Assessing stable isotopes in koa trees may aid in reforestation efforts
Acacia koa is one of the most valuable tree species in the world and it only exists on the Hawaiian archipelago. Due to a variety of factors, such as introduction of invasive species, habitat degradation, and urbanization, the koa is at risk. Forest Service scientists are using knowledge about how stable isotopes in trees vary across elevation and precipitation gradients to identify favorable locations for koa reforestation. Forest Service researchers collected koa leaf samples along various elevation and precipitation gradients for 17 sites around the island of Hawaii. Analyses of isotopes of carbon and nitrogen, along with carbon and nitrogen percentages, were used to evaluate the sites. The sites consideredmost suitable for future restoration efforts were those with the greatest water-use efficiencies and the most negative nitrogen isotope ratios. Based on this data, the scientists ranked sites with respect to reforestation potential. Although a few similar small-scale research studies have been conducted on other islands, this is the first to include Hawai’i. It is critical that koa research address some of these most basic questions now before climate change and invasive flora and fauna exacerbate an already tenuous situation. Because koa trees are sacred to the Hawaiian people and slowly becoming endangered, work that scientists do to preserve this species is vital.