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Ecological site VX161A01X002

High Elevation Isomesic Desert

Last updated: 4/17/2025
Accessed: 04/29/2025

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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): 161A–Lava Flows and Rock Outcrops

This MLRA occurs in the State of Hawaii on the Big Island of Hawaii and to a small extent on Maui. Elevation ranges from sea level to 13,796 feet (0 to 4,206 meters), which includes the tops of Mauna Kea, Mauna Loa, Haleakala, Kilauea, and Hualalai volcanoes. Slopes follow the undulating to very steep topography of the lava flows. The terrain includes barren lava flows, rocky cliffs, rock outcrops, and steep cinder cones. Lava flows are basaltic aa or pahoehoe lava. Average annual precipitation ranges from 10 to 100 inches (255 to 2,540 millimeters). Most of the rainfall occurs from October through March in most areas and from May through September in the Kona area of the Big Island. In Kona and isolated areas elsewhere, afternoon fog accumulation at higher elevations adds significant moisture by fog drip and ameliorates evapotranspiration. This effect is cut off sharply at the atmospheric inversion layer at about 6,000 feet (about 2,000 meters) elevation. Average annual air temperatures range from 38 to 76 degrees F (3 to 25 degrees C), with little seasonal variation. Freezing temperatures occur at the highest elevations. Dominant soils are Andisols and Histosols with isohyperthermic to isofrigid soil temperature regimes and ustic to udic soil moisture regimes. Large parts of the MLRA consist of miscellaneous (nonsoil) areas, including lava flows, rock outcrop, and cinder land. Native vegetation varies considerably as temperature, moisture, and soil development vary with elevation and flow age. In the driest areas near sea level, sparse, low-stature shrubs, grasses, and forbs predominate. Vegetation stature and density gradually increase with elevation to typical dry forest species such as lama, wiliwili, and alahee, koa-mamane-sandalwood or mamane-sandalwood forest, open ohia-lovegrass savanna, and finally sparse subalpine vegetation with silversword, shrubs, and grasses. Vegetation is extremely sparse at the highest elevations.

Classification relationships

This ecological site occurs within Major Land Resource Area (MLRA) 161A - Lava Flows and Rock Outcrops.

Ecological site concept

This ecological site is a mosaic of shrubs, grasses, and trees that occurs at the highest vegetated elevations around the summit of Mauna Kea on Hawaii. Most of the area is owned by the State of Hawaii and is accessible to visitors. The easiest access is along the Mauna Kea summit road on the way to the telescopes complex.

The central concept of the High Elevation Isomesic Desert is of well to somewhat excessively drained, mostly deep and very deep soils formed in deposits of volcanic ash and, in some areas, glacial outwash, pumice, and eolian sand. It occurs between elevations of about 9100 to 10,900 feet (2800 to 3350 meters). Annual air temperatures and rainfall are associated with cool (isomesic), seasonally dry (ustic) soil conditions. The vegetation is a patchwork of bare soil and rock with stands of shrubs and trees with shrubs, and areas of open, sparse bunchgrasses. Hawaii silversword (Argyroxiphium sandwicense ssp. sandwicense), one of the Hawaiian silverswords, was widespread in the past but is now restricted to protected areas and very high elevations with few introduced ungulates.

Associated sites

VX160X01X501	Ustic Fog Drip Forest The Ustic Fog Drip Forest adjoins this ecological site on Mauna Kea, where it occupies lower elevations. It has similar soils, higher temperatures, higher rainfall, and gains more soil moisture from fog drip compared with this ecological site. It supports more abundant, productive, and diverse vegetation than this ecological site.

VX160X01X501

Ustic Fog Drip Forest

The Ustic Fog Drip Forest adjoins this ecological site on Mauna Kea, where it occupies lower elevations. It has similar soils, higher temperatures, higher rainfall, and gains more soil moisture from fog drip compared with this ecological site. It supports more abundant, productive, and diverse vegetation than this ecological site.

Table 1. Dominant plant species

Tree	(1) Dubautia arborea
Shrub	Not specified
Herbaceous	(1) Argyroxiphium sandwicense ssp. sandwicense (2) Trisetum glomeratum

Legacy ID

R161AY002HI

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Physiographic features

This ecological site occurs on ash fields deposited over lava flows on mountain slopes of shield volcanoes. Lava flows are aa (loose, cobbly) or pahoehoe (smooth, relatively unbroken).

Table 2. Representative physiographic features

Landforms	(1) Shield volcano > Ash field (2) Shield volcano > Lava flow
Runoff class	Low to very high
Flooding frequency	None
Ponding frequency	None
Elevation	9,100 – 10,900 ft
Slope	6 – 50%
Water table depth	60 in
Aspect	W, NW, N, NE, E, SE, S, SW

Table 3. Representative physiographic features (actual ranges)

Runoff class	Not specified
Flooding frequency	Not specified
Ponding frequency	Not specified
Elevation	8,600 – 10,900 ft
Slope	Not specified
Water table depth	Not specified

Climatic features

Average annual precipitation ranges from 20 to 35 inches (500 to 890 millimeters). Most of the precipitation falls from through October through April. Snow occurs at the highest elevations in winter in some years. Average annual temperature ranges from 45 to 57 degrees F (7 to 14 degrees C). The frost-free period is 150 to 250 days.

Table 4. Representative climatic features

Frost-free period (characteristic range)	150-250 days
Freeze-free period (characteristic range)	365 days
Precipitation total (characteristic range)	20-35 in
Frost-free period (average)	222 days
Freeze-free period (average)	365 days
Precipitation total (average)	27 in

Soil features

The soils correlated with this ecological site are classified as Andisols. Most have vitric mineralogy (high content of volcanic glass), giving them low water holding capacity. Soil temperature regimes are isomesic; soil moisture regimes are ustic.

Table 5. Representative soil features

Parent material	(1) Basic volcanic ash – basalt (2) Till
Surface texture	(1) Medial sandy loam (2) Ashy loamy sand
Family particle size	(1) Ashy (2) Medial-skeletal
Drainage class	Somewhat excessively drained to well drained
Permeability class	Moderate to rapid
Depth to restrictive layer	11 – 72 in
Soil depth	11 – 72 in
Surface fragment cover <=3"	10 – 45%
Surface fragment cover >3"	15 – 35%
Available water capacity (0-40in)	2 – 3 in
Electrical conductivity (0-40in)	2 mmhos/cm
Sodium adsorption ratio (0-40in)	Not specified
Soil reaction (1:1 water) (0-40in)	4.5 – 7.8
Subsurface fragment volume <=3" (0-40in)	20 – 40%
Subsurface fragment volume >3" (0-40in)	20 – 50%

Table 6. Representative soil features (actual values)

Drainage class	Not specified
Permeability class	Very slow to rapid
Depth to restrictive layer	Not specified
Soil depth	Not specified
Surface fragment cover <=3"	Not specified
Surface fragment cover >3"	Not specified
Available water capacity (0-40in)	Not specified
Electrical conductivity (0-40in)	Not specified
Sodium adsorption ratio (0-40in)	Not specified
Soil reaction (1:1 water) (0-40in)	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.

The natural (not human-caused) disturbance most important for discussion in this ecological site fire caused by lightning. However, most parts of this ecological site have discontinuous vegetation with much bare soil and areas of rock outcrop, so extensive natural fires are rare and limited in extent.

The most severe impacts in this ecological site have been caused by feral goats, feral sheep, and mouflon sheep grazing and browsing the native grasses, shrubs and trees, none of which evolved with land mammals of any kind except for a native bat. Domestic cattle and sheep have been grazed on some low- to mid-elevation parts of the ecological site. This ecological site has been invaded by introduced plant species, particularly grasses, that compete with and displace native plants to some extent. Human-caused wildfires have affected some limited areas.

State and transition model

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Standard diagram

Figure 1. State and Transition Model for R161AY002HI (High Elevation Isomesic Desert)

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. Grazed and Browsed State

T1A	-	State 1 Reference transitions to State 2 Grazed and Browsed by reduction or loss of native species due to grazing and browsing by introduced or domestic ungulates and by invasion by introduced plant species.
R2A	-	State 2 Grazed and Browsed may be restored to State 1 Reference State by excluding all ungulates. Spot weed removal must be done initially and continued in the long term. Missing native plant species can then be reintroduced.

State 1 submodel, plant communities

1.1. Mauna Kea dubautia/Hawaii silversword/pili uka

State 2 submodel, plant communities

2.1. Pukiawe/common mullein/common velvetgrass – sweet vernalgrass

State 1
Reference State

This state consists of one community phase. Much of this ecological site is of marginal value as grazing land. However, disturbance by introduced ungulates results in loss of native species or reductions in their abundance that cause this state to transition to State 2 Grazed and Browsed.

Community 1.1
Mauna Kea dubautia/Hawaii silversword/pili uka

Figure 2. State 1, very high elevation. Silverswords. David Clausnitzer, 9/07/2010.

Figure 3. State 1 Reference. Very high elevation area. David Clausnitzer, 12/30/09.

Figure 4. State 1 Reference. Black cinder dunes. David Clausnitzer, 12/30/09.

Figure 5. State 1, very high elevation. Silversword plant. David Clausnitzer.

Figure 6. Site near summit at higher elevation than this ecological site with winter snow. There is some very sparse vegetation here. David Clausnitzer 1/6/09.

Figure 7. Near Mauna Kea Visitor Center. Ice crystals in soil. David Clausnitzer 1/6/09.

Figure 8. State 1. Area near summit in snow-free season showing very sparse vegetation. David Clausnitzer, 1/6/09.

Figure 9. Fence line of ungulate exclosure. State 1 on left, State 2 on right.

The lower elevation parts of this ecological site are savanna or woodland with an open to nearly closed canopy of low-stature trees interspersed with stands of shrubs. Vegetation density decreases rapidly with increasing elevation, becoming open savanna, then open shrubland with abundant grass, and finally very open shrubland with some grasses. Overall, grass/grasslike canopy cover ranges from 5 to 70 percent. Severe historic disturbance by ungulates makes estimates of vegetation abundance species ranges in the reference state difficult, although relatively small long-term exclosures provide some information. The tree overstory, where present, consists primarily of mountain pilo or alpine mirrorplant (Coprosma montana), naio (Myoporum sandwicense), mamani (Sophora chrysophylla), and Mauna Kea dubautia (Dubautia arborea). Common shrubs are pukiawe (Leptocophylla tameiameiae), and ohelo ai (Vaccinium reticulatum). Hawaii silversword (Argyroxiphium sandwicense ssp. sandwicense) was common in the past but is now limited to outplantings and protected areas. Western brackenfern (Pteridium aquilinum) and Trans-Pecos cliffbrake (Pellaea ternifolia) are common ferns. Common grasses are alpine hairgrass (Deschampsia nubigena) and pili uka (Trisetum glomeratum). Some common forbs are littleleaf stenogyne (Stenogyne microphylla), maohiohi (Stenogyne rugose), alpine catchfly (Silene struthioloides), and alpine tetramolopium (Tetramolopium humile).

Dominant plant species

Mauna Kea dubautia (Dubautia arborea), tree
pili uka (Trisetum glomeratum), grass
Hawai'i silversword (Argyroxiphium sandwicense ssp. sandwicense), other herbaceous

State 2
Grazed and Browsed State

This state consists of one community phase. It differs from State 1 Reference by having lower diversity and production of native species due to disturbance by ungulates and competition from introduced plant species.

Community 2.1
Pukiawe/common mullein/common velvetgrass – sweet vernalgrass

Figure 10. State 2. Landscape view. David Clausnitzer, 12/30/09.

Figure 11. State 2 outside ungulate exclosure. East face of Mauna Kea. David Clausnitzer, 12/30/09.

Figure 12. State 1 inside ungulate exclosure. East face of Mauna Kea. David Clausnitzer, 12/30/09.

The original woodland or savanna structure is present in many places, with native trees and native shrubs. The grass stratum has become dominated by introduced species, with some native grasses still present. Seedlings and saplings of native trees and shrubs are uncommon or not present. Introduced forbs are widespread, while native forbs and vines have become rare. Remaining native trees have been damaged or killed by heavy browsing.

Dominant plant species

pukiawe (Styphelia tameiameiae), shrub
common velvetgrass (Holcus lanatus), grass
sweet vernalgrass (Anthoxanthum odoratum), grass
common mullein (Verbascum thapsus), other herbaceous

Transition T1A
State 1 to 2

State 1 Reference transitions to State 2 Grazed and Browsed by reduction or loss of native species due to grazing and browsing by introduced or domestic ungulates and by invasion by introduced plant species.

Restoration pathway R2A
State 2 to 1

State 2 Grazed and Browsed may be restored to State 1 Reference State by excluding all ungulates. Spot weed removal must be done initially and continued in the long term. Missing native plant species can then be reintroduced.

Additional community tables

Supporting information

Other references

ANNOTATED REFERENCES

Abrahamson I. 2013. Fire regimes in Hawaiian plant communities. In: Fire Effects Information System, US Dept. of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. Available" www.fs.fed.us/database/feis/fire_regimes/Hawaii/all.html Review of fire regimes and history for multiple generalized plant communities in the Hawaiian Islands.

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.

Clark JT. 1983. Report 3: The Waimea-Kawaihae Region: Historical Background. In Archaeological investigations of the Mudlane-Waimea-Kawaihae Road Corridor, Is of Hawaii: an Interdisciplinary Study of an Environmental Transect. Clark JT and Kirch PV, eds. Dept. of Anthropology, Bernice Pauahi Bishop Museum, Report 83-1, Honolulu, HI. Study done in Kohala describing historical impacts on a transect crossing multiple environmental zones and vegetation types.

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.

Dougill, S and T Rogers. Plants of the Subalpine Forests of Mauna Kea. USGS-BRD, PIERCE, Kilauea Field Station, PO Box 44, HAVO, HI 96718. Description of many of the native species of this ecological site.

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.

Hartt CE and MC Neal. 1940. The plant ecology of Mauna Kea, Hawaii. Ecology 21:2 pp. 237-266. Survey of Mauna Kea vegetation.

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 existing forests with dominant species, general environment type, canopy height, and canopy closure.

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.

DEFINITIONS

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

Aa lava: A type of basaltic lava having a rough, jagged, clinkery surface and a vesicular interior.

Ash field: a land area covered by a thick or distinctive deposit of volcanic ash that can be traced to a specific source and has well defined boundaries. The term “ash flow” is erroneously used in the Physiographic section of this ESD due to a flaw in the national database.

Ashy: A “soil texture modifier” for volcanic ash soils having a water content at the crop wilting point of less than 30 percent; a soil that holds relatively less water than “medial” and “hydrous” soils.

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.

Friability: A soil consistency term pertaining to the ease of crumbling of soils.

Ion exchange capacity: The ability of soil materials such as clay or organic matter to retain ions (which may be plant nutrients) and to release those ions for uptake by roots.

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.

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.

Pahoehoe lava: A type of basaltic lava with a smooth, billowy, or rope-like surface and vesicular interior.

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.

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

David Clausnitzer
John Proctor
Mike Kolman
Carolyn Wong
Kendra Moseley
Mathew Cocking
Michael Constantinides
Jennifer Higashino

Approval

Kendra Moseley, 4/17/2025

Acknowledgments

Assistance, advice, review, and/or insights:

Randy Bartlett, Puu Kukui Watershed Preserve
Alison Cohan, The Nature Conservancy
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, Maui
Wallace Jennings, 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	04/19/2025
Approved by	Kendra Moseley
Approval date
Composition (Indicators 10 and 12) based on	Annual Production