Wetland Classification

On the basis of a classification scheme developed by Dansereau and Segadas-Vianna (1952) and Rigg (1942), "...the area of Kawainui Marsh must be divided into two types: (1) a bulrush marsh with floating mat of live vegetation and peat development and (2) a bog meadow of California grass, flooded only during the rainy season and resting on mineral soil rather than peat. Both types are stream fed."¹

Vegetation

Perhaps the most conspicuous characteristic of Kawai Nui Marsh today is the predominance of vegetation, both floating and standing, which covers most of the 900-acre expanse of the marsh, giving it a deceptive appearance, from a distance, of being a lush green pasture. Upon closer examination, however, it becomes apparent that even the cattle confine themselves to grazing the upper, wet meadow end and edges, and that the vast interior remains a deep, vegetation-clogged body of water.

The vegetation comprising Kawai Nui Marsh can be divided into several distinct plant communities:

1. a grass community, consisting principally of California grass (Brachiaria mutica) interspersed with honohono (Commelina diffusa), arrowhead (Sagittaria latifolia), and scattered stands of cattail (Typha latifolia). California grass is a very aggressive and dominant species. It is a large perennial grass which forms dense patches with long runners up to (in the marsh) two and a half meters tall. Its leaves have hairy sheaths and blades up to 25 cm. long and one and a half cm. across.²

   California grass can establish thick mats in wet areas such that "...ponds have been completely lost to view because of the floating layers of vegetation thick enough to support the weight of grazing cattle."⁴

2. a bulrush community, consisting of kaluha or bulrush (Schoenoplectus californicus), sawgrass (Cladium jamaicense), and neke or swamp fern (Cyclosorus interruptus). Bulrush is a tufted sedge with erect, round or slightly angled stems 30 to 90 cm tall. Its leaves are reduced to basal sheaths. Bulrush is able to flourish in a wetland such as Kawai Nui because its interior is made of sponge-like air spaces. These air spaces enable the bulrush to extract oxygen out of the water.²

The grass and bulrush communities each occupy approximately equal areas in the marsh. Together they occupy several hundred acres of the wetland, rendering much of the marsh worthless as a waterbird habitat by occluding or covering open water areas. In moderation, however, these communities could provide valuable nesting and feeding areas if numerous potholes and channels were opened up throughout the area.³
3. a shrub and tree community. On the outer edges of the grass and bulrush plant communities along the slopes above the marsh, there exists a tree and shrub community consisting primarily of koa haole (Leucaena leucocephala), guava (Psidium guajava), Chinese banyan (Ficus microcarpa) and Monkeypod (Samanea saman). Linda Smith noted about 119 plant species occurring in this area; eight of which were native, but no endangered species, while 24 of them occurred throughout the entire marsh.³

4. an open-water community, which exists along the inner edges of the grass and bulrush communities, in the marsh interior, as well as in the canals entering and exiting the marsh.
The open-water community consists of the floating vegetation, which is rapidly taking over the already greatly diminished open water areas of the marsh. A dominant species in this area is water lettuce (Pistia stratiotes), a floating aquatic herb with a rosette of leaves and abundant dangling dark roots.

Water lilies (Nymphaea sp.) and the water hyacinth (Eichhornia crassipes) are by far the predominant floating plant species which occupy the remaining open space in the marsh interior. Nymphaea are a very recent introduction into the marsh, having been unrecorded in the open water of the main pond until 1978.³

We can easily recognize that the nature of a marsh encourages habitation by both terrestrial and aquatic animals. This characteristic is even more pronounced at Kawai Nui where the water surface is extensively covered by floating peat, supporting both aquatic and non-aquatic plants. By definition, aquatic animals live in and on bodies of water, and terrestrial animals inhabit the emergent plants and dry outcrops of soil. In some cases, it is difficult to assign this classification to a particular animal: a dragonfly is a flying (land) animal, but it's juvenile stage is aquatic).

See...

• Aquatic biota listing at Na Pohaku o Hauwahine
• Terrestrial animals at Na Pohaku o Hauwahine
• Keys to the Aquatic Biota of the Hawaiian Islands

PAGE INFORMATION SOURCES:

¹ Linda L. Smith. 1978. Development of emergent vegetation in a tropical marsh. MS Thesis, U.H., Botany. p. 6, 15-16.
Dansereau, P. and F. Segadas-Vianna. 1952. Ecological study of the peat bogs of eastern North America. Can. J. Bot., 30: 490-520.
Rigg. 1942. [Reference cited but not provided by Smith].

(Vegetation Section text modified from): Diane C. Drigot, IS 489 Environmental Practicum Students, and Muriel B. Seto. 1982. Ho`ona`auao no Kawai Nui (Educating about Kawai Nui). A multi-media educational guide, Chapter 5, pp.128-133. And the following where indicated:
² Ai-Chang, Mitchell. 1982. A preliminary report on Kawainui Marsh plants by Ecology Camp Students. Highschool Ecology Camp participant
³ Shallenberger, Robert. 19??. Kawainui Marsh, an evaluation of the feasibility of developing it into a National Wildlife Refuge. U.S. Fish & Wildlife Service, Honolulu, p. 5.
⁴ Bown, T.A., C. Lyman, and P.P. Rotar. 1966. Paragrass or Claifornia grass. Coop. Exten. Serv., U. H.. Leaflet 106. Conserv. Sers. Honolulu.

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