Responses of Photosynthetic Characteristics to Different Altitudes of Quercus aquifolioides

The leaf photosynthesis and nutrient accumulation of Quercus aquifolioides were studied at different altitudes. The results are as follow: the average leaf areaand specific leaf area of Q. aquifolioides presented the change trend of first increasing and then decreasing with the increase of altitude, reaching the maximum value at 3050 m; the length-width ratio of leaves was significantly lower than other elevations at 2750 m and 3050 m. The instantaneous maximum net photosynthetic rate, transpiration rate, stomatal conductance, and intercellular CO₂ concentration, showed a change pattern of first increasing and then decreasing with the increase of altitude. The contents of C and N per area decreased first and then increased with the increase of altitude, while the content of P per area first increased and then decreased with elevation, and the turning point was all at 3050 m. The photosynthetic nitrogen utilization efficiency and long-term nitrogen utilization efficiency reached their maximum value at 3050 m. The δ¹³C value decreases first and then increases with the increase of altitude, reaching the lowest level at 3050 m and the highest level at 3500 m respectively. In conclusion, it was concluded that the altitude of 3050 m is the most suitable growth area for Q. aquifolioides with the highest photosynthetic efficiency and faster growth. The environment with high altitude inhibited the growth and photosynthetic carbon assimilation while improved the water utilization efficiency of Q. aquifolioides.