Abstract: Taking the main afforestation tree species Pinus elliottii, P. massoniana, and Cunninghamia lanceolata in South China as test objects, their needles photosynthetically active radiation (PAR), net photosynthetic rate, and light use efficiency (LUE) at different canopy positions were measured with portable Li-6400 CO₂/H₂O infrared analyzer in July (mid growth period) and October (late growth period). For the  three tree species, their LUE at lower canopies was higher than that at upper canopies in July, but similar with or lower than that at upper canopies in October. North-facing needles had higher LUE than south-facing needles both in July and in October. Overall, the needles and LUE had stronger photosynthetic plasticity to light environment. The LUE of current-year needles was higher than that of one-year old ones. In July, the LUE of current year P. elliottii and P. massoniana needles was higher than that of one-year old ones, and the LUE of different-aged C. lanceolata needles was similar; but in October, the LUE of current-year P. massoniana needles was higher than that of one-year old ones, and the LUE of different-aged P. elliottii and C. lanceolata needles was similar. The photosynthes is of whole canopy was affected by the interaction of light availability and leaf age. It was suggested that forest could assimilate more carbon from atmosphere via adjusting its leaf LUE to adapt the light environment within canopy.

Key words: Tomato, Nitrogen fertilizer, Nutrient uptake, Calcium fertilizer