The Forest Inventory and Analysis (FIA) program conducted a systematic inventory of the forests of Rota, Tinian, and Saipan in the Commonwealth of the Northern Mariana Islands (CNMI) in 2004 to estimate forest area, tree stem volume, biomass, carbon storage, tree damages, and the composition and percentage cover of understory vegetation species.
Thirty-five permanent field plots were installed in a variety of forest types.
High-resolution satellite imagery was used to map land cover into five broad classes: forest, nonforest vegetation, urban, barren, and inland water. Soil survey information was used to help refine the classification of forests. Our estimates for this inventory are derived from a sample based on 75,407 acres on the three main islands in the CNMI.
- About 12 percent of the landscape was classified as urban land, the largest percentage found on Saipan (21 percent).
- We estimated gross tree stem volume to be about 66.5 million cubic feet for all size classes including seedlings and saplings.
- Aboveground dry biomass for tree stems 5 inches and greater was estimated to be about 563,000 tons.
- About 32 percent of the trees sampled in the inventory had some form of damage. Vines in the crown were the most prevalent damage type, followed by lost apical dominance, and conks. The most frequently identified damaging agents were damage from other vegetation (e.g., strangling or smothering vines) and weather.
- The CNMI’s forests are composed of small-diameter trees and have relatively low species diver¬sity compared to other Pacific Islands. In total, 57 tree species and 107 understory species were measured on the FIA plots. The average number of tree species per one-sixth-acre plot was five.