Abstract:In order to assess the influence of altitudinal gradients on the spectral reflectance of Pinus koraiensis and Abies nephrolepis which are two dominant conifers in Changbai Mountain, we measured the spectral reflectance of their needles at different altitudinal study sites, using a spectral analysis system in 2008 (Unispec-SC spectral analysis system). Samples were chosen in three altitudinal sites (748 m, 1040 m and 1279 m, respectively) to represent the variability of spectral reflectance in our study. Six trees were selected for each studied species in each study site. Measurements were performed at noon during sunny day. Before we assessed the variation of the spectral reflectance, ordinary methods measuring the pigment contents were adopted to examine the correlations between pigment contents and spectral indices. And spectrophotometer was used to analyze the pigment concentrations. Most of the spectral indices were significantly correlated with pigment concentration at the 0.05 level. We compared the characters of spectral reflectance and spectral indices among study sites. The ratios of spectral reflectance for each wavelength were calculated. Spectral indices for each species, including three indices for chlorophyll and two for carotenoid and two for Car ∶ Chl, were analyzed subsequently. To quantify relationships between spectral reflectance and altitudes, Pearson correlation coefficients were analyzed for altitudinal gradients and specific wavelength. The results showed that there were significant differences in the spectral reflectance among different altitudinal sites. Strong correlations were found between elevation and wavelength in visible and near infrared regions. Spectral indices also showed significant variations with altitude increase. Maybe this means the changes of physiological conditions. The chlorophyll content decreased and the carotenoid content per unit chlorophyll concentration (Car ∶ Chl) increased with the increasing of the altitude. Lower total pigment concentration of P. koraiensis and A. nephrolepis occurred at medium altitudinal site (i.e, 1040 m). Both studied species, P. koraiensis and A. nephrolepis, showed the highest total pigment content at higher altitudinal site (i.e, 1279 m). Significant differences among altitudinal sites were found for every studied species. Strong correlations occurred in most of waveband, although there were obviously differences between two studied species. Chlorophyll indices indicated that the highest chlorophyll content of P. koraiensis and A. nephrolepis occurred in lower altitudinal site (i.e, 748 m). The highest Car ∶ Chl in needles of A. nephrolepis occurred was in medium elevation (1040 m) in broad-leaved Korean pine mixed forest and spruce-fir mixed forest. These indicated P. koraiensis and A. nephrolepis in 748 m confronted lower stress, and A. nephrolepis confronted the highest stress in 1040 m among three gradients. Spectral reflectance curve and spectral indices varied with the elevation. It suggested that the physiological status of P. koraiensis and A. nephrolepis changed. But there was no significant difference in spectral characters between medium elevation (1040 m) and higher elevation (1279 m) in P. koraiensis. This may be attributed to the variations of special character of ecotone. Trees always showed higher chlorophyll concentration in their dominant distribution regions, thus the dominant distribution region of P. koraiensis was probably lower than 1040 m.