The researchers studied the leaf area index (LAI) of mixed spruce-fir-deciduous forests in northeast China. They used digital hemispherical photography to measure LAI and analyzed its spatial variability. The study found that LAI had low variability within and among plots, with values ranging from 1.265 to 4.029. Different models were used to describe the spatial autocorrelation of LAI, with ranges varying from 15 to 155 meters. LAI was negatively correlated with tree diameter and height, but positively correlated with canopy width, density, and species diversity. This research provides insights into estimating LAI in mixed forests of different scales.