Northern Guam geospatial information server

Vegetation of Guam

Plant communities and vegetation resources of Guam have been studies by Fosberg (1960), Raulerson and others (1978), Mueller-Dombois and Fosberg (1998) and US Department of Agriculture (20002). According to these researchers, Guam hosts a diverse flora of over 600 species of vascular plants, including more than 100 species of trees. The distribution of vegetation is influenced by two main factors, the sharply contrasting soil types between the north and south and anthropogenic (e.g. urban development and fire) and natural (i.e. windthrow from hurricanes) disturbances.

Consequently, vegetation in the north is dominated by thick secondary scrub and urban vegetation (i.e., lawns and ornamental trees and shrubs) inland, and by strand and limestone forests in coastal areas. The high elevation of the limestone plateau prevents the root zone from reaching the freshwater lens. In the south, vegetation is dominated by savanna and patches of forest, mostly riverine forests that form along valleys and ravines. The low-lying portions of river valleys are occupied by swamp forests, marshes, and occasional cultivated clearings.

The USDA Forest Service established the following classification of vegetation on Guam:

1. Limestone and strand forest
--> (on elevated limestone plateaus and cliffs)
2. Savanna Complex
--> (on hilly volcanic terrain)
3. Swamp Forest Complex, including Mangroves
--> (in low-lying river valleys)
4. Marshes
--> (in depressions on volcanic terrain)
5. Ravine Forest
--> (on volcanic soil in river valleys)
6. Secondary and Partially Cultivated Scrub Forest
--> (in disturbed areas and remnants of old agroforest)
7. Coconut Plantation
--> (in limited coastal areas)
8. Urban Vegetation
--> (in towns and around military installations)

The full scope of vegetation types can be recognized only in southern Guam. The northern Guam is dominated by secondary scrub forest and urban vegetation, with patches of limestone and strand forest on coastal terraces and remote locations (especially Ritidian and Pati points), limited savanna on volcanic inlier terrain (Mt. Santa Rosa and Mataguac Hill), and coconut plantations in prominent coastal embayments (notably Haputo and Tarague).

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