The researchers studied how much water a poplar plantation in China uses and how it changes with different soil moisture and weather. They used special equipment to measure the water and energy in the air and trees. They found that the plantation used more water when the soil was wet, and less when it was dry. The amount of water used by the trees was influenced by how much sunlight and humidity there was. The methods they used to measure the water were accurate and showed similar results. Overall, the study showed that soil moisture and weather conditions play a big role in how much water trees use.