Divergence between ring- and diffuse-porous wood types in broadleaf trees of Changbai Mountains results in substantial differences in hydraulic traits.

Abstract

Hydraulic characteristics of trees are strongly influenced by their xylem structures. The divergence in wood type between ring-porous and diffuse-porous species is expected to lead to significantly different hydraulic architecture between these two functional groups. However, there is a lack of comprehensive comparative studies in hydraulic traits between the two groups, in that no study has compared the whole-shoot level hydraulic conductance and detailed pit-level xylem anatomy has not been reported yet. In the present study, detailed hydraulic related traits were stu-died in three ring-porous and four diffuse-porous tree species commonly found in the broadleaf tree species of the Changbai Mountains, including whole-shoot hydraulic conductance (Kshoot), resis-tance to drought-induced embolism (P50), and detailed tissue- and pit-level anatomical characteristics. Our results showed that: 1) consistent with the differences in stem hydraulic conductivity, ring-porous species showed significantly higher Kshoot but significantly lower resistance to drought-induced embolism, i.e., higher P50, indicating a trade-off between hydraulic efficiency and safety in those two functional groups; 2) consistent with their significant divergence in hydraulic functions, the two functional groups showed significant differences in a suite of xylem anatomical characteristics at both the tissue and pit levels, such as maximum vessel length, vessel diameter, pit aperture area and aperture fraction; 3) significant correlations were identified between xylem structural characteristics and between structure and functions across both functional groups, indicating that differences in hydraulic functions were underlain by divergences in a suite structural traits. The competing structural requirements between different hydraulic traits, such as between shoot hydraulic conductance and resistance to drought-induced embolism, reflected the biophysical constraints of xylem design that could not fulfill multiple requirements of xylem functioning at the same time.