Mixed-stand plantations are not always as beneficial for timber production and carbon sequestration as monoculture plantations. Systematic analyses of mixed-stand forests as potential ideal plantations must consider the physiological-ecological performance of these plantations. This study aimed to determine whether mixed moso bamboo (Phyllostachys pubescens (Pradelle) Mazel ex J. Houz.) and Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) stands exhibited better physiological-ecological performance than monoculture plantations of these species. We analyzed leaf photosynthesis, chlorophyll fluorescence, antioxidant enzyme activities, chlorophyll content and leaf chemistry in a moso bamboo stand, a Chinese fir stand and a mixed stand with both species. The results showed that both species in the mixed stand exhibited significantly higher leaf net photosynthesis rate (Amax), instantaneous carboxylation efficiency (CUE), chlorophyll content, maximum quantum yield of photosynthesis (Fv/Fm), photochemical quenching coefficient (qP), PSII quantum yield [Y(II)], leaf nitrogen content, and antioxidant enzyme activities than those in the monoculture plantations. However, the non-photochemical quenching (NPQ) in Chinese fir and 2-year-old moso bamboo was significantly lower in the mixed stand than in the monocultures. In addition, the water use efficiency (WUE) of Chinese fir was significantly higher in the mixed stand. The results suggest that the increase in leaf net photosynthetic capacity and the improved growth in the mixed stand could be attributed primarily to the (i) more competitive strategies for soil water use, (ii) stronger antioxidant systems, and (iii) higher leaf total nitrogen and chlorophyll contents in the plants. These findings suggest that mixed growth has beneficial effects on the leaf photosynthesis capacity and physiological resistance of moso bamboo and Chinese fir.

The changes of leaf area index (LAI), leaf photosynthetic pigment content, photosynthetic rate of Phyllostachys pubescens in one leaf development cycle (two years) under different fertilization (no fertilization: CK, fertilization at the leave-expansion period: T1, fertilization at the end of August: T2) were studied. The bamboo showed a high LAI potential under T1, which was 14.5% and 23.9% higher than that of T2 and CK, respectively. Fertilization significantly promoted the synthesis of chlorophyll. The average SPAD (soil and plant analyzer development) achieved the highest values under T1, which was 73% and 17.8% higher than that of T2 and CK, respectively. Fertilization caused diurnal changes in photosynthetic rate during the entire leaf development period, and the photosynthetic rate under T1 was significantly higher than that of T2 and CK. The effect of fertilization on photosynthetic rate varied seasonally, especially for T1.

Isoprene is a highly reactive volatile organic compound that significantly affects atmospheric oxidant capacity, regional air quality, and climate change. Moso bamboo (Phyllostachys edulis), a species widely distributed in tropical and subtropical regions, particularly in China, is a strong isoprene emitter with great potential for carbon sequestration. Carbon sequestration is negatively correlated with culm age; however, the effect of this correlation on isoprene emissions remains unknown. In this study, we investigated the photosynthetic and isoprene emission characteristics of Moso bamboo at different culm ages. The results showed that the age effect on isoprene emission was different from that on photosynthesis; the net photosynthesis rate (Pn) was the highest in young, followed by mature, and then old bamboo, whereas the isoprene emission rate (Iso) was the highest in young, followed by old, and then mature bamboo. Moreover, the percentage of carbon loss as isoprene emission (C-loss) during photosynthesis of old bamboo was 35% higher than that of mature bamboo under standard conditions (leaf temperature: 30°C; light intensity: 1000 µmol m-2 s-1). Therefore, we strongly recommend considering the culm age when establishing an isoprene emission model of Moso bamboo. Additionally, because the Iso and C-loss of old bamboo were higher than those of mature bamboo, we suggest that attention should be paid to the management of bamboo age structure and timely felling of aged bamboo to reduce environmental risk.