Mass and nutrient dynamics of decaying litter fromPassiflora mollissimaand selected native species in a Hawaiian montane rain forest

Abstract

ABSTRACTThe structure and functioning ofAcacia koa-Metrosideros polymorphaforests between 1200 and 1800 m elevation on the island of Hawaii are being threatened byPassiflora mollissima, an aggressive introduced liana from South America. This study was done to evaluate the short-term decomposition dynamics ofPassifloraand selected native leaf and twig litter. The nutrient-rich, non-sclerophyllousPassifloraleaves completely disappeared in less than 5 mo. The estimated time for native leaf litter to lose 95% of initial dry weight ranged from 1.65 y for N-richAcaciaphyllodes to 6.67 y forCibotium glaucum; for woody litter, the time ranged from 4.5 y forAcaciatwigs to 23 y forAcaciabark. Except forCibotiumfrond litter, decay rates were significantly correlated with initial lignin-ash ratios.Passifloralitter did not accelerate decomposition ofAcaciaandMetrosiderosleaf litter.Passiflora, Acacia, andMetrosiderosleaf litter showed net mineralization of N, P, Ca, K, and Mg during the study.Cibotiumfrond litter showed significant accumulation of N, Ca, and Mg; P levels stayed constant and K was rapidly lost. In general, twigs experienced a net loss of most nutrients, while bark experienced either no change or a significant net gain of nutrients. Nutrient cycling has increased inP. mollissimainfested forests.