The study looked at how different levels of nitrogen, CO2 concentration, and temperature affect the chlorophyll content in Quercus mongolica Fisch. seedlings. They found that high nitrogen levels increased chlorophyll content, with CO2 concentration and temperature having varying effects depending on the nitrogen level. Under high nitrogen, CO2 accelerated chlorophyll a and b components, while elevated temperature increased chlorophyll a but not b. Normal nitrogen levels showed no significant changes in chlorophyll content with CO2 or temperature. Seedlings without nitrogen added showed some improvement in chlorophyll a with CO2 and temperature, but not in chlorophyll b. Overall, elevated CO2 concentration increased the need for nitrogen in the seedlings, with elevated temperature also requiring more nitrogen to some extent.