Relationships among Leaf, Stem and Root Traits of the Dominant Shrubs from Four Vegetation Zones in Shaanxi Province, China

Leaves, stems and roots as the main plant organs have specific functions and together modulate survival, growth and reproduction. The relationships between these organs are high research priority, and there have been many hypotheses about the trade-offs between them. However, the results of these hypotheses are inconsistent and confusing. In this study, we examined 15 core traits of leaves, stems and woody roots of 27 dominant shrub species and further tested the hypotheses about the relationships between these organs. Measurements were made for shrubs across 9 sites including desert, steppe, temperate forest and subtropical forest in Shaanxi Province of China. Many significant correlations of different organ traits were found, e.g. nitrogen and phosphorus content showed a significant positive correlation, either within or across organs. Also, representatives of structural traits (carbon content and dry matter content) and mineral nutrient traits (nitrogen and phosphorus content) showed significant positive correlations among the leaves, stems and roots. The results of this study supported the hypotheses that there were significant correlations between leaf and root and between stem and root. Similarly, we found that trade-off between leaf and stem-plus-root showed a significant correlation. Thus, root traits, which are difficult to measure, are coordinated with those of the leaf and stem. We conclude that the leaf component of shrubs is a good proxy for the whole-plant in studying trade-offs and it could provide a convenient way to understand the whole-plant economic spectrum by focusing on the leaf economic spectrum.