关键词: 九龙山, 封育植被, 物种多样性

Abstract: Field experiments were carried out to examine the effects of different soil nitrogen and phosphorus concentrations on leaf nitrogen and phosphorus concentrations and photosynthesis of tamarind (Tamarindus indica L.) in the Yuanjiang and Yuanmou dry-hot valleys. Soil nitrogen and phosphorus concentrations, leaf nitrogen and phosphorus concentrations, and the photosynthetic parameters were measured. We used four kinds of common light response curve fitting models, including rectangular hyperbola model, non-rectangular hyperbola model, modified rectangular hyperbola model, and quadratic regression model. The results showed that soil nitrogen and phosphorus concentrations, and ratio of nitrogen to phosphorus were significantly different between Yuanjiang and Yuanmou dry-hot valleys. Soil nitrogen concentrations were 1.205 and 0.881 g·kg^-1, soil phosphorus concentrations were 0.481 and 0.177 g·kg^-1, soil nitrogen to phosphorus ratios were 2.61 and 5.49, respectively in Yuanjing and Yuanmou dry-hot valleys. Leaf nitrogen concentrations of tamarinds were 17.28 and 13.51 g·kg^-1 in Yuanjing and Yuanmou dry-hot valleys, respectively, being significantly different. There was no significant difference in leaf phosphorus concentrations (1.51 vs. 1.81 g·kg^-1) between Yuanjiang and Yuanmou valleys. The ratio of nitrogen to phosphorus in leaf had no significant difference between the two sites (11.80 vs. 11.66). The four light response curve fitting models all had a high degree of fitting for the light response curves of the tamarind in the two sites. The modified rectangular hyperbola model under the condition of low photosynthetically active radiation (PAR) was the best one, while the quadratic regression model under the condition of high PAR fitting degree was the most suitable model. The apparent quantum efficiency (α), light compensation point (LCP), dark respiration rate (R_d) were calculated with the modified rectangular hyperbola model, with corresponding values of 0.055, 38.921 μmol·m^-2·s^-1 and 1.377 μmol·m^-2·s^-1 in Yuanjiang valley, and 0.060, 8.019 μmol·m^-2·s^-1 and 0.404 μmol·m^-2·s^-1 in Yuanmou valley, respectively. The maximum net photosynthetic rate (P_nmax) and light saturation point (LSP) were calculated with the quadratic regression model, with corresponding values of 11.073  and 3223.2 μmol CO_2·m^-2·s^-1 in Yuanjiang valley, and 6.331  and 2532.4 μmol CO₂·m^-2·s^-1 in Yuanmou valley, respectively. In conclusion, photosynthetic rate of tamarind in Yuanjiang dry-hot valley was significantly higher than that in Yuanmou dry-hot valley. Soil phosphorus and leaf phosphorus concentrations were the key influencing factors for the photosynthesis of tamarind.