The global biogeography of tree leaf form and habit.
Ma H., Crowther TW., Mo L., Maynard DS., Renner SS., van den Hoogen J., Zou Y., Liang J., de-Miguel S., Nabuurs G-J., Reich PB., Niinemets Ü., Abegg M., Adou Yao YC., Alberti G., Almeyda Zambrano AM., Alvarado BV., Alvarez-Dávila E., Alvarez-Loayza P., Alves LF., Ammer C., Antón-Fernández C., Araujo-Murakami A., Arroyo L., Avitabile V., Aymard GA., Baker TR., Bałazy R., Banki O., Barroso JG., Bastian ML., Bastin J-F., Birigazzi L., Birnbaum P., Bitariho R., Boeckx P., Bongers F., Bouriaud O., Brancalion PHS., Brandl S., Brearley FQ., Brienen R., Broadbent EN., Bruelheide H., Bussotti F., Cazzolla Gatti R., César RG., Cesljar G., Chazdon R., Chen HYH., Chisholm C., Cho H., Cienciala E., Clark C., Clark D., Colletta GD., Coomes DA., Valverde FC., Corral-Rivas JJ., Crim PM., Cumming JR., Dayanandan S., de Gasper AL., Decuyper M., Derroire G., DeVries B., Djordjevic I., Dolezal J., Dourdain A., Engone Obiang NL., Enquist BJ., Eyre TJ., Fandohan AB., Fayle TM., Feldpausch TR., Ferreira LV., Finér L., Fischer M., Fletcher C., Fridman J., Frizzera L., Gamarra JGP., Gianelle D., Glick HB., Harris DJ., Hector A., Hemp A., Hengeveld G., Hérault B., Herbohn JL., Herold M., Hillers A., Honorio Coronado EN., Hui C., Ibanez TT., Amaral I., Imai N., Jagodziński AM., Jaroszewicz B., Johannsen VK., Joly CA., Jucker T., Jung I., Karminov V., Kartawinata K., Kearsley E., Kenfack D., Kennard DK., Kepfer-Rojas S., Keppel G., Khan ML., Killeen TJ., Kim HS., Kitayama K., Köhl M., Korjus H., Kraxner F., Kucher D., Laarmann D., Lang M., Lewis SL., Lu H., Lukina NV., Maitner BS., Malhi Y., Marcon E., Marimon BS., Marimon-Junior BH., Marshall AR., Martin EH., Meave JA., Melo-Cruz O., Mendoza C., Merow C., Monteagudo Mendoza A., Moreno VS., Mukul SA., Mundhenk P., Nava-Miranda MG., Neill D., Neldner VJ., Nevenic RV., Ngugi MR., Niklaus PA., Oleksyn J., Ontikov P., Ortiz-Malavasi E., Pan Y., Paquette A., Parada-Gutierrez A., Parfenova EI., Park M., Parren M., Parthasarathy N., Peri PL., Pfautsch S., Phillips OL., Picard N., Piedade MTF., Piotto D., Pitman NCA., Mendoza-Polo I., Poulsen AD., Poulsen JR., Pretzsch H., Ramirez Arevalo F., Restrepo-Correa Z., Rodeghiero M., Rolim SG., Roopsind A., Rovero F., Rutishauser E., Saikia P., Salas-Eljatib C., Saner P., Schall P., Schelhaas M-J., Schepaschenko D., Scherer-Lorenzen M., Schmid B., Schöngart J., Searle EB., Seben V., Serra-Diaz JM., Sheil D., Shvidenko AZ., Silva-Espejo JE., Silveira M., Singh J., Sist P., Slik F., Sonké B., Souza AF., Miścicki S., Stereńczak KJ., Svenning J-C., Svoboda M., Swanepoel B., Targhetta N., Tchebakova N., Ter Steege H., Thomas R., Tikhonova E., Umunay PM., Usoltsev VA., Valencia R., Valladares F., van der Plas F., Van Do T., van Nuland ME., Vasquez RM., Verbeeck H., Viana H., Vibrans AC., Vieira S., von Gadow K., Wang H-F., Watson JV., Werner GDA., Westerlund B., Wiser SK., Wittmann F., Woell H., Wortel V., Zagt R., Zawiła-Niedźwiecki T., Zhang C., Zhao X., Zhou M., Zhu Z-X., Zo-Bi IC., Zohner CM.
Understanding what controls global leaf type variation in trees is crucial for comprehending their role in terrestrial ecosystems, including carbon, water and nutrient dynamics. Yet our understanding of the factors influencing forest leaf types remains incomplete, leaving us uncertain about the global proportions of needle-leaved, broadleaved, evergreen and deciduous trees. To address these gaps, we conducted a global, ground-sourced assessment of forest leaf-type variation by integrating forest inventory data with comprehensive leaf form (broadleaf vs needle-leaf) and habit (evergreen vs deciduous) records. We found that global variation in leaf habit is primarily driven by isothermality and soil characteristics, while leaf form is predominantly driven by temperature. Given these relationships, we estimate that 38% of global tree individuals are needle-leaved evergreen, 29% are broadleaved evergreen, 27% are broadleaved deciduous and 5% are needle-leaved deciduous. The aboveground biomass distribution among these tree types is approximately 21% (126.4 Gt), 54% (335.7 Gt), 22% (136.2 Gt) and 3% (18.7 Gt), respectively. We further project that, depending on future emissions pathways, 17-34% of forested areas will experience climate conditions by the end of the century that currently support a different forest type, highlighting the intensification of climatic stress on existing forests. By quantifying the distribution of tree leaf types and their corresponding biomass, and identifying regions where climate change will exert greatest pressure on current leaf types, our results can help improve predictions of future terrestrial ecosystem functioning and carbon cycling.