A major study has conducted the first global assessment of palm tree numbers to better understand tropical forest diversity and reduce uncertainty about carbon balance in these ecosystems.

This study, which includedseveral Leeds researchers, surveyed the total numbers of palms in tropical rainforests around theglobe.

Led by Uppsala University (Sweden) and University of Campinas (Brazil), the research reveals that in the Neotropical rainforests such as the Amazon,palms are more than five times more numerous than in comparable Asian andAfrican forests. Many palms were already known to prefer land with a goodgroundwater supply, and the new study confirmed that palm trees were moreplentiful in wetter areas with less fertile soils and shallower groundwater.

Tropical rainforestsare often seen as synonymous with biodiversity. However, this diversity is notevenly distributed, and most plants in a given area belong to only a handful ofspecies. More than half of the total biomass in the Amazon rainforest isdistributed among fewer than 300 tree species including several species of palms.

Palms are among themost common tree species in the Amazon rainforest, but in some tropical areasthey are unusual, or conspicuously absent.Palms are more closely relatedto grasses than to the deciduous trees of the tropics. They therefore differ inmany fundamental ways, in anatomy and physiology, from other tropical trees.

These differences mayhave far-reaching implications when it comes to estimating uptake and storageof carbon in tropical forests, as well as their resilience to climate change.The new study provides knowledge with a vital bearing on further research intoboth of these aspects.

Aerial photo of Quistococha, a Mauritia felxuosapalmswamp close to Iquitos, Peru. Picture: Gabriel Hidalgo

By using large networks of forest plots, the researchers were able to compile a huge database of 2,548 plots and then quantified palm numbers relative to other tree species in the sample plots.The team drew heavily on the networks led by the University of Leeds, particularly RAINFOR, AfriTRON and ForestPlots.net.

Professor Oliver Philips, from Leeds'School of Geography, said:This study shows the exciting potential ofnew, collaborative science that reaches across the world's tropical forests.

We are linking more than 1,000 researchers via plotnetworks and the ForestPlots.net technology developed at Leeds. ForestPlots.netalone includes over 4.5 million tree measurements from more than 15,000different species. The first was made as long ago as 1939, the latest asrecently as last month.

This resource andothers like it combined a huge field effort to reveal the fundamental patternof the tropics' most iconic plants.

Study co-lead author,Bob Muscarella, from Uppsala University, said: To get a better understanding of tropical forests and reduceuncertainty about carbon balance in these ecosystems during climate change, wesummarised data to show how the number of palms vary around the world comparedwith other tree species.

Understanding thedominant species in tropical forests is crucial to recognising how theseforests function and how vulnerable theyre going to be to disturbances andclimate change in the future.

Livistonasaribus in Vietnam. Picture: Nguyen Xuan Hong

Study co-lead author ThaiseEmilio, from the University of Campinas, said: Impressive levels of palm abundance do not come as a surprise to manytropical forest researchers. Days of work may be necessary to measure all thepalms of a single hectare in some places in the middle of Amazon.

However, afair representation of palms in studies of tropical forests functioning is yetto come. Showing where and when palms must be considered is a majorcontribution of our new study.

Further information

Top image credit:Howea forsteriana in Lord Howe Island (Australia). Picture by WilliamJ Baker.

The paperThe Global Abundance of Tree Palms is published inGlobal Ecology and Biogeography 6 July 2020. DOI: 10.1111/geb.13123

For additional information contact University of Leeds press officer Anna Harrison viaa.harrison@leeds.ac.uk

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