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Ecological site VX164X01X401

Poorly Drained Bog

Last updated: 5/08/2025
Accessed: 09/23/2026

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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): 164X–Humid and Very Humid Steep and Very Steep Mountain Slopes

This MLRA occurs in the State of Hawaii on the islands of Hawaii, Maui, Molokai, Oahu, and Kauai. It consists primarily of deeply dissected mountainous areas. Elevation ranges from sea level to 7000 feet (0 to 2100 meters). Topography is mostly steep, with ridges, gulches, and canyons, as well as areas of plateau. Underlying geology is fractured, basic, igneous rock (mostly basalt) that is slightly to highly weathered. Over this are found deposits of local volcanic ash, tropospheric dust from Asia, and/or organic deposits. Climate is mostly wet tropical. Average annual precipitation typically ranges from 75 to 250 inches (1875 to 6250 millimeters), with extremes of 30 to 450 inches (750 to 11,250 millimeters). Rainfall is well distributed throughout the year with and enhanced rainy season from November through April. Fog drip can add significant amounts of water to the soil. Average annual temperatures range from 53 to 75 degrees F (12 to 24 degrees C), with very little seasonal variation. Soils are mostly Inceptisols, Andisols, and Histosols with isothermic or isomesic soil temperature regimes. Native vegetation consists of moderate stature rainforests, dwarf forests, and stands of uluhe with emergent shrubs and trees.

Classification relationships

This ecological site occurs within Major Land Resource Area (MLRA) 164 - Humid and Very Humid Steep and Very Steep Mountain Slopes.

Ecological site concept

This ecological site is an open-canopied bog on the very wet, high-elevation plateau on Mount Waialeale on the island of Kauai. It is within a State Forest Reserve. No public roads provide direct access to it. Two much smaller examples at lower elevation are mapped on the same soil series but have a different array of plant species.

The central concept of the Poorly Drained Bog is of poorly drained, deep soils formed in residuum weathered from basic igneous rock. Surface horizons (to about 23 inches deep) show signs of frequent but not permanent water saturation. Deeper horizons to 32 inches deep are gleyed, meaning that they are continuously saturated and anaerobic. Saturation is caused by water perching above the C horizon. Vegetation is an open bog dominated by native sedges and grasses. Interspersed in this are low stature shrubs, forbs, and tree species. Due to the gently undulating terrain, water table depths vary and some small areas are shallowly ponded.

Associated sites

VX164X01X005	Somewhat Poorly Drained Organic Surface Forest Both ecological sites occur on Kauai. The Poorly Drained Bog adjoins the extreme eastern boundary of the Somewhat Poorly Drained Organic Surface Forest. The ecological sites share a similar climate and elevation, but the Poorly Drained Bog lacks an organic horizon. The Poorly Drained Bog has vegetation that is shorter and more open than that of the Somewhat Poorly Drained Organic Surface Forest.
VX164X01X003	Very Poorly Drained Terric Forest Both ecological sites occur on Kauai, but the Very Poorly Drained Terric Forest also occurs in three small locations on Oahu. The Poorly Drained Bog adjoins the extreme eastern boundary of the Very Poorly Drained Terric Forest, and there probably are inclusions of it within the Somewhat Poorly Drained Forest. The ecological sites share a similar climate and elevation, but the Poorly Drained Bog lacks an organic horizon. It has vegetation that is shorter and more open than the Very Poorly Drained Terric Forest.

VX164X01X005

Somewhat Poorly Drained Organic Surface Forest

Both ecological sites occur on Kauai. The Poorly Drained Bog adjoins the extreme eastern boundary of the Somewhat Poorly Drained Organic Surface Forest. The ecological sites share a similar climate and elevation, but the Poorly Drained Bog lacks an organic horizon. The Poorly Drained Bog has vegetation that is shorter and more open than that of the Somewhat Poorly Drained Organic Surface Forest.

VX164X01X003

Very Poorly Drained Terric Forest

Both ecological sites occur on Kauai, but the Very Poorly Drained Terric Forest also occurs in three small locations on Oahu. The Poorly Drained Bog adjoins the extreme eastern boundary of the Very Poorly Drained Terric Forest, and there probably are inclusions of it within the Somewhat Poorly Drained Forest. The ecological sites share a similar climate and elevation, but the Poorly Drained Bog lacks an organic horizon. It has vegetation that is shorter and more open than the Very Poorly Drained Terric Forest.

Table 1. Dominant plant species

Tree	(1) Metrosideros polymorpha
Shrub	(1) Dubautia waialealae
Herbaceous	(1) Rhynchospora chinensis ssp. spiciformis

Legacy ID

R164XY401HI

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Physiographic features

This ecological site occurs on weathered basaltic lava flows.

Table 2. Representative physiographic features

Landforms	(1) Shield volcano > Plateau > Lava flow unit
Runoff class	High
Flooding frequency	None
Ponding frequency	None
Elevation	2200 – 5150 ft
Slope	8 – 30 %
Water table depth	0 – 32 in
Aspect	Aspect is not a significant factor

Table 3. Representative physiographic features (actual ranges)

Runoff class	Not specified
Flooding frequency	Not specified
Ponding frequency	Not specified
Elevation	2200 – 5199 ft
Slope	0 %
Water table depth	0 in

Climatic features

Climate Narrative

Summary for this ecological site
Average annual precipitation ranges from 160 inches (4,064 millimeters) to 450 inches (11,430 millimeters). Rainfall occurs throughout the year, with the heaviest precipitation occurring from October through April. Landscapes are shrouded in fog or overcast during much of the day throughout the year, which reduces evapotranspiration and adds additional moisture from condensation of fog on vegetation. Mean annual temperature is about 64 degrees F (17 degrees C). Frost free and freeze free periods are 365 days per year. Kauai is the northernmost of the larger Hawaiian Islands, exposing the island to more mid-latitude frontal weather systems than the other islands.

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).

The islands lie within the trade wind zone. Significant amounts of moisture are picked up from the ocean by trade winds up to an altitude of more than about 6000 feet (1850 meters). As the trade winds from the northeast are forced up the mountains of the islands their moisture condenses, creating rain on the windward slopes; the leeward sides of the island receive little of this moisture.

Two seasons can be defined during the year: a seven-month winter season from October through April and a five-month summer season from May through September. Summer has warmer temperatures, steadier and stronger trade winds, few widespread rainstorms, and generally lower average monthly rainfall than winter. Differences in rainfall amounts between winter and summer are most marked in low elevation dry areas; wetter areas exhibit less seasonal variation in rainfall.

On the windward sides of the island, cool, moist air at higher elevations descends toward the ocean where it meets the trade winds; this process brings rainfall, often at night, to lower elevation areas.

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. These major storms occur most frequently between October and March.

Table 4 Representative climatic features

Frost-free period (characteristic range)
Freeze-free period (characteristic range)
Precipitation total (characteristic range)	160-450 in
Frost-free period (average)	370 days
Freeze-free period (average)	370 days
Precipitation total (average)	310 in

Soil features

This ecological site exists on Koolau series soils. This series consists of deep soils that formed in a poorly drained area from residuum of basaltic lava. The surface horizon consists of massive silty clay. Most roots occur within the top 7 inches (17.5 centimeters) of soil; roots decline rapidly in abundance with depth and appear to be absent below about 23 inches (58 centimeters). Horizons between about 23 and 32 inches (58 to 80 centimeters) are gleyed, meaning they are permanently saturated with water and anaerobic. The soils are poorly drained and are sometimes saturated to the surface. The soil moisture regime is aquic (defined as a mostly reducing soil moisture regime nearly free of dissolved oxygen due to saturation by groundwater or its capillary fringe and occurring at periods when the soil temperature at 50 cm below the surface is >5°C.). The soil temperature regime is isothermic but in the cooler extreme of that regime. Soil reaction is extremely acid (pH 4.1 to 4.4) in the upper 11 inches (27.5 centimeters) and extremely acid to very strongly acid (pH 4.4 to 4.7) in the subsurface horizons.

Table 5. Representative soil features

Parent material	(1) Residuum – igneous rock
Surface texture	(1) Silty clay
Family particle size	(1) Medial
Drainage class	Poorly drained
Permeability class	Very slow
Depth to restrictive layer	72 in
Soil depth	72 in
Surface fragment cover <=3"	Not specified
Surface fragment cover >3"	Not specified
Available water capacity (0-40in)	5 in
Calcium carbonate equivalent (0-40in)	Not specified
Electrical conductivity (0-40in)	Not specified
Sodium adsorption ratio (0-40in)	Not specified
Soil reaction (1:1 water) (0-40in)	3.6 – 5
Subsurface fragment volume <=3" (0-40in)	3 %
Subsurface fragment volume >3" (0-40in)	2 %

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

Possible natural disturbances are hurricanes and, in some locations, landslides.

Human Disturbances

This ecological site is nearly inaccessible on foot. However, ancient Hawaiians built a heiau (temple or sacred site) and altered a pool here. There are no roads, and much of the site is surrounded by fences to exclude introduced ungulates.

Humans arrived in the Hawaiian Islands 1200 to 1500 years ago. Their population gradually increased so that by 1600 AD at least 80% of all the lands in Hawaii below about 1500 feet (roughly 500 meters) in elevation had been extensively altered by humans (Kirch 1982)). This ecological site occurs well above that elevation. However, this ecological site may have been affected by factors such as inadvertently introduced plant diseases and seed predation by the introduced Pacific Rat (Athens 1997).

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.

The Polynesians introduced dogs, Pacific rats, and small pigs to the islands. 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 (Henke 1929). The most destructive introduced animals in this remote ecological site have been feral pigs and cattle.

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, birds, reptiles, amphibians, invertebrates, plants, and microorganisms, have brought about dramatic changes to wild ecosystems in Hawaii.

The main disturbances in this ecological site are due to feral pigs and goats that disturb the soil and directly consume native plants and rats that consume seeds. Some plant species introduced since the arrival of Europeans in Hawaii thrive in this ecological site and can spread rapidly over large areas, competing with native plants. The most abundant invasive plant species are broadleaf rush (Juncus planifolius) and common carpetgrass (Axonopus fissifolius).

State and transition model

Custom diagram

Standard diagram

Figure 1. State and Transition Model for the Poorly Drained Bog (R164XY401HI).

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. Weed-Invaded State

T1A	-	State 1, the Reference State, transitions to State 2, Weed-Invaded State, by invasion of introduced grass, sedge, rush, and forb species. Disturbance by feral cattle and pigs may hasten this process.
R2A	-	Restoration of State 2 Weed-Invaded State to State 1 Reference State or a facsimile of it may be possible by installing pig-proof fence, removing all ungulates, removing introduced species by hand weeding, and replanting native species when needed. Long term weed management and fence maintenance would be necessary. We are aware of no attempts at this restoration.

State 1 submodel, plant communities

1.1. Ohia lehua/Waialeale dubautia (naenae)/spiked beaksedge

State 2 submodel, plant communities

2.1. 2.1 Ohia lehua/Waialeale dubautia/ broadleaf rush – common carpetgrass

State 1
Reference State

This state is comprised of one community phase. With disturbance from hurricanes, landslides, or introduced mammals, invasive plants invade the site and native plant species decline in abundance.

Community 1.1
Ohia lehua/Waialeale dubautia (naenae)/spiked beaksedge

The vegetation of this community phase consists of sedges, rushes, and grasses with interspersed, low-stature shrubs, dwarf trees, and ferns. Lichens (Cladonia spp. and others) and mosses (Racomitrium lanuginosum and others) are abundant on the ground. Most of the vegetation is 0.5 to 10 inches (1 to 25 centimeters) tall. Shrubs and trees are 3 to 16 feet tall (1 to 5 meters).

Spiked beaksedge (Rhynchospora chinensis ssp. spiciformis) and claybank beaksedge (R. rugosa ssp. lavarum) are the most abundant cover; spiked beaksedge can reach 90% canopy cover. Alpine hairgrass (Deschampsia nubigena) is widespread at 2 to 5% cover. The taller uki or Polynesian twigrush (Machaerina angustifolia) typically occurs at 5 to 10% canopy cover. Hawaii Island sedge (Oreobolus furcatus), tussock panicgrass (Dichanthelium cynodon), and Maui rosette grass (D. isachnoides) cover can sometimes reach 40 percent and grow to 16 inches (40 centimeters) tall.

Common native forbs are Maui plantain (Plantago pachyphylla), Alakai Swamp island-daisy (Lagenifera erici) and Mt. Waialeale island-daisy (L. helenae). Common shrubs and small trees are ohia lehua (Metrosideros polymorpha) and Kauai bottlebrush (M. waialealae) growing to 16 inches (40 centimeters) tall, several species of Dubautia, and many other species (on the accompanying plant list, as are fern species).

Dominant plant species

'ohi'a lehua (Metrosideros polymorpha), tree
Waialeale dubautia (Dubautia waialealae), shrub
spiked beaksedge (Rhynchospora chinensis ssp. spiciformis), grass

State 2
Weed-Invaded State

This state is comprised of one community phase. It comes into being by gradual invasion of introduced species. Disturbance of the soil and direct damage to native plants by introduced ungulates, particularly pigs and cattle, will likely facilitate the transition to this state.

Community 2.1
2.1 Ohia lehua/Waialeale dubautia/ broadleaf rush – common carpetgrass

The vegetation consists of low-stature sedges, rushes, grasses, and forbs. Native species are present but have been partially displaced by introduced species. The most abundant introduced species are broadleaf rush (Juncus planifolius) and common carpetgrass (Axonopus fissifolius); less common species are in the accompanying plant list. The ground cover of lichens and mosses may have been disturbed and reduced by rooting feral pigs.

Dominant plant species

'ohi'a lehua (Metrosideros polymorpha), tree
Waialeale dubautia (Dubautia waialealae), shrub
broadleaf rush (Juncus planifolius), grass
common carpetgrass (Axonopus fissifolius), grass

Transition T1A
State 1 to 2

State 1, the Reference State, transitions to State 2, Weed-Invaded State, by invasion of introduced grass, sedge, rush, and forb species. Disturbance by feral cattle and pigs may hasten this process.

Restoration pathway R2A
State 2 to 1

Restoration of State 2 Weed-Invaded State to State 1 Reference State or a facsimile of it may be possible by installing pig-proof fence, removing all ungulates, removing introduced species by hand weeding, and replanting native species when needed. Long term weed management and fence maintenance would be necessary. We are aware of no attempts at this restoration.

Additional community tables

Table 6. Community 1.1 plant community composition

Group	Common name	Symbol	Scientific name	Annual production ()	Foliar cover (%)

Table 7. Community 2.1 plant community composition

Group	Common name	Symbol	Scientific name	Annual production ()	Foliar cover (%)

Supporting information

Other references

ANNOTATED REFERENCES

Armstrong RW. 1973. Atlas of Hawaii. University of Hawai`i Press, Honolulu. General reference for climate, land use, land forms, etc.

Athens JS. Ch. 12 Hawaiian Native Lowland Vegetation, IN Prehistory in Historical Ecology in the Pacific Islands – Prehistoric Environmental and Landscape Change. Kirch, PV and TL Hunt, eds. 1997. Yale U. Press, New Haven. General discussion of effects of prehistoric Polynesians on native lowland vegetation.

Burney DA, HF James, LP Burney, SL Olson, W Kikuchi, WL Wagner, M Burney, D McCloskey, D Kikuchi, FV Grady, R Gage II, and R Nishek. 2001. Fossil evidence diverse biota from Kauai and its transformation since human arrival. Ecological Monographs 71:615-641. Investigation of fossil evidence to trace changes in Hawaiian biota over time; generally applicable to all Hawaiian islands.

Craighill ES and EG Handy. 1991. Native Planters in Old Hawaii – Their Life, Lore, and Environment. Bernice P. Bishop Museum Bulletin 233, Bishop Museum Press, Honolulu, HI Discussion of early agriculture in Hawaii.

Cuddihy LW and CP Stone. 1990. Alteration of Native Hawaiian Vegetation: Effects of Humans, Their Activities and Introductions. Honolulu: University of Hawaii Cooperative National Park Resources Study Unit. General account of human effects on native Hawaiian vegetation.

Deenik J and AT McClellan. 2007. Soils of Hawaii. Soil and Crop Management, Sept. 2007, SCM-20. Cooperativve Extension Service, College of Tropical Agriculture and Human Resources. University of Hawaii at Manoa. Available online at: https://www.ctahr.hawaii.edu/oc/freepubs/pdf/SCM-20.pdf Discussion of soil orders and their practical implications in Hawaii.

Dixon JB and Schulze DG, eds. 2002. Soil Mineralogy with Environmental Applications. Volume 7. Soil Science Society of America. Available online at: https://acsess.onlinelibrary.wiley.com/doi/book/10.2136/sssabookser7 Exhaustive treatment of basics of soil mineralogy and implications for environmental management.

Giambelluca TW and TA Schroeder. 1998. Climate. In Atlas of Hawaii, 3rd edition. SP Juvik, JO Juvik, and RR Paradise, eds. pp. 49-59. Honolulu: University of Hawaii Press. Standard geographical reference work for Hawaii.

Hazlett RW and DW Hyndman. 1996. Roadside Geology of Hawaii. Mountain Press Publishing Company, Missoula MT. General account of geologic history of Hawaii.

Henke LA. 1929. A Survey of Livestock in Hawaii. Research Publication No. 5. University of Hawaii, Honolulu. Early assessment and history of effects of European livestock on Hawaiian ecosystems.

Imada, C. 2012. Hawaiian Native and Naturalized Vascular Plants Checklist (December 2012 update). Bishop Museum Technical Report 60. Bishop Museum Press, Honolulu. Constantly-updated list of vascular plants of Hawaii, including latest nomenclature and species occurrences on each island.

Jacobi JD. 1989. Vegetation Maps of the Upland Plant Communities on the Islands of Hawaii, Maui, Molokai, and Lanai. Technical Report 68. Cooperative National Park Resources Studies Unit, University of Hawaii at Manoa and National Park Service. Shapefiles of upland vegetation communities with canopy types, stature, environment types, and general species information.

Juvik JO and D Nullet. 1993. Relationships between rainfall, cloud-water interception, and canopy throughfall in a Hawaiian montane forest. In: Tropical Montane Cloud Forests. Proc. Int. Sym., San Juan, PR. Hamilton LS, JO Juvik, and FN Scatena, eds. East-West Center. Discussion of importance of fog drip to total precipitatiion in a montane forest.

Kirch PV. 1982. The impact of the prehistoric Polynesians in the Hawaiian ecosystem. Pacific Science 36(1):1-14. General discussion of effects of prehistoric Polynesians on native vegetation.

Kirch PV. 1985. Feathered Gods and Fishhooks: An Introduction to Hawaiian Archaeology and Prehistory. Honolulu: University of Hawaii Press. General discussion of effects of prehistoric Polynesians on native vegetation.

Kirch PV. 2000. On the Road of the Winds: An Archaeological History of the Pacific Islands Before European Contact. Berkeley: University of California Press. General discussion of effects of prehistoric Polynesians on native vegetation.

Little EL Jr. and RG Skolmen. 1989. Common Forest Trees of Hawaii (Native and Introduced). US Department of Agriculture-US Forest Service Agriculture Handbook No. 679. (out of print). Available at www.fs.fed.us/psw/publications/documents/misc/ah679.pdf Information on common native and introduced tree species in Hawaii. Especially useful for introduced species.

Mueller-Dombois D and FR Fosberg. 1998. Vegetation of the Tropical Pacific Islands. Springer-Verlag New York, Inc. General account of tropical Pacific Island vegetation, with section on Hawaii. Discussion of likely effect of stoniness on soil moistue storage in dry habitats.

Palmer DD. 2003. Hawaii’s Ferns and Fern Allies. University of Hawaii Press, Honolulu. Standard reference for Hawaiian ferns and fern allies.

Pratt HD. 1998. A Pocket Guide to Hawaii’s Trees and Shrubs. Mutual Publishing, Honolulu. Useful guide to common tree and plant species, with color photos.

Reppun F, Silva JHS, Wong K, and Deenik JL. 2017. A Soil Phosphorus Primer for Hawaiian Soils. Soil and Crop Management, August 2017, SCM-33. College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa. Available online at: https://www.ctahr.hawaii.edu/oc/freepubs/pdf/SCM-33.pdf Practical discussion of soil phosphorus for Hawaii.

Ripperton JC and EY Hosaka. 1942. Vegetation zones of Hawaii. Hawaii Agricultural Experiment Station Bulletin 89:1-60. Broad-scale map of vegetation zones in Hawaii.

Rock JF. The Indigenous Trees of the Hawaiian Islands. 1st edition 1913, reprinted 1974, Charles E. Tuttle Company, Rutland, VT and Tokyo, Japan. Very useful account observations of native vegetation in Hawaii from early 20th century. Can be paired with GIS layer of place names to locate species observations.

Shoji SD, M Nanzyo, and R Dahlgren. 1993. Volcanic Ash Soils: Genesis, Properties and Utilization. Elsevier, New York. Detailed discussion of volcanic ash soils. Not specific to Hawaii, but very informative.

Silva JA and R Uchida, eds. 2000. Plant Nutrient Management in Hawaii’s Soils, Approaches for Tropical and Subtropical Agriculture. College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa. Available online at: https://www.ctahr.hawaii.edu/oc/freepubs/pdf/pnm0.pdf Practical discussion of plant nutrient management for Hawaii.

Sohmer SH and R Gustafson. 2000. Plants and Flowers of Hawaii. University of Hawaii Press, Honolulu. A good general discussion, with color photographs, primarily of native Hawaiian plants and vegetation types.

Soil Survey Staff. 2014. Soil Taxonomy, Twelfth Edition. USDA – NRCS. Standard book of soil taxonomy; useful for terminology and interpretation of soils, also.

Steadman DW. 1995. Prehistoric extinctions of Pacific island birds: biodiversity meets zooarchaeology. Science 267:1123-1131. Discussion of loss of many bird species, including flightless birds.

USDA-NRCS-PIA Threatened & Endangered Species GIS files. Not publicly available. Specific locations of observations of many native Hawaiian plant species.

USDA-NRCS. 2011. Soil Survey Laboratory Information Manual. Soil Survey Investigations Report No. 45, Version 2.0. National Soil Survey Center, Lincoln, Nebraska.

USDA-NRCS. 2006. Major Land Resource Regions. USDA Agriculture Handbook 296. http://soils.usda.gov/MLRAExplorer Description of MLRAs of Hawaii.

USDA-NRCS. Island of Hawaii Soil Surveys 801 and 701. Available online at https://websoilsurvey.sc.egov.usda.gov/App/HomePage.htm The latest NRCS soil survey for the island of Hawaii.

USDA-SCS. 1972. Soil Survey of Islands of Kauai, Oahu, Maui, Molokai, and Lanai, State of Hawaii. Foote DE, Hill EL, Nakamura S, and F Stephens, in cooperation with The University of Hawaii Agricultural Experiment Station. The latest NRCS soil survey for these islands. Some of the taxonomic names are outdated.

USDI-USGS. 2006. A GAP Analysis of Hawaii. Final Report and Data. GIS map of vegetation types and land use in Hawaii based on remote sensing. Very general, occasionally inaccurate, but useful.

Vitousek P. 2004. Nutrient Cycling and Limitation: Hawai`i as a Model Ecosystem. Princeton University Press, Princeton and Oxford. Discussion of development of soils, soil nutrients, and plant species in Hawaiian Archipelago.

Wagner WL, DR Herbst, and SH Sohmer. 1999. Manual of the Flowering Plants of Hawaii, Revised Edition. Bishop Museum Press, Honolulu. Standard reference of flowering plants of Hawaii.

Western Regional Climate Center, cited 2020. Climate of Hawaii. Available: https://wrcc.dri.edu/Climate/narrative_hi.php Detailed summary of climate of Hawaiian Islands.

Whistler, WA. 1995. Wayside Plants of the Islands: A Guide to the Lowland Flora of the Pacific Islands. Isle Botanica, Honolulu. Reference of common introduced plant species in lowland areas of the Pacific Islands including Hawaii; with color photographs.

Wood, KR. 2006. Summary of Vascular Plant Research, Waialeale Summit Bog Region, Kauai, Hawaii. Botanical Report Prepared for the Department of Land and Natural Resources, Division of Forestry and Wildlife; the U. S. Fish and Wildlife Service; The Nature Conservancy of Hawai`i; and the Kaua`i Watershed Alliance (KWA). Detailed review of field work and general background for the Waialeale Summit Bog region, which covers this ecological site.

DEFINITIONS

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.

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 and duration 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.

Isomesic soil temperature regime: A regime in which mean annual soil temperature is 47 degrees F (8 degrees C) or higher but lower than 59 degrees F (15 degrees C) 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.

Makai: a Hawaiian word meaning “toward the sea.”

Mauka: a Hawaiian word meaning “toward the mountain” or “inland.”

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.

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 1500 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.

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

Udic soil moisture regime: A regime in which the soil is not dry in any part for as long as 90 cumulative days in normal years, and so provides ample moisture for plants. In Hawaii it is associated with forests in which hapuu (tree ferns) are usually moderately to highly abundant.

Contributors

David Clausnitzer
John Proctor
Mike Kolman
Carolyn Auweloa
Jennifer Higashino
Kendra Moseley
Mathew Cocking
Amy Koch

Approval

Kendra Moseley, 5/08/2025

Acknowledgments

Assistance, advice, review, and/or insights: Mick Castillo Michael Constantinides, NRCS-PIA Susan Cordell, USFS Gordon Cran, Kapapala Ranch David Foster, volunteer JB Friday, UH Forestry Extension Rick Gordon Basil Hansen, The Nature Conservancy Flint Hughes, USFS Chris Jasper, NRCS Soil Survey Mel Johansen, The Nature Conservancy Kathy Kawakami, US Army Pohakuloa Training Ground Rhonda Loh, Volcanoes National Park Kamehameha Schools/Bishop Estate Miles Nakahara, Hawaii DOFAW Laura Nelson, The Nature Conservancy and NRCS Patrick Niemeyer, NRCS Soil Survey Billy Paris, rancher John Pipan Jon Price, USGS John Replogle, The Nature Conservancy Paul Scowcroft, USFS Earl Spence, grazing consultant Jim Thain Mike Tomich Quentin Tomich Tim Tunison, Volcanoes National Park Jill Wagner, consultant, Future Forests Rick Warschauer

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	09/23/2026
Approved by
Approval date
Composition (Indicators 10 and 12) based on	Annual Production

Indicators

Number and extent of rills:
Presence of water flow patterns:
Number and height of erosional pedestals or terracettes:
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
Number of gullies and erosion associated with gullies:
Extent of wind scoured, blowouts and/or depositional areas:
Amount of litter movement (describe size and distance expected to travel):
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
Functional/Structural Groups (list in order of descending dominance by above-ground annual-production or live foliar cover using symbols: >>, >, = to indicate much greater than, greater than, and equal to):

Dominant:

Sub-dominant:

Other:

Additional:
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
Average percent litter cover (%) and depth ( in):
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
Potential invasive (including noxious) species (native and non-native). List species which BOTH characterize degraded states and have the potential to become a dominant or co-dominant species on the ecological site if their future establishment and growth is not actively controlled by management interventions. Species that become dominant for only one to several years (e.g., short-term response to drought or wildfire) are not invasive plants. Note that unlike other indicators, we are describing what is NOT expected in the reference state for the ecological site:
Perennial plant reproductive capability:

Download reference sheet

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