Students at Joniskis "Ausros" Gymnasium counted and identified trees within a 200 meter radius of the school, excluding coniferous and deciduous trees. They determined that deciduous trees included oak, birch, linden, willow, and chestnut, while coniferous trees were pine and fir. The students then calculated the amount of oxygen produced annually per hectare by different tree species and determined that oak produces the most at 830 kilograms, making it the best species to cultivate to improve local air quality.