Leaf traits of Chinese fir (Cunninghamia lanceolata) do not support the well-accepted ‘flux trait network’ hypothesis

Abstract

Widely-accepted universal models and hypotheses such as ‘high vein density -faster growth and higher productivity’ hold that high leaf vein density may promote higher coupling efficiency of carbon and water, indicating rapid individual growth and high stand productivity, have attracted huge interest. However, these models and hypotheses did not include enough gymnosperm samples especially conifers cultivated in subtropics. We here examined the value and scaling relationships between leaf vein density and leaf functional traits sampled from center region of the distribution range of Cunninghamia lanceolate, which has been well known for rapid growth. We also retrieved an empirical dataset that included photosynthetic, biochemical, anatomical and hydraulic traits of C. lanceolata. The leaf vein density (range 0.34 to 1.09 mm mm -2) is extremely low compared to the reported global range (1 to 25 mm mm -2), while C. lanceolata is famous for both fast-growing and high-yielding in China for a long time. We further verify that higher vein densities are associated with smaller leaves (r=－0.71, p<0.001), which is consistent with that found in angiosperms. However, we found that vein density – thickness correlations and leaf lifespan plasticity showing opposite trends for C. lanceolate (negative) as compared with global species (positive), and such relationships may indicate the tradeoffs between functional efficiency and productivities. Our results would provide an effective complementary assessment of general growth rules, including evaluation of the influence of regional plant trait characterization, configuration of plant species and traits efficiency for hydraulic potential.