Impact of environmental factors on canopy hyperspectral characteristics of Camellia oleifera at different growth stages

To investigate the impact of environmental factors on the canopy hyperspectral characteristics of Camellia oleifera at different growth stages, aiming to provide theoretical support for precise fertilization and scientific management of Camellia oleifera plantations and to promote the sustainable development of the Camellia oleifera industry.

A total of 240 Camellia oleifera plants were divided into 12 sample plots within the study area. Canopy hyperspectral data, topographic factors, and soil factors were measured during three key growth periods: spring shoot stage, fruit expansion stage, and full bloom stage. Climate factor data were obtained from the National Earth System Science Data Center. Thirteen vegetation indices were derived from the hyperspectral bands, and a structural equation model (SEM) was constructed to quantify the impact of different environmental factors on canopy spectral characteristics and to reveal their intrinsic relationships and spatial distribution patterns.

The canopy hyperspectral reflectance values of Camellia oleifera during the spring shoot stage, fruit expansion stage, and full bloom stage were 0-0.413, 0-0.532, and 0-0.683, respectively. Significant correlations were found between spectral bands and soil nutrient factors across all periods. The structural equation models (SEMs) constructed with the normalized difference vegetation index (NDVI), photochemical reflectance index (PRI), enhanced vegetation index (EVI), optimized soil-adjusted vegetation index (OSAVI), and plant senescence reflectance index (PSRI) had good fit indices of 0.94, 0.92, 0.83, 0.90, and 0.83, respectively. The results indicated that canopy spectral characteristics of Camellia oleifera are significantly and directly influenced by climate and soil nutrient factors, while topographic factors have an insignificant direct effect but indirectly influence canopy spectra through soil nutrients. Temperature, precipitation, evaporation, nitrogen, and phosphorus were found to have significant impacts on canopy spectral characteristics.

Climate, topography, and soil nutrient factors collectively influence the canopy spectral characteristics of Camellia oleifera, with climate and soil nutrients playing a core role and topography having an indirect effect. This study provides important scientific evidence for large-scale planting and precise management of Camellia oleifera, as well as practical references for improving soil nutrient use efficiency and promoting efficient cultivation techniques.