期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：43
页码：13267-13271
DOI：10.1073/pnas.1504869112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceTropical forests store nearly 30% of global terrestrial carbon and contribute to 40% of the global terrestrial carbon sink. By affecting tree growth and survival, lianas impact the carbon balance of these forests. Here we demonstrate with a 3-y experiment that lianas substantially reduce forest-level carbon uptake and storage. This study is, to our knowledge, the first direct demonstration of liana effects at the ecosystem scale and illustrates the important role of lianas in tropical forests, particularly with respect to carbon budgets. Lianas are increasing in biomass and productivity throughout the tropics, and thus our findings have even greater relevance in terms of the fate of the tropical carbon balance, as well as for global atmospheric CO2 levels, in a changing climate. Tropical forests store vast quantities of carbon, account for one-third of the carbon fixed by photosynthesis, and are a major sink in the global carbon cycle. Recent evidence suggests that competition between lianas (woody vines) and trees may reduce forest-wide carbon uptake; however, estimates of the impact of lianas on carbon dynamics of tropical forests are crucially lacking. Here we used a large-scale liana removal experiment and found that, at 3 y after liana removal, lianas reduced net above-ground carbon uptake (growth and recruitment minus mortality) by [~]76% per year, mostly by reducing tree growth. The loss of carbon uptake due to liana-induced mortality was four times greater in the control plots in which lianas were present, but high variation among plots prevented a significant difference among the treatments. Lianas altered how aboveground carbon was stored. In forests where lianas were present, the partitioning of forest aboveground net primary production was dominated by leaves (53.2%, compared with 39.2% in liana-free forests) at the expense of woody stems (from 28.9%, compared with 43.9%), resulting in a more rapid return of fixed carbon to the atmosphere. After 3 y of experimental liana removal, our results clearly demonstrate large differences in carbon cycling between forests with and without lianas. Combined with the recently reported increases in liana abundance, these results indicate that lianas are an important and increasing agent of change in the carbon dynamics of tropical forests.
