Researchers studied how three types of trees in the mountains near Lanzhou City use sunlight and water to grow. They found that the trees' ability to make food through photosynthesis changes throughout the day, with the best time for water efficiency being in the morning. The amount of sunlight and humidity in the air were the most important factors affecting how well the trees could make food and use water. The study suggests that watering the trees during dry seasons can help them stay healthy by keeping the air moist and reducing water loss.