Abstract
Aim Root traits play important roles in plant growth and ecosystem processes. Clarifying the primary drivers of variation in root traits is indispensable for understanding and predicting ecosystem responses to environmental changes. Location China. Taxon Seed plant species. Methods We compiled six key first‐order root traits of 437 seed plant species from different biomes, phylogenetic affiliations, plant growth forms and mycorrhizal types in China. The six root traits included root diameter (RD), root tissue density (RTD), specific root length (SRL), root C content (RCC), root N content (RNC) and root C:N ratio (RCN), which are highly relevant for plant growth rate and resource acquisition. The phylogenetic linear mixed model was employed to examine the effects of climate and soil variables on root traits and to quantify the relative contributions of environment, phylogeny, plant growth form and mycorrhizal type to root trait variation. Results Environment explained most of the variations in RTD and RCC (37.4% and 24.2%, respectively). Mean precipitation of the wettest quarter and mean diurnal temperature range were the main climate drivers of RTD and RCC, respectively. Phylogeny contributed the most to the variation in RD, RNC and RCN (27.0%–52.3%). SRL showed strong links to both environment and phylogeny (35.0% and 27.8%, respectively). However, plant growth form and mycorrhizal type had little effect on root trait variation ( Main conclusions Our study revealed the primary drivers of variations in different root traits of seed plants in China. Climate variability and seasonality variables were more important factors driving root trait variation than the annual averages of temperature and precipitation. Incorporating the different responses of root traits to changing environments and phylogenetic affiliations observed in the present study into terrestrial ecosystem models will improve our ability to predict future vegetation distribution and ecosystem functions under global change.