We know that trees are nature’s purifier (净化器): They absorb carbon emissions (碳排放) and release oxygen. But their ability to do that changes as they age. According to Newsweek, trees that are at least 20 years old can absorb carbon better than younger ones and older ones. And a recent study by researchers from South Korea’s Forest Research Institute has found exactly how much carbon that each 25-year-old cherry tree can absorb: 20 pounds (9.1 kilograms) each year.