Non-structural carbohydrates (NSC) play an important role in yield formation. In this paper, the relationships of NSC accumulation and translocation with yield formation were investigated under elevated CO₂ concentrations ([CO₂]) and nitrogen (N) application rates. A japonica rice (Oryza sativa L.) cultivar, “Nanjing 9108,” was grown at three [CO₂]—Ambient (T0), ambient + 160 μmol·mol⁻¹ (T1), and ambient + 200 μmol·mol⁻¹ (T2)—in open-top chambers (OTC), with three levels of N fertilizer application rates—10 gN·m⁻² (N1), 20 gN·m⁻² (N2), and 30 gN·m⁻² (N3)—Which were set in OTCs using pot experiments. The results showed that the concentration of NSC (C_NSC) and the total mass of NSC stored in stems (TM_NSC) under T1 and T2 were higher than those in the T0 treatment, and the C_NSC and TM_NSC of N3 were lower than those of N1 and N2 at the heading stage. The C_NSC and the TM_NSC were significantly positively correlated with the stem biomass during the growth period and were notably negatively correlated with the N content in leaves (N_leaf) at the heading and filling stages. The seed setting rate was significantly positively related to the apparent transferred mass of NSC from stems to grains (ATM_NSC) at the filling stage, while the relationship between yield and the ATM_NSC was not statistically significant. Although there was no difference in the apparent contribution of transferred NSC to grain yield (AC_NSC) between treatments, NSC stored in stems further accumulated obviously during the late filling stage, implying that the grain yield of “Nanjing 9108” was predominantly sink-limited. We concluded that elevated [CO₂] improved the concentration of NSC at the rice heading stage. The interaction between elevated [CO₂] and N fertilizer rates significantly influenced the concentration of NSC at the filling stage. Rice stems NSC reaccumulated at the late grain filling stage, which implies a restriction on NSC transference to grain.

Background: The introduction of broadleaved tree species in monoculture larch plantations to establish mixed plantations is a feasible way to improve soil properties. However, our understanding of how mixed plantations of larch and broadleaved tree species affect soil properties, particularly microbial community structures and functions, remains limited. We compared three paired monoculture larch (Larix gmelinii) and mixed [L. gmelinii–Fraxinus mandshurica (a dominant broadleaved species)] plantations to investigate the effect of a larch–broadleaved tree species combination on the carbon (C) and nitrogen (N) content, abundance and composition of microbial communities, and enzyme activities associated with litter and soil. Results: The bacterial abundance in the litter, soil N availability, pH and electronic conductivity were significantly higher in the mixed-species plantation in comparison with those of the monoculture plantation. However, in the litter of mixed-species plantation, the relative levels of Agaricomycetes fungi were lower than those of the monoculture plantation, indicating that soil fungal communities were affected more than bacterial communities. In contrast, soil in the mixed-species plantation showed increased exoglucanase and N-acetyl-β-glucosaminidase activities. However, the C and N levels, δ¹³C and δ¹⁵N values, and fungal abundance in litter and soil were not significantly different between the monoculture and mixed-species plantations. Conclusions: Our findings suggest that fungal community compositions and enzyme activities are sensitive to the introduction of broadleaved tree species into larch plantations. Thus, these parameters can be used as important indicators to evaluate the effects of tree species selection on soil restoration.

Effects of elevated CO₂ (E) within a generation on photosynthesis and stomatal features have been well documented in crops; however, long-term responses to gradually elevated CO₂ (E_g) and abruptly elevated CO₂ (E_a) over multiple generations remain scarce. Japonica rice plants grown in open-top chambers were tested in the first generation (F1) under E_a and in the fifth generation (F5) under E_g and E_a, as follows: E_a in F1: ambient CO₂ (A) + 200 μmol mol⁻¹; E_g in F5: an increase of A + 40 μmol mol⁻¹ year⁻¹ until A + 200 μmol mol⁻¹ from 2016 to 2020; E_a in F5: A + 200 μmol mol⁻¹ from 2016 to 2020. For multigenerational tests, the harvested seeds were grown continuously in the following year in the respective CO₂ environments. The responses to E_a in F1 were consistent with the previous consensus, such as the occurrence of photosynthetic acclimation, stimulation of photosynthesis, and downregulation of photosynthetic physiological parameters and stomatal area. In contrast, multigenerational exposure to both E_g and E_a did not induce photosynthetic acclimation, but stimulated greater photosynthesis and had little effect on the photosynthetic physiology and stomatal traits. This suggests that E retained intergenerational effects on photosynthesis and stomatal features and that there were no multigenerational differences in the effects of E_g and E_a. The present study demonstrated that projecting future changes induced by E based on the physiological responses of contemporary plants could be misleading. Thus, responses of plants to large and rapid environmental changes within a generation cannot predict the long-term response of plants to natural environmental changes over multiple generations, especially in annual herbs with short life cycles.