The variation and correlation among desert plant traits are helpful to understanding the adaptation strategies of plants to the environment and the mechanism of community assembly. However, the diversity and covariation among fine root traits of desert plants and their phylogenetic relationships remain unclear. Principal component analysis, Pearson’s correlations, phylogenetic independent comparison, mixed linear model, and variance decomposition were used to investigate the variation and correlation among 10 fine root traits of 25 common desert plants in arid areas. The results are as follows: (1) We found that all fine root traits varied more among interspecific variation, with the coefficient of variation ranging from 21.83% to 105.79%. Most traits were predominantly shaped by interspecific variation, whereas root phosphorus content (RPC) and intraspecific variation in root carbon/nitrogen ratio (RCN) were more important. (2) Root traits were correlated with four axes of variation. Root nitrogen content (RNC) correlated positively with root diameter (AD) and tissue density (RTD) but negatively with specific root length (SRL), which was inconsistent with the inference of the root economics spectrum (RES). (3) Covariance and trade-off strategies of fine root traits in different life forms of plants were different. Herb RNC was negatively correlated with SRL and positively correlated with AD, while this relationship did not exist in shrubs. Moreover, shrub AD was negatively correlated with RTD, but herbs showed no significant correlation. (4) Influenced by phylogenetic factors, fine root traits exhibited a covariant or trade-off pattern. Taken together, fine root traits were predominantly shaped by interspecific variation, but intraspecific variation also played a significant role. Concurrently, distinct patterns in fine root covariation and trade-off strategies among different life forms of plants were also observed. Future studies should explore the variation and correlation among traits at different scales within and between species from the perspective of life form.

Different organ morphologies determine the manner in which plants acquire resources, and the proportion of biomass of each organ is a critical driving force for organs to function in the future. Regrettably, we still lack a comprehensive understanding of root traits and seedling biomass allocation. Accordingly, we investigated and collected the seedling root morphological traits and biomass allocation of 50 annual ephemeral species to clarify the adaptation to environment. The findings of this study showed that there was a significantly negative correlation between root tissue density (RTD) and root diameter (RD) (p < 0.05), which did not conform to the hypothesis of the one-dimensional root economics spectrum (RES). On this basis, we divided 50 plant species into those rooted in dense or gravelly sand (DGS) or loose sand (LS) groups according to two soil conditions to determine the differences in root strategy and plant strategy between the two groups of plants. Our study revealed that the species rooting DGS tend to adopt a high penetration root strategy. However, the species rooting LS adopt high resource acquisition efficiency. At the whole-plant level, 50 species of ephemerals were distributed along the resource acquisition and conservation axis. Species rooting DGS tend to adopt the conservation strategy of high stem biomass fraction and low resource acquisition efficiency, while species rooting LS tend to adopt the acquisition strategy of high root and leaf biomass fraction and high resource acquisition efficiency. The research results provide a theoretical basis for the restoration and protection of vegetation in desert areas.