ORIGINAL PAPER An invasive tree fern alters soil and plant nutrient dynamics in Hawaii Marian M. Chau • Lawrence R. Walker • Klaus Mehltreter Received: 11 August 2011 / Accepted: 23 July 2012 Ó Springer Science+Business Media B.V. 2012 Abstract Invasive species that alter ecosystems are often successful competitors due to their effects on nutrient cycling. Sphaeropteris cooperi (Cyatheaceae; Australian tree fern) has been invading intact Hawai- ian rainforests for decades and displacing the domi- nant native tree fern Cibotium glaucum (Cibotiaceae). S. cooperi produces more leaves that grow faster, contain more N and P, and decompose faster than C. glaucum leaves. Our experiment tested the effects of additions of leaf litter from native and non-native tree ferns on the growth and nutrient content of four native angiosperm species in forest (N-rich) and landslide (P- rich) soils. Both litter treatments inhibited growth initially in all species, but subsequent responses were species-specific. Compared to control treatments, the increase in biomass was highest in the fast-growing Carex wahuensis and Hibiscus arnottianus with S. cooperi litter in landslide soil. Leaf N in C. wahuensis was higher with S. cooperi litter and in forest soil, as expected, but other leaf nutrient responses showed some evidence of nutrient immobilization from litter addition. Several growth measures were higher with S. cooperi than C. glaucum litter and in forest than landslide soil, suggesting that N availability is the strongest driver of growth. Our results show that S. cooperi can alter nutrient cycling in Hawaiian plants, sometimes with positive effects on growth. However, under natural conditions, native plants must compete for these additional nutrients with S. cooperi and other invasive species. This study contributes to invasion biology as the first to examine the impact of leaf litter of an invasive fern on native species. Keywords Cibotium glaucum Á Competition Á Cyatheaceae Á Leaf litter Á Nitrogen Á Sphaeropteris cooperi Introduction Where tree ferns are abundant in tropical (e.g. Malaysia, Hawaii) and temperate (e.g. New Zealand) forests, they have ecosystem-level effects that are still poorly understood. Tree fern leaves generally have higher N and P and lower Ca than co-occurring seed plants (Richardson et al. 2005; Vitousek et al. 1995). They may acquire these nutrients through litter trapping and channeling of stem flow to their roots (Richardson and Walker 2010). Tree ferns vary in nutrient retention prior to leaf senescence, but their M. M. Chau (&) Á L. R. Walker Á K. Mehltreter Department of Botany, University of Hawaii at Manoa, Honolulu, HI 96822, USA e-mail: mmchau@hawaii.edu L. R. Walker School of Life Sciences, University of Nevada Las Vegas, Las Vegas, NV 89154, USA K. Mehltreter Red de Ecologı ´a Funcional, Instituto de Ecologı ´a, A.C., Xalapa 91070, Veracruz, Mexico 123 Biol Invasions DOI 10.1007/s10530-012-0291-0