- Background and aimsRoot traits play a critical role inplant resource-use strategies and ecosystem functioning,but there is great controversy regarding their identityand functionality in different dimensions of below-ground functional variation. Here, we explored the levelof covariation among a suite of key root traits (i.e.specific root length, root dry matter content, diameterand density) as well as between them and two above-ground traits related with plant function (leaf nutrientconcentration and specific leaf area). We also evaluatedwhether these patterns of trait covariation were consis-tent at different spatial scales and organisational levels.MethodsWe collected fine root (< 2 mm) samples of 534individuals (of 80 woody species) along a wide regionalrange of environmental conditions in southern Spain.