Inluded here are the Caroline Islands, Mariana Islands, Marshall Islands, Gilbert Islands, Ellice Islands, Phoenix Islands, Tokelau Islands, Baker Island, Banaba Island, Howland Island, Nauru Island and Wake Island.

The upland volcanic parts of many of the higher islands support grasslands of varying extent. These are generally referred to as savannas although they are normally not flat and trees may be absent. On Guam the dominant grasses include the endemic Dimeria chloridiformis (Poaceae), a tufted, soft bluish-green grass that occurs on the more level or gently sloping areas, or on the steeper slopes and ridges, Miscanthus floridulus, a coarse, sharp edged, cane like-grass that can reach heights of 3 m. The few trees may include Casuarina equisetifolia or the endemic Xylosma nelsonii (Flacourtiaceae).  Other associated endemic species include the shrubs Alyxia torresiana (Apocynaceae), Melastoma marianum (Melastomataceae), Myrtella bennigseniana (Myrtaceae), Pandanus fragrans forma savannarum (Pandanaceae), Timonius nitidus (Rubiaceae) and the herbaceous species Hedyotis megalantha (Rubiaceae). However, many of the characteristic savanna plants are pioneer species that rapidly colonize any denuded areas. The deeply weathered volcanic rocks on Guam often undergoes extensive erosion leaving bare scars for colonization by these species, while the more mature areas may be composed of almost monospecific grasslands. 

References

Balgooy, Van. M. M. J. 1960. Preliminary plant geographical analysis of the Pacific. Blumea, 10: 385-430.

Fosberg, F. R. 1960. The vegetation of Micronesia. Bulletin of the American Museum of Natural History, 119: 1-75.

Fosberg, F. R., Sachet, M. H. & Oliver, R. 1979. A Geographical Checklist of the Micronesian Dicotyledonae. Micronesica, 15: 41-295.

Fosberg, F. R. 1984. Phytogeographic comparison of Polynesia and Micronesia. In: Biogeography of the Tropical Pacific (Proceedings of a Symposium). Eds. F. J. Radovsky, P. H. Raven and H. Sohmer. Bishop Museum Special Publication No. 72.

Gillison, A. M. 1983. Tropical Savannas of Australia and Southwest Pacific. In: Ecosystems of the World 13 - Tropical Savannas. Ed. F. Bourliere. Elsevier Scientific Publishing Company.

Mueller-Dombois, D. & Fosberg, F. R. 1998. Vegetation of the Tropical Pacific Islands. Springer.

Stone, B. C. 1970-71. The Flora of Guam. Micronesica, 6: 1-659.