[Examining vegetation composition and diversity in rocky desertification regions based on the species-area...

Rocky desertification is a major ecological issue in karst regions of China. Scientifically determining the minimum quadrat area for vegetation surveys is crucial for assessing ecological restoration effectiveness. We set up one broad-leaved forest plot and one shrub forest plot in Lechang City, a typical rocky desertification area in nor-thern Guangdong Province. The size of each plot was 100 m×100 m. We conducted community survey and constructed the database of species composition. We used the nested sampling method for secondary sampling statistics of vegetation, and established a species-area curve. The fitting effects of power function, logarithmic function, and logistic model were compared to analyze the relationship between sampling area and species composition and diversity. The results showed that the power function was the best-fitting model (R²>0.996). To include 50%-90% of the species, the minimum required plot areas were 2105-7511 m² for the broad-leaved forest and 2417-7886 m² for the shrub forest, corresponding to side length of 50-90 m. As the area increased, estimated species richness approached the true values more closely, with reduced standard error. Moreover, the relative abundance of dominant species and diversity indices in shrub communities were more sensitive to changes in plot size. For example, the relative abundance of Loropetalum chinense increased markedly from 34% to 54% in the shrubland. The relative abundance of dominant species Castanopsis jucunda in the broad-leaved forest remained stable at around 29% (variation ≤±3%). Given the co-occurrence of vegetation sparsity and patchiness in rocky desertification areas, we recommended that sampling plot size should be rationally set based on community type and research objectives in vegetation surveys to improve sampling representativeness and assessment accuracy.