Botanical Survey of the Yela River Valley

Front Matter


Submitted to the

Institute of Pacific Islands Forestry U. S. D. A., Forest Service 1151 Punchbowl St., Room 323 Honolulu, HI 96813

David H. Lorence & Timothy Flynn of the
National Tropical Botanical Garden 3530 Papalina Road Kalaheo, Hawaii 96741 USA May 2005


A botanical survey of the Yela River valley in western Kosrae, F.S.M. was conducted to characterize the vegetation types (plant communities) in the area and determine their vascular plant species composition. The flora was documented by means of herbarium specimens, field identifications, and digital photos. Four vegetation types were recognized for the valley: (1) a well-developed fringing coastal mangrove forest occurs at sea level; (2) a majestic TerminaliaHorsfieldia swamp forest covers the valley bottom, extending to ca. 40-50 m elevation; (3) a lowland, non-swamp wet forest replaces it at elevations above ca. 20-30 m; (4) lower montane wet forest covers the rock outcrops, slopes, and ridges of the flanking mountains beginning at ca. 5 m . Ninety-nine vascular plant species and infra-species were recorded. Of these, 77 (77.8%) are indigenous, 13 (13.2%) are naturalized, 5 (5.2%) are endemic, and 4 (4.0%) are cultivated. The area supports a healthy, thriving forest with little disturbance, abundant seed production, numerous seedlings of all age groups, and very few naturalized plants, whose impact is minimal. This drainage area is a critical watershed for northwestern Kosrae. Its intact forest cover prevents erosion and damage to the coral reefs, while the mangroves buffer the coast and provide protection for juvenile marine organisms. This truly unique ecosystem serves as a valuable watershed that help protect the reef from siltation, serves as a reservoir for biodiversity on the island,


Kosrae, Federated States of Micronesia, botanical survey, vascular plants, mangrove forest, swamp forest, lowland, lower montane, wet forest


A botanical survey of the Yela River Valley (Infal Yela), Kosrae, F.S.M. was conducted for the Institute of Pacific Islands Forestry, USDA Forest Service, Pacific Region, by David Lorence and Tim Flynn of the National Tropical Botanical Garden, Hawaii. Three site visits were made on 31 January and 1-2 February 2005. Lorence and Flynn were accompanied by Kosrae staff members of the Kosrae Island Resource Management Authority (Killion Isisaki, Blair Charley, and Moses Palik) and Kosrae Conservation and Safety Organization (Marston Luckymis). In addition, Peace Corps Volunteers Jason Kramer and Julie Cooper accompanied the group on separate days.


The objectives of this project were to: (1) conduct three reconnaissance trips to distinguish and characterize the vegetation types and plant associations occurring in the area; (2) determine which vascular plant species (Pteridophytes and Angiosperms or flowering plants) occur in the area; (3) document the flora by collecting herbarium specimens for positive identification and taking digital photographs; and (4) produce a written report and checklist of the vascular flora accompanied by a CD with digital images of many of the species. Most of these photos were taken in Yela; the remainder were taken elsewhere on Kosrae and a few from cultivated plants. All photos were taken by D. Lorence.

Methods and Transects

The study area was accessed by a speedboat taken from Okat Harbor to the mouth of the Yela River in the mangrove zone. Exploration was done by using a walk- through method which covered all the plant communities and conducting visual surveys of the vegetation. A topographic map was used to determine the location of the transects. GPS readings could not be taken due to the dense forest canopy in most areas. The amount of time spent exploring the area was limited by weather and constraints imposed by boat access to the area. On day 1 (31 Jan. 2005) the southern (right hand) branch of the river was explored to c. 60 m. elevation. On day 2 (1 Feb. 2005) the main (left hand) branch of the river was explored to c. 80 m elevation. On day 3 (2 Feb. 2005) the N-NE- facing slope of the ridge flanking the southern mouth of the river was explored to c. 50 m. Visual plant identifications were made when the species were known. When identification was uncertain or species were not yet documented, herbarium specimens were collected for identification and deposition in the herbarium of the National Tropical Botanical Garden on Kauai, Hawaii (Herbarium PTBG). A complete checklist of the vascular plant species encountered during the survey is submitted as Appendix 1. Scientific names and authors, botanical family names, and Kosraean names where known, are listed in the checklist. Consequently authorities for the scientific names of species are not given in the text. A CD with digital images of many of the species is included as Appendix II of this report.

Botanical nomenclature is based largely on “A Geographical Checklist of the Micronesian Dicotyledonae” by Fosberg, Sachet, and Oliver, published in Micronesica 15 (1-2): 41—295. 1979). The monocots are from “A Geographic Checklist of the Micronesian Monocotyledonae” by Fosberg, Sachet, and Oliver, published in.Micronesica 20 (1-2): 18—129 (1987). The pteridophytes are from “A Geographical Checklist of the Micronesian Pteridophyta and Gymnospermae” by Fosberg, Sachet, and Oliver, published in Micronesica 18 (1): 1982). Families used in the checklist follow the Angiopsperm Phylogeny Website.