Functional Traits Of Fine Roots And Their Relationship With Leaf Traits Of 50 Major Species In A Subtropical Forest In Gutianshan

The above- and below-ground processes of ecosystem are closely integrated. As important above- and below-ground plant organs, leaves and fine roots play important roles in photosynthesis and absorbance of nutrients, respectively. While great achievements have been made in recent studies on functional traits of plants, limited data are from below-ground organs and the relationship between above- and below-ground functional traits remains poorly understood. Their structure and function have carried a high degree of differentiation, resulting from the roots in the complex soil environment, making the root system complex in structure and various in function. The previous method of fine root classification by diameter (usually < 2mm) ignores the difference of fine roots between the internal system structure and function. In order to understand the relationships between structure and function of fine roots as well as the relationships between functional traits of roots and leaves, the functional traits of the first five order roots of 50 major species in a subtropical forest in Gutianshan were measured and the correlation between above- and below-ground functional traits were analyzed in this dissertation.Our results showed that there was significant heterogeneity in architecture and element contents among the first five order roots of 50 major species in Gutianshan. This heterogeneity was manifested not only among different root orders of the same species, but also among the same root order of different species. With the increase of root order, root diameter, root length and carbon nitrogen ratio increased, whereas the specific root length, specific surface area, proportion of the counts of each root order, proportion of the cumulative root length of each root order, proportion of cumulative root surface area of each root order and nitrogen concentration decreased for all species. Carbon concentration was at first increased and then decreased, with the third or fourth order holding the maximum value, and tissue density was similar among all root orders.The results of morphology and element contents of fine roots of the first five orders within 4 major families in Gutianshan showed that species in Lauraceae have the smallest root diameter, the longest root length, the lowest specific root length and carbon nitrogen ratio, and the highest nitrogen concentration is for all the five root orders, whereas species in Ericaceae have the largest root diameter, the shortest root length, the highest specific root length and carbon nitrogen ratio, and the lowest nitrogen concentration. No significant differences were found in all root traits except nitrogen concentration between Fagaceae and Theaceae.There is no significant relationship between functional traits of leaves and the first root order roots of 50 common species in subtropical forests in Gutianshan, except the significant correlations in leaf and root nitrogen concentration.Our results indicate that the method of root orders can be used to distinguish the heterogeneous of root system, to explore the general variation of root system of trees. We can further understand the heterogeneous of root system among different families with more studies. Although there is no significant relationship in morphology of leaves and roots, nitrogen concentration between them is highly significantly correlated, providing inspiration for future research on chemical characteristics of fine roots.