Global patterns of tree density are contingent upon local determinants in the world’s natural forests

Previous attempts to quantify tree abundance at global scale have largely neglected the role of local competition in modulating the influence of climate and soils on tree density. Here, we evaluated whether mean tree size in the world’s natural forests alters the effect of global productivity on tree density. In doing so, we gathered a vast set of forest inventories including >3000 sampling plots from 23 well-conserved areas worldwide to encompass (as much as possible) the main forest biomes on Earth. We evidence that latitudinal productivity patterns of tree density become evident as large trees become dominant. Global estimates of tree abundance should, therefore, consider dependencies of latitudinal sources of variability on local biotic influences to avoid underestimating the number of trees on Earth and to properly evaluate the functional and social consequences.

JMG was funded by the Research Commission of the Swiss National Park, Swiss Academy of Sciences SCNAT (project FLUCTREE- 02/2020). J.C. thanks to Spanish Ministerio de Ciencia e Innovación (Project UNIPER, PID2020-114851GA-100). J.B.C. was funded by the Talento fellowships, Comunidad de Madrid (project INOVA-RISK, 2020-T1/AMB-19913). AE thanks the European Social Fund managed by the Regional Government of Madrid (Remedinal TE-CM: S2018/EMT-4338). L.C. and M.J.M. were partly funded through projects CGL2013-45634-P, CGL2016-75414-P, and PID2019-105064GB-I00. L.M. was funded by the Swiss National Science Foundation (PCEFP2_181115) and the Margarita Salas Postdoctoral Fellowship from Universidad de Alcalá (MIU, Spain). A.H. was supported by the Basque Country Government funding support to FisioClimaCO2 (IT1682-22) research group. GBD was funded by the Spanish Ministry of Education (MINEDU; FPU14/05303) and the Regional Government of Madrid (Remedinal TE-CM: S2018/EMT-4338).

Peer reviewed