Data from: strawberry guava invasion of a Hawaiian rainforest: changing population pattern

Strawberry guava (waiawī, Psidium cattleyanum O. Deg., Myrtaceae) is a small tree invasive on oceanic islands where it may alter forest ecosystem processes and community structure. To better understand the dynamics of its invasion in Hawaiian rainforests in anticipation of the release of a biocontrol agent, we measured growth and abundance of vertical stems >= 0.5 cm DBH for 16 years (2005-2020) in an intact Metrosideros-Cibotium rainforest on windward Hawai'i Island. Specifically, we compared the growth and abundance of both shoots (originating from seed or from the root mat) and sprouts (originating above ground from established stems) in four replicate study sites. Mean stem density increased from 9562 stems/ha in 2005 to 26,595 stems/ha in 2020, the majority of which were stems < 2 cm DBH. Mean annual rates of population growth (lambda) varied between 1.03 and 1.17. Early in the invasion, both density and per capita recruitment of shoots was greater than that of sprouts, but as overall stem density increased over time, sprout abundance and recruitment came to surpass that of shoots. Relative growth rates among small stems < 2 cm DBH declined over time for both shoots and sprouts, but relative growth rates of sprouts were consistently greater than that of shoots after the first 3 years. The capacity of strawberry guava to recruit from both rooted shoots and vegetative sprouts contributes to the facility with which it can invade intact rainforest, persist in the forest understory, and respond to canopy opening. Strawberry guava thus poses a considerable risk of stand replacement for Hawaiian rainforests. Stand management will require perpetual efforts of guava control at high priority sites as extreme weather events associated with climate change bring canopy-opening events due to storms, drought and pathogens.