摘要：We explored the relationship between hyperspectral surface reflectance data derived from a handheld spectroradiometer and foliar chlorophyll content of pecans. Canopy scale hyperspectral remotely-sensed data and foliar chlorophyll content determined with SPAD meter were collected simultaneously from two mature pecan orchards for two years. One pecan orchard was located in a clay loam soil and the other in a sandy loam soil. Hyperspectral surface reflectance data were correlated to chlorophyll content. The relationship between remotelysensed data and SPAD was high (R~2≥ 0.8) to moderate (0.8 ≥ R~2 ≥ 0.6) in the first year, and generally weak (R~2 < 0.6) in the second year in both orchards. In the first year, canopy reflectance within the wavelength range 500 to 720 nm of the pecan orchard in the clay loam soil had a moderate to strong relationship (R~2 > 0.6) with SPAD compared to other wavelengths across the canopy reflectance spectrum (i.e. 350-500 and 730-2450 nm). Contour map revealed that the band ratios with a numerator consisting of any wavelength within the 600 to 680 nm range and a denominator of any wavelength along the visible and near infrared spectrum (350 - 1600 nm) had high correlations with SPAD in both orchards in the first year. The vegetation indices NDVI, mNDVI, SIPI, SIPI2 and PSRI also had high regression values (0.91 ≥ R~2 ≥ 0.87) with SPAD in clay loam site and moderate regression (0.73 ≥ R~2 ≥0.67) in sandy loam site in the first year. Overall, canopy surface reflectance data holds promise for studying foliar chlorophyll content in pecan orchards.
