Leaf and root economics space in Fraxinus mandshurica: A test of the multidimensional trait framework within species

Trait-based approaches provide a useful framework for characterising plant strategies and predicting plant performance. However, these approaches have mainly been based on species trait means, thus ignoring the important role of intraspecific trait variation. We measured a suite of leaf and absorptive root traits on individuals of Fraxinus mandshurica in a temperate forest to explore the patterns and drivers of intraspecific trait variation and to evaluate intraspecific trait-performance relationships. Principal component analyses revealed multiple ecological strategies of plants, via variation in leaf and root traits. We found multidimensional covariation in both leaf and absorptive root traits at the intraspecific level. We found no relationship between leaf and root trait dimensions. Root trait dimensions were mainly influenced by environmental conditions, whereas leaf trait dimensions were mainly influenced by tree size. Absorptive root traits are better predictors of tree performance than leaf traits. We also found that the trait-performance relationship varied with tree size. Synthesis. Overall, our study emphasises the necessity to pay attention to intraspecific trait variation and correlation and contributes to a comprehensive understanding of how plants respond to multiple abiotic and biotic drivers. Additionally, we highlight the need to combine above- and below-ground traits to improve predictions of plant performance and hence predictions of forest dynamics and ecosystem functions.