黄土高原森林草原区6种植物光合特性研究

 对黄土高原森林草原区6种不同植物的生理生态学特性进行了一个生长季的野外观测。测定了2002年生长季早、中、晚期植物叶片的光合、蒸腾速率及相应的微气象因子和土壤水分的含量。在此基础上，采用机理性生理生态学模型对黄土高原森林草原区6种植物净光合速率和气孔导度与环境因子的关系进行了分析，净光合速率模型和气孔导度模型分别能够解释57%～79% 和40%～59% 生长季中净光合速率和气孔导度的日变化。在此基础上根据拟合得到的参数计算了典型7月份天气的净光合速率的日变化。模拟的结果表明：沙棘(Hippophae rhamnoides L. subsp. sinensis Rousi)的生物化学光合能力最强，茵陈蒿（Artemisia capillaris）的光呼吸速率最低，这两种植物的净光合速率高于其它植物种。刺槐（Robinia pseudoacacia）、铁杆蒿 (Artemisia gmelinii)、茵陈蒿和沙棘在午后出现的净光合速率下降主要是由气孔导度减小引起的，而苹果 (Malus pumila) 和柠条 (Caragana korshinskii)午后净光合速率的降低与叶肉细胞酶的活性降低有关。这些结论为未来的实验室测定提供了野外观测佐证。

PHOTOSYNTHETIC CHARACTERISTICS OF SIX PLANT SPECIES IN A FOREST STEPPE OF THE LOESS PLATEAU, CHINA

Diurnal net photosynthetic and transpiration rates of six plant species on the Loess Plateau were measured in the field during May, July, and September 2002. Photosynthetic characteristics of these species were quantified by applying a model of net photosynthesis and stomatal conductance to the field data. The results indicated that the model could explain up to 79% and 59% of the variation in the net photosynthetic rate and stomatal conductance, respectively. Hippophae rhamnoides and Artemisia capillaris had higher net photosynthetic rates than the other species because these species had high biochemical photosynthetic efficiencies whereas the other species had low photorespiration coefficients. An afternoon depression in photosynthetic rates in Robinia pseudoacacia, Hippophae rhamnoides L. subsp. sinensis Rousi, Artemisia gmelinii and A. capillaris was explained by decreased stomatal conductance, and, in Malus pumila and Caragana korshinskii, the reduction was due to decreased biochemical photosynthetic capacity. These field results provide a basis for future laboratory studies to better understand the ecophysiological properties of these plants.