Koa Forest in Kokeʻe: Recovery and Threats Hi I’m J.B. Friday, Extension Forester with the University of Hawaiʻi. We’re here on another koa field day. We’re standing here today in the Kokeʻe State park on the island of Kauaʻi. Weʻre at a forest and elevation of about 3,800 feet. This forest that you see here was completely destroyed by Hurricane Iwa in 1982. After the koa trees that were here were knocked down The logs were harvested and the action of harvesting by the machinery stirred up the seed in the soil. That seed sprouted and grew into the koa forest we see today. So we know these trees are about 27 years old and They average about seven inches in diameter. When we look up above us into the canopy, we see that the canopy is almost entirely koa. All these koa trees that we see here germinated at the same time, that was right after the salvage logging after the 1982 hurricane, so they’re all the same age. They regenerated very densely and they compete with each other as they grow. So today what we see is a few healthy trees that have a healthy crown up in the canopy and many other trees that have been overtopped and die out once they get shadowed, because again the koa trees need light to continue to grow. This tree died several years ago. This tree was in the canopy but just died recently. When we look on the forest floor here, we see a lot of koa seedlings. The pigs here stir up the soil and caused the seedlings to germinate. We see lots of small seedlings in the ground. These came from last year’s seed. We don’t see any seedlings that are two years old so probably none of these little seedlings that have germinated here will make it. When we look above the koa seedlings we see a solid koa canopy. Now koa seedlings need light to grow and underneath the canopy of koa trees they can’t survive, That’s why we see a lot of seedlings but nothing growing up into saplings. The other part of the problem here is this forest is being taken over by the alien species strawberry guava. The strawberry guava comes in in dense thickets here, it’s very shady underneath it. It doesn’t allow the koa or any other native species to regenerate underneath it. This forest isn’t only valuable for koa and bird habitat it’s also valuable for native plants especially useful plants such as the maile vine. People pick the maile to make lei for special events especially during graduations. Another culturally important plant here is the palapalai fern. Palapalai is collected and used for making lei poʻo and other lei — it’s especially important for the hula. I’m pretty surprised to see so much guava at 3,800 feet at this elevation. Usually guavaʻs found more at the lower elevation, warmer forests. This forest will be really too bad if the guava takes over because not only are we losing the koa We’ll lose all the other plants that are important both for the natural history and the culture, like the palapalai and the maile. Another problem invasive species here in the forest and Kokeʻe is the kahili ginger. Kahili ginger it is an ornamental, has a beautiful flower, and it looks great in the gardens but birds spread the seed, it grows all throughout the forest, can form solid mats that choke out any regeneration of native plants underneath it. This forest is of course vulnerable to storm damage. Last winter we had a lot of rain which soaked the soil and loosened the tree’s roots and a number of koa trees like this one fell over. When a koa tree falls over, it opens up a gap in the canopy let sunlight in. In the natural scheme of things, when you have a gap in the forest canopy, that allows light down to the forest floor and you get regeneration of the koa seedlings. However in this forest what we’re getting is strawberry guava and the alien ginger that are taking over the forest. In the long run, if these alien species aren’t controlled, we’re going to lose the whole forest here. Here, we have an old koa that’s split in half and died but instead of young koa seedlings growing up underneath it, the entire understory is taken over by a dense thicket of karaka nut. Strawberry guava grows out of control here Hawaiʻi because it doesn’t have any natural enemies. The good news is scientists through the U.S. Forest Service have gone to Brazil found some of the natural enemies of the strawberry guava and have spent years testing it to make sure that those natural enemies don’t predate on any Hawaiian native plants. They’re waiting for permission to release these insects here in Hawaiʻi to predate on the strawberry guava, to slow it down, to allow the native plants some chance of competing. There are other problems with the health of this forest. A number of trees have died from diseases. This tree, for example, was a large healthy koa that died since we’ve been measuring it in the past three years. We’re currently working on a project to map areas of koa dieback in the forest to help managers get a handle on the problem. Hi. I’m Travis Idol, Research Forester with the University of Hawaiʻi. As part of our overall project, we’re collecting koa leavess from the top of the canopy. The reason we’re doing this is we think leaves are a good indicator of the overall health and productivity of the forest stand. So we’re collecting leaves and we’ll be taking them back to the laboratory to analyze them for leaf thickness, greenness, as well as nutrient concentration, to give us an overall indicator of how healthy and productive this forest stand is. Dr. Travis Idol and Rodolfo Martinez Morales are using a pruning pole to collect leaves from the top of the canopy here. The pruning pole is over 40 feet long, so we can collect leaves from the very top of the canopy. Weʻll analyze these leaves back in the lab for nutrients to determine the nutrition of the koa trees in this forest. i’m getting a headache… not enough coffee? too much coffee? need water? or need more coffee? For more information contact: Dr. J.B. Friday, Extension Forester, 875 Komohana St, Hilo HI 96720
https://cms.ctahr.hawaii.edu/forestry/ For more information contact: Travis Idol, Research Forester, Tropical Forestry & Agroforestry, Dept. of Natural Resoures and Environmental Management, University of Hawaiʻi at Manoa,
email: [email protected]
phone: 808-956-750 Acknowledgements
Jody Smith, Education Specialist, UH-CTAHR RREA Program
Rodolfo Martinez Morales, Graduate Research Assistant, Dept. of Natural Resources and Environmental Management Mahalo nui loa to our friend and colleague Dr. H.C. Skip Bittenbender for his slack-key version of Manuela Boy. USDA Forest Service, Hawaii Division of Forestry and Wildlife, Forest Health Program Tropical Sub Tropical Agricultural Research TSTAR, USDA CSREES 2006-24135-17697, sponsored by USDA-CSREES
Renewable Resources Extension Act RREA, Project No 13-132, Sponsored by USDA-CSREES This “video log” is a project of the College of Tropical Agriculture and Human Resources, University of Hawai‘i at Mānoa. The editors, authors and publisher intend the information to be reliable but they do not assume any responsibility for consequences of using the information provided. Mention of a company, organization, or agency does not imply recommendation of that source to the exclusion of others that may also be suitable and no endorsement by the publisher or funding agency is implied. It is an amateur production made possible with support from the TSTAR programs of USDA-CSREES.