Altered fire regimes are one of the most immediate threats to remnant dry forests and shrublands in the tropics. In Hawaii for example, fires were generally infrequent and limited in size prior to human-induced changes in native ecosystems. Over the past century, however, wildfire frequency and size have increased dramatically as a result of invasion by fire-promoting alien grasses. These grasses increase fine fuel loads and alter fuel structure in ways that increase the likelihood of fire ignition and spread. Furthermore, fire effects and post-fire environmental conditions promote recruitment of alien grasses and inhibit recruitment of native woody species. These changes in community structure and composition result in fuel and microclimate conditions that increase the likelihood of subsequent fire. In this way, alien grass invasion initiates a grass/fire cycle that converts native forest to aliendominated grassland. This cycle is now considered the primary agent of forest to grassland conversion in dry and mesic plant communities in Hawaii and elsewhere in the tropics. Tropical dry forest resources in Hawaii and the Pacific are declining at alarming rates. This loss of habitat for threatened and endangered species is leading land managers such as the Department of Defense (DoD) to develop strategies to protect and restore these areas. Native forest rehabilitation and restoration may be the most cost-effective management tool to reduce fuel loads, fire danger, and fire impacts while also controlling invasive species establishment and spread. 

The objectives of this project are to (1) define the current condition and historical changes to tropical dry forest ecosystems in Hawaii, (2) develop technology for regional restoration planning and ecosystem monitoring, (3) quantify restoration potential and develop restoration prescriptions for remnant Hawaiian dry forests and shrublands, and (4) develop effective fuel and fire riskreduction measures that initiate succession of degraded grasslands into native woody communities.

This project will use a suite of newly developed remote sensing technologies and field-based studies to provide concrete, practical information needed for restoration planning and for monitoring threats to the restoration process. Remote sensing methods include analysis of historical aerial photography, high-resolution ecosystem mapping, field validation of remotely sensed data, and web-based satellite monitoring. Field-based methods will address the potential for restoration of native species to alter ecosystem structure in a manner that reduces fine fuels and fire danger. Components of the field studies include addressing the major barriers to restoration— grazing by non-native ungulates, invasion of non-native grasses, lack of native species seed and/or propagules, and absence of suitable microhabitat for native species—in a sequential manner across native community types, and developing and testing the effectiveness of a firebreak design that incorporates traditional fuel breaks grading into “greenstrips” planted with fire-resistant native species.

Results will jointly benefit a number of land management agencies in Hawaii and the Pacific, including DoD and the State of Hawaii Department of Land and Natural Resources. Researchers will work directly with the Pohakuloa Training Area Environmental Crew. Efforts to reduce fine fuel loading through restoration and greenstripping directly support fire management objectives for military training installations in dry forest regions. (Anticipated Project Completion - 2012)