Spectral reflectance response of Fraxinus mandshurica leaves to above- and below ground competition

摘要

The responses of leaf spectral reflectance of Fraxinus mandshurica saplings to above- and belowground competition were studied under field conditions in a temperate forest near the Changbai Mountain Nature Reserve in northeast China. Two sets of four treatments, each inducing different levels of competition, were applied under the shade of the forest canopy and in a clear felling area under full light exposure. The heights of the saplings were measured once a month and leaf reflectance was measured at the same time. At the end of the experiment, all target saplings were excavated, and their biomass and root morphological traits were analysed. All these traits were then compared with the leaf spectral reflectance values and different spectral indices. We found that changes in height and biomass were significantly affected by the treatment and site, and that the differences between the four treatments coincided well with the differences in the spectral indices. The final biomass and all root morphological attributes were significantly affected by the treatment and site. Again, these differences corresponded well with the differences in the spectral indices and the spectral reflectance curves. In conclusion, we found that leaf spectral reflectance was sensitive to competition and showed a close relation with other responses, which makes it a reliable indicator of the response of F. mandshurica to varying competition intensities, especially when competition is very severe.