The study looked at how adding nitrogen fertilizer affects soil respiration in two types of tree plantations in China. They found that nitrogen fertilization reduced the amount of fine roots in the soil, which in turn decreased soil respiration rates. However, the nitrogen content in the roots and the temperature sensitivity of soil respiration did not change with fertilization. Overall, adding nitrogen fertilizer to these plantations did not affect the nitrogen content in the roots or the temperature sensitivity of soil respiration, but it did decrease the amount of fine roots in the soil, leading to lower soil respiration rates.