Effects of prescribed burning on species diversity of understory in Pinus yunnanensis forests of southwest China

Abstract Background The Pinus yunnanensis forest in southwestern China is a unique and significant vegetation type. However, it is susceptible to frequent fires. To mitigate the risk of hazardous fires, prescribed burning has often been employed in these forests. Nevertheless, it is important to consider the potential impact of prescribed burning on the structure of plant communities and species diversity in Pinus yunnanensis forests. To investigate the specific changes in plant community characteristics of caused by prescribed burning, a study was conducted in the Pinus yunnanensis forest located in Zhaobi Hill, Xinping county. Results Prescribed burning has had minimal effects on canopy trees, but has partially altered the characteristics of the understory community. It has decreased the number of shrub species from 26 to 19, with a shift in dominance from saplings of Lithocarpus mairei and Pinus yunnanensis in the unburned area to Duhaldea cappa and Craibiodendron stellatum in the burned area. Additionally, prescribed burning has partially altered the abundance of species and reduced the average height of shrubs. Furthermore, prescribed burning has increased the number of herb species from 27 to 40, but has had minimal impact on their abundance, height, and importance value. It is worth noting that prescribed burning has different impacts on the species diversity of shrubs and herbs. It significantly decreases the α species diversity of shrubs, but only has minimal effects on the α species diversity indices of herbs. The β diversity indices indicate that the species composition in both burned and unburned areas is similar, but the impact of prescribed burning on shrubs is greater than on herbs. Overall, prescribed burning appears to be the primary factor affecting the species diversity index of shrubs, while altitude, forest structure, and soil nutrient content exert greater influences on the species diversity index of the herbaceous layer. Conclusions Prescribed burning had little impacts on overstory trees of the Pinus yunnanensis forest, it had slightly positive effects on the height of herbs, and increased species richness of herbs from 27 to 40. However, the effects of prescribed burning on the species diversity and the height of shrub layers were significant and negative. Prescribed burning was the dominant factor shaping the community structure and species diversity of the shrub layer, and the missing saplings of trees in shrub layers might influence future forest succession in a long time.