Altitudinal variation in the covariation of stomatal traits with leaf functional traits in Changbai Mountain Genetic Variation of Leaf Traits at Different Canopy Positions of Section Aigeiros Clones and Indirect Selection for Growth Leaf Stomatic Characteristics of Dicotyledonous Plants in the Tibetan Plateau Grasslands Relationship between Polycyclic Aromatic Hydrocarbons accumulation and surface structure of leaves in four urban street tree species Effects of temperature increase and grazing on stomatal density and length of four alpine Kobresia meadow species, Qinghai-Tibetan Plateau Stomatal characteristics of ferns and angiosperms and their responses to changing light intensity at different habitats