-res.pdf].

U.S. Department of Agriculture, Soil Survey Conservation Service. (1972). Soil survey of Islands of Kauai, Oahu, Maui, Molokai, and Lanai, State of Hawai’i. Foote D.E., Hill E.L., Nakamura S., & F. Stephens, in cooperation with The University of Hawai’i Agricultural Experiment Station.

U. S. Department of Interior, Fish & Wildlife Service. (2023). Download seamless wetlands data by state. National Wetlands Inventory website. U.S. Department of the Interior, Fish and Wildlife Service, Washington, D.C. Accessed April 24, 2024. [https://www.fws.gov/program/national-wetlands-inventory/download-state-wetlands-data].

U.S. Department of Interior, Geological Survey. (2006). A Gap analysis of Hawai’i: February 2006 final report. National gap analysis program. [https://catalog.lib.uchicago.edu/vufind/Record/6329681/Details].

U.S. Department of Interior, Geological Survey. (2019). National Hydrography Dataset (NHD) – USGS national map downloadable data collection: USGS – National Geospatial Technical Operations Center (NGTOC). [https://www.usgs.gov/national-hydrography/access-national-hydrography-products].

Wagner, W.L., D.R. Herbst, & S.H. Sohmer. (1999). Manual of the flowering plants of Hawai’i, Revised Edition. Bishop Museum Press, Honolulu.

Western Regional Climate Center, (2020). Climate of Hawai’i. Available: [https://wrcc.dri.edu/Climate/narrative_hi.php].

DEFINITIONS
These definitions have been greatly simplified for brevity and do not cover every aspect of each topic.

Alluvial: Materials or processes associated with transportation and/or deposition by running water.

Aquic soil moisture regime: A regime in which the soil is free of dissolved oxygen because it is saturated by water. This regime typically exists in bogs or swamps.

Aridic soil moisture regime: A regime in which defined parts of the soil are, in normal years, dry for more than half of the growing season and moist for less than 90 consecutive days during the growing season. In Hawaii it is associated with hot, dry areas with plants such as kiawe, wiliwili, and buffelgrass. The terms aridic and torric are basically the same.

Available water capacity: The amount of soil water available to plants to the depth of the first root-restricting layer.

CaCO3 equivalent: The amount of free lime in a soil. Free lime exists as solid material and typically occurs in regions with a dry climate.
Canopy cover: The percentage of ground covered by the vertical projection downward of the outermost perimeter of the spread of plant foliage. Small openings within the canopy are included.

Community pathway: A description of the causes of shifts between community phases. A community pathway is reversible and is attributable to succession, natural disturbances, short-term climatic variation, and facilitating practices, such as grazing management.

Community phase: A unique assemblage of plants and associated dynamic soil properties within a state.

Dominant species: Plant species or species groups that exert considerable influence upon a community due to size, abundance, or cover.

Drainage class: The frequency, duration, and depth of a water table in a soil. There are seven drainage classes, ranging from “excessively drained” (soils with very rare or very deep water tables) to “well drained” (soils that provide ample water for plant growth but are not so wet as to inhibit root growth) to “very poorly drained” (soils with a water table at or near the surface during much of the growing season that inhibits growth of most plants).

Electrical conductivity (EC): A measure of the salinity of a soil. The standard unit is deciSiemens per meter (dS/m), which is numerically equivalent to millimhos per centimeter (mmhos/cm). An EC greater than about 4 dS/m indicates a salinity level that is unfavorable to growth of most plants.

Isohyperthermic soil temperature regime: A regime in which mean annual soil temperature is 72 degrees F (22 degrees C) or higher and mean summer and mean winter soil temperatures differ by less than 11 degrees F (6 degrees C) at a specified depth.

Isothermic soil temperature regime: A regime in which mean annual soil temperature is 59 degrees F (15 degrees C) or higher but lower than 72 degrees F (22 degrees C) and mean summer and mean winter soil temperatures differ by less than 11 degrees F (6 degrees C) at a specified depth.

Major Land Resource Area (MLRA): A geographic area defined by NRCS that is characterized by a particular pattern of soils, climate, water resources, and land uses. The island of Hawaii contains nine MLRAs, some of which also occur on other islands in the state.

Medial: A “soil texture modifier” for volcanic ash soils having a water content at the crop wilting point of 30 to 100 percent; a soil that holds an amount of water intermediate to “hydrous” or “ashy” soils.

Mollisols: Soils with relatively thick, dark surface horizons, high cation-exchange capacity, high calcium content, that do not become hard or very hard when dry. Mollisols are conducive to plant growth. They characteristically form under grass in climates that are seasonally dry but can form under forests.

Naturalized plant community: A community dominated by adapted, introduced species. It is a relatively stable community resulting from secondary succession after disturbance. Most grasslands in Hawaii are in this category.

Parent material: Unconsolidated and chemically weathered material from which a soil is developed.

pH: The numerical expression of the relative acidity or alkalinity of a soil sample. A pH of 7 is neutral; a pH below 7 is acidic and a pH above 7 is basic.

Reference community phase: The phase exhibiting the characteristics of the reference state and containing the full complement of plant species that historically occupied the site. It is the community phase used to classify an ecological site.

Reference state: A state that describes the ecological potential and natural or historical range of variability of an ecological site.

Restoration pathway: A term describing the environmental conditions and practices that are required to recover a state that has undergone a transition.

Sodium adsorption ratio (SAR): A measure of the amount of dissolved sodium relative to calcium and magnesium in the soil water. SAR values higher than 13 create soil conditions unfavorable to most plants.

Soil moisture regime: A term referring to the presence or absence either of ground water or of water held at a tension of less than 1,500 kPa (the crop wilting point) in the soil or in specific horizons during periods of the year.

Soil temperature regime: A defined class based on mean annual soil temperature and on differences between summer and winter temperatures at a specified depth.

Soil reaction: Numerical expression in pH units of the relative acidity or alkalinity or a soil.

State: One or more community phases and their soil properties that interact with the abiotic and biotic environment to produce persistent functional and structural attributes associated with a characteristic range of variability.

State-and-transition model: A method used to display information about relationships between vegetation, soil, animals, hydrology, disturbances, and management actions on an ecological site.

Torric soil moisture regime: See Aridic soil moisture regime.

Transition: A term describing the biotic or abiotic variables or events that contribute to loss of state resilience and result in shifts between states.

Ustic soil moisture regime: A regime in which moisture is limited but present at a time when conditions are suitable for plant growth. In Hawaii it usually is associated with dry forests and subalpine shrublands.

Contributors

John Proctor
Carolyn Auweloa
Kendra Mosely
Amy Koch
Ann Tan
Jennifer Fedenko
Daniel Bowman
Sarah Quistberg
David Clausnitzer PhD

Approval

Kendra Moseley, 5/08/2025

Acknowledgments

Assistance, advice, review, and/or insights:

Randy Bartlett, Puu Kukui Watershed Preserve
Alison Cohan, The Nature Conservancy
Michael Constantinides, NRCS-PIA
Gordon Cran, Kapapala Ranch
Diana Crow, Ulupalakua Ranch
Lance DeSilva, Hawaii DLNR
Kerri Fay, Waikamoi Preserve, The Nature Conservancy
Alex Franco, Kaupo Ranch
Ranae Ganske-Cerizo, NRCS
Carl Hashimoto, NRCS
Bob Hobdy, consultant
Wallace Jennings, NRCS
Mike Kolman, NRCS
Jennifer Higashino, NRCS
Matthew Cocking, NRCS
Mel Johansen, The Nature Conservancy
Jordan Jokiel, Haleakala Ranch
David Leonard, volunteer
Penny Levin
Reese Libby, GIS - NRCS
Hannah Lutgen, Maui SWCD
Joseph May, NRCS
Scott Meidel, Haleakala Ranch
Anna Palomino, Hoolawa Farms Inc.
Jon Price, USGS
Tamara Sherrill, USFWS, Maui Nui Botanical Garden
Amber Starr, Hana Ranch
Kahana Stone, NRCS
Mark Vaught, Water Resources, Alexander & Baldwin
Jacqueline Vega, NRCS
Rich von Wellsheim, Whispering Bamboos, Kipahulu

Rangeland health reference sheet

Interpreting Indicators of Rangeland Health is a qualitative assessment protocol used to determine ecosystem condition based on benchmark characteristics described in the Reference Sheet. A suite of 17 (or more) indicators are typically considered in an assessment. The ecological site(s) representative of an assessment location must be known prior to applying the protocol and must be verified based on soils and climate. Current plant community cannot be used to identify the ecological site.

Author(s)/participant(s)
Contact for lead author
Date	05/11/2025
Approved by	Kendra Moseley
Approval date
Composition (Indicators 10 and 12) based on	Annual Production