EVALUATING PRODUCTION AND NUTRIENT CYCLING OF GRAZING MANAGEMENT SYSTEMS IN HAWAIIAN FORESTS AND RANGELANDS

The extensive clearing of forests for crops (sugarcane, pineapple, and others) and livestock grazing has significantly altered native ecosystems throughout the Hawaiian Islands. These drastic changes in vegetation community composition have decreased species richness, reduced habitat for native birds and understory plant species, and altered nutrient cycling. Historically these intensive cropping systems and poor livestock management have compounded the consequences of deforestation resulting in degraded soils and the proliferation of weedy species. Now, much of the acreage formerly devoted to sugar and pineapple production lies either fallow, slowly transitioning into non-native and unmanaged forested areas with undesirable woody species or are being utilized for livestock production on whatever volunteer forages that have become established (Deenik et al. 2007). Currently, these lands, with their proliferation of weedy trees, shrubs, and grasses, provide little to the production of food and fiber for the state but pose a significant wildfire threat to urban areas (Trauernicht 2019) and contribute to the silting of near-shore coastal zones and coral reefs from soil erosion (Dawson 1999, Takesue and Storlazzi 2017).The development of silvopasture systems in abandoned croplands and livestock pasture has significant potential in Hawaii to at once, maintain the production of food and fiber from these lands while enhancing ecosystem services linked to improved carbon capture and nutrient cycling, and reducing soil erosion, weed encroachment, and wildfires. Unique challenges exist in Hawaii that create barriers to utilizing silvopasture systems. These include the cost of establishment, labor, and not insignificantly, the lack of knowledge and information on establishment, management, and economics specific to Hawaii. Foresters, who are often employed to develop and manage silvopasture systems, lack specific training and knowledge of sound grazing management and animal husbandry practices. Likewise, livestock producers lack experience and training in establishment of trees for silvopasture systems.Livestock production is a vital component of Hawaiian agriculture and can be used as an important tool in the reforestation of former croplands in a silvopasture setting. This research proposal will evaluate grazing management strategies in both previously forested crop (sugarcane and pineapple) and grasslands and silvopastures to identify systems that improve plant community composition, ecosystem functions, and reduces the threat of wildfire.The results of this project will provide a basis for integrating grazing practices with forest restoration and silvopasture establishment and management. This project will provide information to aid ranchers in making ecologically sound, economically feasible management decisions regarding livestock production in Hawaii. Data collected will also provide a baseline for future scientific exploration of the subject, as these aspects of investigation are surprisingly lacking in the literature, particularly in a Hawaiian context.The utilization of livestock grazing in forest restoration and in the management of silvopasture systems requires a thorough knowledge of grazing management strategies and animal husbandry skills to prevent unintended damage to the trees being grown and improve ecosystem structure and function. There is a lack of experience and knowledge in the establishment and management of silvopasture in Hawaii as well as misguided impressions about the utility of livestock grazing as a tool to manage understory vegetation in reforestation efforts. Compounding this is the fact that there is very little literature on the establishment and management of grazing in forested lands and silvopasture systems, particularly with a Hawaiian context. The goal of this project is to evaluate the suitability of livestock grazing management strategies to restore ecosystem structure and function of former forested lands and silvopasture systems in Hawaii. Experiments will be conducted in the field.Our specific objectives are to:Determine the effects of grazing frequency and intensity on the quantity and quality of forage and plant community composition, ecosystem carbon and nutrient cyclinig, and oveall soil health parameters in previously forested crop and rangeland and silvopasture systems in Hawaii.Evaluate the use of multi-species (cattle, sheep and/or goats) grazing strategies to manage tropical silvopasture and previously forested rangelands in Hawaii for improved ecosystem carbon capture, nutrient cycling, and overall soil health, andUse the process-based ecosystem model, Daycent, to evaluate long-term effects of tropical silvopasture systems on ecosystem carbon, nutrient cycling, and overall soil health parameters.