Task: Question Answering
Input (English): Background Paragraph: In grassland, much of the organic matter added to the soil is from the deep, fibrous, grass root systems. By contrast, tree leaves falling on the forest floor are the principal source of soil organic matter in the forest. Another difference is the frequent occurrence in the grasslands of fires that destroy large amounts of aboveground material but stimulate even greater contributions from roots. Also, the much greater acidity under any forests inhibits the action of certain soil organisms that otherwise would mix much of the surface litter into the mineral soil. As a result, the soils under grasslands generally develop a thicker A horizon with a deeper distribution of organic matter than in comparable soils under forests, which characteristically store most of their organic matter in the forest floor (O horizon) and thin A horizon. 
Story: Two pedologists studied different types of soil. Yun studied forest soils, while Jian studied grassland soil. They were both very surprised with they findings. 
Question: Which scientist read more about the principal source of soil organic matter in the forest?
Output (English): Yun.