In this post, Rebecca Ostertag, Laura Warman, Susan Cordell and Peter Vitousek write about their recent paper “Using plant functional traits to restore Hawaiian rainforest”. You can also watch them in action in the video about their project to see whether hybrid ecosystems could save native forests in Hawaii.

Loosely translated, ‘liko nā pilina’ means “Budding (or growing) new partnerships (or relationships)” in the Hawaiian language. We chose this name for the project because our goal is to create hybrid communities to restore degraded Hawaiian lowland wet forest, using both native and non-invasive, non-native species. In other words, we are creating new forests using some plants which evolved in Hawai’i and others that have come here from around the world. For example, our plots include Hawaiian ōhi’a (Metrosideros polymorpha) and kōpiko (Psychotria hawaiiensis), as well as kukui (Aleurites moluccana, also known as candlenut in Australia) which arrived in Hawai’i with the Polynesians, and mango (Mangifera indica) which is a much more recent arrival (and is originally from India).

Our project is motivated by our past work in lowland Hawaiian rainforests, which are in need of restoration, as they experience low amounts of native species regeneration and exist only in remnant patches filled with highly invasive plant species. It’s a case of ‘dead men standing’: when the existing adults die, this forest will become wholly made up of exotic and invasive species.

Our past experimental work showed that canopy opening is needed for native species regeneration, but that extra light and soil disturbance also stimulates the invasives. Our project is an experimental trial of a new restoration technique. What went into this paper in the Journal of Applied Ecology was a lot of sweat and lab work collecting traits from a variety of candidate species for restoration, but that work is not directly shown here. Instead, we wanted to highlight the general conceptual and statistical approach we used, with hopes that it could be applied more widely. The multivariate methods we described, particularly basing our decisions on the centroid, came after a lot of head scratching and a push to develop a quantitative basis for decision making.

The video shows “the making” of the plots and like most of these efforts. One of the hardest tasks was the initial surveying to make plot boundaries through the very dense vegetation. It took us almost a year to do the clearing, with handpulling and chainsawing. And it took almost that much time to do the planting, because we had to plant species sequentially, when they had grown large enough in the nursery. All of this work was possible only because of the extraordinary teamwork on the project. We had a large team of the PIs, a post-doc, technicians, grad students, undergrad students, interns from abroad and from the US, and many volunteers, including high school and university classes, Hawaiian summer school programs, and other individuals. Working on a new restoration technique in a cultural context excited many of us, and the enthusiasm and hard work of everyone is reflected in the experiment.