Life history diversity among six species of canopy lianas in an old-growth forest of the eastern Brazilian Amazon
Forest Ecology and Management
Lianas are woody vines that rely on external support for height growth. Although variations among species of lianas in traits ranging from climbing mechanism to stem anatomy have been described little attention has been paid to interspecific differences in life history traits. The objective of this study was to assess the diversity in life history strategies among lianas in an old-growth forest of the eastern Brazilian Amazon. Population size class structure microsite light environment affinity forest successional phase affinity and regeneration mode were assessed and growth and mortality rates were measured over 3 years for six species of lianas: Acacia multipinnata Bauhinia cupreonitans Bauhinia guianensis Croton ascendens Memora schomburgkii and Serjania caracasana.Each of the study species had a free-standing seedling phase prior to the initiation of climbing but the density of free-standing saplings (>=50 cm tall) ranged widely among species from 408 stems ha-1 for B. guianensis to 2 stems ha-1 for A. multipinnata. Species also differed in their propensity for vegetative reiteration of rooted stems; the mean number of climbing ramets per genet ranged from 1.1 for B. guianensis to 7.4 for S. caracasana. Four of the study species (M. schomburgkii S. caracasana and both species of Bauhinia) had the majority of climbing ramets in small diameter classes. However for two of these species (M. schomburgkii and S. caracasana) the size class distributions of the largest stems per genet were flat and unimodal respectively. A. multipinnata and C. ascends had flat size class distributions of both ramets and largest stems per genet.Among the six species there were three apparent patterns of changing association with light environment and forest successional phase over size classes. Two species (M. schomburgkii and B. guianensis) are late successional species. These species were found in all forest phases at relatively low median levels of illumination as seedlings and free-standing saplings more frequently associated with gaps as small diameter climbing stems and in late building and mature phase forest as larger (>=1.5 cm diameter) climbing stems. Three species (B. cupreonitans S. caracasana and A. multipinnata) are early successional species. These species were distinguished from late successional species by occurring in better illuminated and more gap-associated microsites as free-standing saplings and by remaining strongly associated with early building phase forest as large diameter stems. Only C. ascendens is like a pioneer species in being found exclusively in high light microsites in its free-standing stages and associated with gaps or early building phase forest as climbing stems.Median stem diameter growth rates were correlated with successional class ranging from the lowest in late successional species to the highest in the pioneer species. Annual ramet mortality rates differed among species with the lowest rates for the late successional species (1.3 and 4.3% for M. schomburgkii and B. guianensis respectively). Annual genet mortality rates were lower than ramet mortality rates and ranged from 0.2% for M. schomburgkii to 5.5% for C. ascendens. The results suggest that while lianas exhibit a diversity of life history strategies some patterns in liana life history traits for example a positive correlation between stem diameter growth rate and mortality rate may parallel patterns found for trees.