Shape of water droplet retained on leaves of Quercus mongolica and Tilia amurense and shape change during evaporation

The shape of droplets on leaf surface (DLS) can not only reflect the leaf wettability and water holding capacity, but also has important significance to understanding the rainfall interception and redistribution of rainfall in the forest. We observed the shape (height, basal area and contact angle) of DLS with 20-100 μL water amount on Quercus mongolica and Tilia amurense leaves and the shape change of 100 μL water drops during evaporation, revealed the shape difference of DLS on these two species and constructed the drop surface model. The result showed that the shape of DLS on T. amurense was relatively flat compared with that on Q. mongolica under the same amount water for separate drops. Namely, the drop on T. amurense leaf surface was 0.15-0.41 mm lower in height, 1.07-9.99 mm2 larger in basal area and 5°-10° smaller in contact angle. By every 1 μL increasing in water amount, the DLS on Q. mongolica and T. amurense increased 0.0125 mm and 0.0091 mm in height, 0.59 mm2 and 0.70 mm2 in basal area and decreased 0.185° and 0.25° in contact angle, respectively. During evaporation, the shape changes of DLS were similar, but the changing rates of height and basal area of DLS on T. amurense were 9.8% and 41.1% faster than that on Q. mongolica respectively, which indicated the dependence of drop evaporation on its shape.