Persistence of Native Trees in an Invaded Hawaiian Lowland Wet Forest: Experimental Evaluation of Light and Water Constraints1

摘要

Hawaiian lowland wet forests are heavily invaded and their restoration is most likely to be successful if native species selected for restoration have efficient resource-use traits. We evaluated growth, survival, and ecophysiological responses of four native and four invasive species in a greenhouse experiment that simulated reduced light and water conditions commonly found in invaded field conditions. Our results show that light is a more important limiting resource than water for all species. Specifically, values for photosynthesis, light compensation point, light saturation point, stomatal conductance, leaf mass per area, relative growth rate, and photosynthetic nitrogen use efficiency were all greater under high-light conditions than they were under low-light conditions. In contrast, water limitation negatively affected only stomatal conductance and δ~(13)C. Our results also show that responses to light were species-specific rather than related to whether species were native or nonnative. We also tested restoration potential of top-performing native species under field conditions in a Hawaiian lowland wet forest by comparing relative growth and mortality rates in both invaded (low-light) plots and in plots from which invasive species had been removed (high-light conditions). Of the native species, Myrsine lessertiana and Psychotria hawaiiensis had highest survival and growth rates in low-light plots after 4 yr, and Metrosideros polymorpha showed 100 mortality under the same conditions. Under low light, M. lessertiana and P. hawaiiensis survived and grew at rates similar to those of invasive species in both field and greenhouse and thus represent suitable candidates for restoration in invaded Hawaiian lowland wet forests.