The researchers studied plant diversity along a river in China by looking at how many different plant species were found at different altitudes. They found that the number of plant species changed as you went higher or lower in altitude, with the most species found in the middle altitudes. The type of vegetation also changed with altitude. The researchers also found that the diversity of plants was influenced by flooding and the shape of the land at a smaller scale. Overall, the study showed that altitude is important for plant diversity on a large scale, while local factors like flooding and land shape affect diversity on a smaller scale.