Tree, understory, soil, and light data for Hakalau Forest National Wildlife Refuge, Hawaiʻi Island, 2016-2020

This data publication includes tree and shrub basal area, grass biomass, soil nitrogen and carbon pools and fluxes under Acacia koa and Metrosideros polymorpha trees in mid-elevation old pasture sites on Hawaiʻi Island in the Hakalau Forest National Wildlife Refuge from 2016 to 2020. Additional data include grass biomass, soil nitrogen and organic matter, and light levels in experimental understory plantings in Acacia koa forest from nearby sites during the same time period.
These data were collected to better understand the role of forest understory regeneration on soil nutrient dynamics, light levels, and how these factors can lead to tipping points in lowering invasive grass biomass in secondary forests in old pasture sites. Alternative stable equilibrium theory hypothesizes that a system can exist as multiple stable-states under the same environmental conditions. The current state is determined by priority effects and is non-transitory due to the positive feedbacks between the community and the environment. Only when certain thresholds are met do systems experience phase shifts from one stable-state to an alternative. Understanding where these thresholds are is important for restoration and management because it helps managers predict the level of resources needed to push an ecosystem from a degraded state to a more desired condition. We addressed thresholds to soil and light variables that are known to affect native plant regeneration by surveying for these variables under a range of natural and planted understory basal area.
For more information about this study and these data, see D'Antonio et al. (2024).