2.6. Data analysis
This study calculated the average value of root system architecture traits for each species, and the trait values for each species were derived from 10 plant individuals. We calculated the variation coefficient (CV , Standard error divided by average and multiplied by 100%) of each root system architecture trait. Blomberg’s Kvalue is used to test phylogenetic signals of various root system architecture traits(Blomberg et al., 2003). The ReorderData() function in the evobiR package was used to rearrange the root system architecture trait data in the order of the evolutionary tree, and then the phylosig() function in the phytools package in R 4.2.1 was used to calculate the Blomberg’s K value, which was set to 999 times repeatedly (Kraft et al., 2010; Revell, 2012). The pic() function in the ape package was used to calculate the Phylogenetic Independent Contrast (PIC) value of each trait (Felsenstein, 1985; Paradis and Schliep, 2019). The sma() function of the smatr package was used to achieve standardized principal axis (SMA) regression analysis that is used to analyze the correlation between traits. Origin 2021 (Origin Lab Corporation, Northampton, MA, USA) was used to exert data visualization.