Population dynamics of liana seedlings on Barro Colorado Island, Panama

Background/Question/Methods

Lianas are a common feature of tropical forests, where they are diverse and abundant. There has been a recent burst in the number of articles about liana biology, due to concerns that they are increasing in abundance as a result of climate change. However, so far little is known about the seedling stage of lianas. We studied the diversity and population trends of liana seedlings in the understory of the Barro Colorado Island (BCI) 50-ha Forest Dynamics Plot. First, using data from a long-term census of woody seedlings we assessed population trends in recruitment and mortality not only of liana seedlings, but also of tree and shrub seedlings to compare differences in trends among these plant groups.  We then evaluated the effects of soil nutrients and understory light availability on mortality, recruitment and size transition rates. Finally we evaluated the population trends for two different morphological groups of liana seedling:  free-standing vs. climbing seedlings. 

Results/Conclusions

The liana seedling bank was found to be highly diverse in the BCI 50-ha plot. The overall number of liana seedlings appears to be increasing, based on data from 2001 – 2004 censuses. This net increase in the number of lianas was due to the fact that the mortality rate was consistently smaller than the recruitment of liana seedlings. However, shrub seedlings appear to be increasing at an even higher rate than liana seedlings. Meanwhile, tree seedlings decreased in numbers during the study period. Interestingly, liana species that have support-seeker seedlings seem to be increasing at a faster rate than liana species that have freestanding seedlings. Liana recruitment, mortality and density do not seem to respond strongly to any of the soil nutrients variables or to understory light availability.  The higher recruitment rate of liana seedlings compared to trees, coupled with other studies that have shown that lianas are increasing in numbers and growing faster than trees, can have serious implications for tropical forest dynamics and carbon storage in the near future.