Abstract: In a field experiment, the spectral reflectance, leaf area index (LAI), and aboveground biomass of spring wheat varieties Gaoyuan 602, Longchun 8139 and Dingxi 24 with different planting densities were measured at their different growth stages, and the correlations among the test parameters were analyzed. The results showed that within the range of test wave bands, the maximum value of canopy spectral reflectance was the highest for Gaoyuan 602 and the lowest for Dingxi 24, and the maximum value of leaf spectral reflectance was the highest for Dingxi 24 and the lowest for Gaoyuan 602. The canopy spectral reflectance in visible and mid-infrared wave bands at maturing stage was obviously higher than that at booting stage, while the leaf spectral reflectance in near infrared wave band at booting stage was obviously higher than that at maturing stage. The canopy and leaf spectral reflectance in near infrared wave band increased with increasing planting densities. For the three varieties, there existed “double peak” phenomenon at the red edge of canopy spectra; and from booting to maturing stage, a “blue shift” phenomenon occurred at the red edge. The LAI and aboveground biomass were better correlated to the canopy spectral variables.

Key words: Ecotone between agriculture and animal husbandry, Grassland under protective plantation, Grazing intensity, Grassland quality