Changes in Leaf Spectral Reflectance and Photosynthetic Characteristics with Tree Height in Three Tree Species

As tree grows high,leaves in the top are always affected by water transport resistance,which leads to water deficiency.Accordingly,the biological characteristics of leaves also change.In this paper,3 tree species(Quercus mongolica,Tilia amurensis,and Pinus koraiensis) were observed to study the relationship between leaf spectral reflectance(spectral reflectance R,photochemical reflectance index PRI) and photosynthetic characteristics(photosynthetic rate Pn,transpiration ratio Tr and stomata conductance Cond) with different tree height.The results showed that PRI and photosynthesis in Q.mongolica and T.amurensis had a trend of increasing at the first and decreasing later with tree height.Their variations were significant at different heights(P0.05).In contrast,these indexes of P.koraiensis showed constant increase with tree height.The results indicated that water deficit affected more intensely the leaf photosynthesis in the top of the first 2 tree species than P.koraiensis,probably because of different stomatal regulation mechanism.Additionally,there was a significantly positive relationship between leaf PRI and Pn in Q.mongolica and T.amurensis(r2=0.986,0.890).However,PRI could not reveal the changes of Pn in P.koraiensis,which suggested that PRI should be used in combination with species difference.