Global warming induces female cuttings of Populus cathayana to allocate more biomass, C and N to aboveground organs than do male cuttings

Abstract

We investigated differences between the sexes of a dioecious species, Populus cathayana Rehd, in biomass accumulation, biomass allocation, and carbon (C) and nitrogen (N) concentrations under elevated temperature treatments. Cuttings were subjected to three temperature regimes (control, +2°C and +4°C, respectively) in closed-top chambers. Compared with the control treatment, warming significantly increased the net photosynthesis rate, height growth, leaf dry mass, stem dry mass (SM), root dry mass (RM) and total dry mass (TM), and resulted in a higher aboveground : belowground dry mass ratio (AB) in all individuals of both sexes, except in males under the +2°C warming treatment. Furthermore, warming decreased the concentration of C in the stems in both sexes, and increased the concentration of N in the leaves of females, and consequently, resulted in a lower C : N ratio in the leaves of female cuttings than in those of male cuttings. Also, further differences between males and females were detected. In the warming treatments, females exhibited significantly higher values of SM, RM, TM and AB, and lower RM : TM and RM : foliage area ratios than did the males. However, no significant differences in these traits between the two sexes were detected under ambient temperature. Our results indicated that allocation of biomass, and the concentrations of C and N in males and females are greatly affected by an elevated temperature, and that warming benefits females, which accumulate and allocate more biomass to aboveground organs than do the males.