The efficient conservation of vulnerable ecosystems in the face of global change requires a complete understanding of how plant communities respond to various environmental factors. We aim to demonstrate that a combined use of different approaches, traits, and indices representing each of the taxonomic and functional characteristics of plant communities will give complementary information on the factors driving vegetation assembly patterns. We analyzed variation across an environmental gradient in taxonomic and functional composition, richness, and diversity of the herb-layer of a temperate beech-oak forest that was located in northern Spain. We measured species cover and four functional traits: leaf dry matter content (LDMC), specific leaf area (SLA), leaf size, and plant height. We found that light is the most limiting resource influencing herb-layer vegetation. Taxonomic changes in richness are followed by equivalent functional changes in the diversity of leaf size but by opposite responses in the richness of SLA. Each functional index is related to different environmental factors even within a single trait (particularly for LDMC and leaf size). To conclude, each characteristic of a plant community is influenced by different and even contrasting factors or processes. Combining different approaches, traits, and indices simultaneously will help us understand how plant communities work.

Funding provided by: Fundación Caja NavarraCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100006671Award Number: 10833 (Program "Tú Eliges, Tú Decides")Funding provided by: Universidad de NavarraCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100004435Award Number: project "Biodiversity Data Analytics and Environmental Quality"Funding provided by: Universidad de NavarraCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100004435Award Number: project "Red de Observatorios de la Biodiversidad de Navarra (ROBIN)"Funding provided by: Departamento de Educación, Gobierno de NavarraCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100003425Award Number: Ayudas predoctorales para la realización de programas de doctorado de interés para Navarra; Plan de Formación y de I + D 2018Funding provided by: Ministerio Español de Ciencia e Innovación*Crossref Funder Registry ID: Award Number: RyC2020-030647-IFunding provided by: Consejo Superior de Investigaciones CientíficasCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100003339Award Number: PIE-20223AT003Funding provided by: Ministerio Español de Ciencia e Innovación*Crossref Funder Registry ID: Award Number: FJC2020-042954-IFunding provided by: EU "NextGenerationEU/PRTR"*Crossref Funder Registry ID: Award Number: FJC2020-042954-I