Dominance and rarity in tree communities across the globe: Patterns, predictors and threats
Hordijk I., Bialic-Murphy L., Lauber T., Routh D., Poorter L., Rivers MC., ter Steege H., Liang J., Reich PB., de-Miguel S., Nabuurs GJ., Gamarra JGP., Chen HYH., Zhou M., Wiser SK., Pretzsch H., Paquette A., Picard N., Hérault B., Bastin JF., Alberti G., Abegg M., Adou Yao YC., Almeyda Zambrano AM., Alvarado BV., Alvarez-Davila E., Alvarez-Loayza P., Alves LF., Ammer C., Antón-Fernández C., Araujo-Murakami A., Arroyo L., Avitabile V., Aymard Corredor GA., Baker T., Banki O., Barroso J., Bastian ML., Birigazzi L., Birnbaum P., Bitariho R., Boeckx P., Bongers F., Bouriaud O., Brancalion PHS., Brandl S., Brienen R., Broadbent EN., Bruelheide H., Bussotti F., Gatti RC., Cesar RG., Cesljar G., Chazdon R., Chisholm C., Cienciala E., Clark CJ., Clar DB., Colletta G., Coomes D., Valverde FC., Corral-Rivas JJ., Crim P., Cumming J., Dayanandan S., de Gasper AL., Decuyper M., Derroire G., DeVries B., Djordjevic I., Iêda A., Dourdain A., Dolezal J., Obiang NLE., Enquist B., Eyre T., Fandohan AB., Fayle TM., Ferreira LV., Feldpausch TR., Finér L., Fischer M., Fletcher C., Frizzera L., Gianelle D., Glick HB., Harris D., Hector A., Hemp A., Hengeveld G., Herbohn J., Hillers A., Honorio Coronado EN., Hui C., Cho H., Ibanez T., Jung I., Imai N., Jagodzinski AM., Jaroszewicz B.
Aim: Ecological and anthropogenic factors shift the abundances of dominant and rare tree species within local forest communities, thus affecting species composition and ecosystem functioning. To inform forest and conservation management it is important to understand the drivers of dominance and rarity in local tree communities. We answer the following research questions: (1) What are the patterns of dominance and rarity in tree communities? (2) Which ecological and anthropogenic factors predict these patterns? And (3) what is the extinction risk of locally dominant and rare tree species?. Location: Global. Time period: 1990–2017. Major taxa studied: Trees. Methods: We used 1.2 million forest plots and quantified local tree dominance as the relative plot basal area of the single most dominant species and local rarity as the percentage of species that contribute together to the least 10% of plot basal area. We mapped global community dominance and rarity using machine learning models and evaluated the ecological and anthropogenic predictors with linear models. Extinction risk, for example threatened status, of geographically widespread dominant and rare species was evaluated. Results: Community dominance and rarity show contrasting latitudinal trends, with boreal forests having high levels of dominance and tropical forests having high levels of rarity. Increasing annual precipitation reduces community dominance, probably because precipitation is related to an increase in tree density and richness. Additionally, stand age is positively related to community dominance, due to stem diameter increase of the most dominant species. Surprisingly, we find that locally dominant and rare species, which are geographically widespread in our data, have an equally high rate of elevated extinction due to declining populations through large-scale land degradation. Main conclusions: By linking patterns and predictors of community dominance and rarity to extinction risk, our results suggest that also widespread species should be considered in large-scale management and conservation practices.