摘要:植物光合生理特性在一定程度上能够体现其对生境的响应情况。通过测定黄土丘陵区安塞国家生态试验站人工纯林和混交林沙棘（Hippophae rhamnoides）、油松（Pinus tabuliformis）和刺槐（Robinia pseudoacacia）在不同水分条件下的光响应曲线，采用5种光响应模型进行拟合分析，以比较3个树种在不同水分条件下适宜的光响应模型及光合生理参数差异，探讨该地区主要造林树种的光合生理生态适应性。结果表明：（1）湿润时期（9月）纯林和混交林中3个树种叶片净光合速率（P_n）均显著高于干旱时期（7月）（P < 0.05），且7月，纯林沙棘、纯林刺槐和混交林刺槐出现光饱和、光抑制现象。（2）5种模型对各树种叶片光响应过程拟合效果的优劣顺序为：直角双曲线修正模型（MRH）、指数修正模型（MEM）、非直角双曲线模型（NRH）、指数模型（EM）、直角双曲线模型（RH）。（3）与9月相比，7月各树种叶片光合生理参数值（表观量子效率[φ]、光补偿点[LCP]、光饱和点[LSP]、暗呼吸速率[R_d]、最大净光合速率[P_nmax]）相对较低，表明在干旱时期，各树种光能利用减弱，光合能力也受到限制。（4）与纯林相比，混交林沙棘光合生理参数值整体呈上升趋势，表明混交造林有助于提高其光合潜力、对弱光的利用能力及光照生态幅宽度；油松整体呈下降趋势，表明混交种植可能会降低其光合作用能力；刺槐变化无明显规律，其叶片φ和P_nmax值下降，R_d增加，光照生态幅最宽，表明混交种植可能会增强其对强光的适应性，但会降低其对弱光的利用能力及光合潜力。



Abstract:The photosynthetic physiological characteristics of plants can reflect their response to environmental conditions. To understand the photosynthetic adaptability of the major tree species for afforestation in a hilly loess region, the light response curves of Hippophae rhamnoides, Pinus tabuliformis, and Robinia pseudoacacia in pure and mixed plantations under different water conditions were measured in Ansai National Ecological Experimental Station, and the data fitted to five models. The results indicated that (1) the P_n values of these three tree species during a wet period (September) were significantly higher than those during a dry period (July) (P < 0.05), and there was photo-inhibition of photosynthesis in the H. rhamnoides pure plantation, R. pseudoacacia pure plantation, and R. pseudoacacia mixed plantation in July; (2) The sequence of fitting effect of the five light response models was, in descending order, as follows:modified rectangular hyperbola, modified exponential, non-rectangular hyperbola, exponential, then rectangular hyperbola. (3) The light response parameters (apparent quantum yield[φ], light compensation point[LCP], light saturation point[LSP], dark respiration rate[R_d], and maximum net photosynthetic rate[P_nmax]) for the three tree species in pure and mixed plantations in July were lower than those in September, suggesting that the light-use capability was diminished, and photosynthetic capacity was inhibited under dry conditions. (4) Compared with the pure forest, the photosynthetic physiological parameters of H. rhamnoides in the mixed forest showed an increased (in general), indicating that mixed afforestation was helpful to improving its photosynthetic potential, light use capability, and the light ecological amplitude. The photosynthetic physiological parameters in P. tabuliformis were reduced (in general), suggesting that mixed afforestation might reduce its photosynthetic capacity. Meanwhile, there was no obvious trend in the photosynthetic physiological parameters in R. pseudoacacia:the values of φ and P_nmax of the leaves decreased, while R_d increased, and the light ecological amplitude was widest, indicating that mixed planting might enhance its adaptability to strong lighting conditions, but it would reduce its ability to utilize the lower levels of light and photosynthetic potential.





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