Objective This paper examines allometry relationship of branches and leaves of typical desert shrub species in the Tarim Basin, Xinjiang of northwestern China, aiming to reveal their morphological and structural adaptation strategies.
Method During July−August 2023, we investigated three shrub species (Lycium ruthenicum, Nitraria sphaerocarpa, N. tangutorum), which had assimilative branches, and four shrub species (Tamarix hispida, T. ramosissima, T. tarimensis, T. taklamakanensis), which did not have assimilative branches. We used the standardized major axis regression analysis (SMA) to examine the allometry relationship among leaves, branches, and branch-leaf traits, with a particular focus on testing differences in allometric scaling exponent (b) between the two functional groups and among species.
Result (1) The relationship between leaf area and leaf dry mass growth showed no significant differences between groups and species, with all showing isometric growth. (2) The relationship between branch volume and dry mass showed significant differences among groups and between species with and without assimilating branches. Groups with assimilating branches exhibited higher b values. However, no significant difference in b was found among species with assimilating branches, with a common value of 1.125, indicating that branch volume increased significantly faster than branch dry mass. (3) There was no significant difference in length and diameter of desert shrub branches between groups and species, with b consistently estimated at 1.490. The growth rate of branch length was significantly faster than that of branch diameter. (4) Overall, branch dry mass grew significantly faster than leaf dry mass (b = 0.876) for desert shrubs, although some species (N. sphaerocarpa and T. taklamakanensis) exhibited isometric growth, while there was no significant correlation between leaf dry mass and branch dry mass for T. tarimensis.
Conclusion The allometry relationship of leaf area-leaf dry mass, branch length-branch diameter, and leaf dry mass-branch dry mass are not influenced by morphology of photosynthetic organs. However, the allometry relationship between branch volume and branch dry mass differs significantly between functional groups based on the presence or absence of assimilative branches. These findings highlight both convergent and divergent morphological and structural adaptations of desert shrubs in response to their environment. The research results have deepened our understanding of growth patterns and environmental adaptation mechanisms of desert plants, providing a scientific basis for vegetation ecological construction in desert areas.
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