Characterizing variation and association of plant traits is critical for understanding plant adaptation strategies and community-building mechanisms. However, little is known about the variation in leaf traits and the association between traits in desert plants of different life types. We used principal components analysis, Pearson’s correlation, phylogenetic independent contrasts, linear mixed model, and variance decomposition to explore the variation and association of ten leaf traits in 22 desert plants in the arid area. Our results showed that: (1) Interspecific variation in leaf traits contributed more to total variation than intraspecific variation. (2) Intraspecific and interspecific variation in leaf traits were different among different life forms, except for some traits that showed intraspecific variation higher than interspecific in some functional types, other traits with interspecific variation higher than intraspecific variation. (3) Desert plants have a one-dimensional leaf economic spectrum, in which shrubs are a fast acquisitive resource strategy, and herbs are a conservative resource strategy. (4) There were trade-offs between leaf traits, which were influenced by phylogeny. Our results suggest that variation of leaf traits mainly comes from interspecific variation, but intraspecific variation cannot be ignored. In addition, species with different life forms will adopt different ecological strategies to adapt to arid habitats. Therefore, we should study the variation and association of plant traits according to different functional types, in the future.

Characterizing variation and association of plant traits is critical for understanding plant adaptation strategies and community assembly mechanisms. However, little is known about the leaf trait variations of desert plants and their association with different life forms. We used principal component analysis, Pearson's correlation, phylogenetic independent contrasts, linear mixed model, and variance decomposition to explore the variation and association of 10 leaf traits in 22 desert plants in the arid area of northwest China. We found that: (1) the contribution of interspecific variation to the overall variation was greater than the intraspecific variation of all the studied leaf traits; (2) intraspecific and interspecific variation in leaf traits differed among life forms. Some leaf traits, such as tissue density of shrubs and specific leaf area of herbs, exhibited greater intraspecific than interspecific variation, while other traits exhibited the inverse; (3) desert shrubs corroborate the leaf economic spectrum hypothesis and had a fast acquisitive resource strategy, but herbs may not conform to this hypothesis; (4) there were trade-offs between leaf traits, which were mediated by phylogeny. Overall, our results suggest that interspecific variation of leaf traits significantly contributes to the total leaf traits variation in desert plants. However, intraspecific variation should not be overlooked. There are contrasts in the resource acquisition strategies between plants life forms. Our results support understanding of the mechanisms underlying community assembly in arid regions and suggest that future works may focus on the variation and association of plant traits at both intraand interspecific scales.