Relationships among root traits
Based on the Kaiser’s criterion (Kaiser 1958), data could be condensed in two factors, and the results indicated that the two – first eigenvalue represented 88% of all the variability (Figure 1). After varimax rotation, high root growth correlation for the first factor was observed among TRL, RSA, RV and RT, and they all had positive correlations with the first factor, or with each other respectively. For the second factor, high root growth correlation was observed among root biomass, SRL and RTD, whereas SRL had a negative correlation with the second factor (Figure 1). In brief, there were two response types for assessing root growth of S. breviflora , one was related to root biomass, and another was related to root morphological traits.