Variations of leaf nonstructural carbohydrates in an evergreen coniferous species: Needle age and phenology dominate over life history

Abstract

Non-structural carbohydrates (NSCs), including soluble sugar (SS) and starch (ST), are essential for the growth and survival of plants. However, few studies have investigated the effects of phenology, needle age, and life history together on NSCs. We measured NSCs of leaves for 120 Pinus koraiensis individuals of various sizes (0.3–100 cm diameter at breast height, DBH) across needle age and during three leaf development periods to evaluate the effects of phenology, needle age, and life history on NSCs. Concentration ranges were 6.60–12.07, 2.38–8.90 and 10.97–16.18 g·100 g−1 dry mass for SS, ST, and NSC, respectively. Needle age accounted for most of the variations (42.2%-84.4%) of NSCs, followed by phenology (9.2%-46.8%), while life history accounted for only a small proportion. In general, NSC reached its maximum value during the leaf unfolding period and the shift between SS and ST occurred during the leaf fall period. The slope of NSC with phenology generally increased with increasing needle age (absolute value). With increasing needle age, NSC and its components showed gradual upward trends. The slope of NSC with needle age decreased with leaf development (except during the leaf fall period). Life history had significant effects on NSCs in the leaf fall period for both current year and perennial needles, and in the leaf unfolding period only for the current year needles. Needle age significantly affected the correlations of NSC and SS (or ST) only at the leaf unfolding period. Phenology had significant effects on the correlations of NSC and SS (or ST) only for current year needle. Our results clearly showed that the variations of NSC and its components were highly dependent on needle age, followed by phenology. Unexpectedly, the effects of life history on NSCs were much less than those of needle age and phenology. Therefore, needle age and phenology dominate over life history in influencing NSCs, and the ecological significance of NSCs variations need to be reconsidered by effects of incorporating needle age and phenology.