by Diana Duff
Special To West Hawaii Today
Sunday, December 5, 2010 7:40 AM HST
Many gardeners in Hawaii have become native plant enthusiasts. More and more people are awakening to the beauty of our native species and learning about them and the vigilance required to save them from harm or eventual extinction. Events like Arbor Day at Amy B.H. Greenwell Ethnobotanical Garden, offering free native plants and information on growing them, help folks learn ways to grow and care for native plants. Interest in these plants, which have thrived in our native forests for millennia, helps raise awareness of the threats a multitude of invasive species pose to them.
One particularly threatening species, the autograph, or signature, tree (Clusia rosea) caught the notice of Darcy Ames, who has witnessed firsthand the encroachment of this species on the ohia forests near her home.
“When I first bought property in Holualoa, I thought the autograph tree was quite lovely,” Ames said. “After a few years of experience, inspection and investigation, I began to realize this tree was capable of destroying the habitat of our ohia and other native species unless we began a proactive course against it.
“After witnessing the damage it can cause, I can honestly say that I hate what this plant is capable of doing. Autograph seeds can be dropped by birds and root as much as 20 or 30 feet in the air in the crotch of an ohia tree.
Several nonprofit organizations, a state agency and three local counties have been awarded $3.3 million from a state land preservation fund to protect 753 acres on the Big Island, Kauai, Molokai and Oahu.
The money from the Legacy Land Conservation Program will be matched with about $9.5 million from federal, county and private sources to acquire land or protective easements for public benefit.
Seven projects are being financed, including four land purchases totaling 25 acres and three easements covering 728 acres.
Laura Thielen, chairwoman of the state Board of Land and Natural Resources, said the fund provides an efficient way to protect land containing important natural, cultural or agricultural value. “By providing these grants as incentive, the state is utilizing mostly private and federal funds to protect these resources,” she said in a statement announcing the awards.
Vegetation in an area may determine its usable water supply, ecologists find
Ecologists have discovered that timber plantations in Hawaii use more than twice the amount of water to grow as native forests use. Especially for island ecosystems, these findings suggest that land management decisions can place ecosystems – and the people who depend on them – at high risk for water shortages.
"Scientists used to think that forests in same environments use water in the same way," says Lawren Sack of The University of California at Los Angeles, who coauthored the study with graduate student Aurora Kagawa in the September issue of the ESA journal Ecological Applications. "Our work shows that this is not the case. We need to know the water budget of our landscape, from gardens to forests to parks, because water is expensive."
Although forests like these Hawaiian timber plantations can be valuable for their contributions to human society, such as fiber, fuel and carbon sequestration, they are dominated by non-native vegetation.
Kagawa, Sack and their colleagues compared the water use of trees in native forests, composed mostly of native ohia trees, with water use in timber plantations containing exotic eucalyptus and tropical ash. The team inserted heated and unheated probes into the trees’ trunks and monitored the temperature differences between the two as sap flowed past them. This technique allowed them to determine the rate of sap flow through the tree. A faster flow rate means that the tree is using more water.