Effects of prescribed burning on slope runoff and sediment yield in Pinus Yunnanensis forest

Background  Prescribed burning is a management practice that aims to reduce the fire risk. The main objective of this study is to explore the impact of prescribed burning on slope runoff and sediment yield in Pinus yunnanensis forest.

Methods  The runoff and sediment yield were estimated by runoff plots method from May to October in 2020, and the rainfall were obtained self-recording rain gauge (Onset HOBO RG3-M). Base on the observation data from 2 plots established respectively in the burned and unburned forest land in Zhaobi Mountain of Yunnan province, the runoff and sediment yield between burned and unburned forest land were compared via Excel 2010, SPSS26 and Person correlation analysis. And then, the numerical relationship model between rainfall and runoff, sediment yield were built using 1 stopt software.

Results  1) In 2020, the total rainfall in the study area reached 903.2 mm, which was 33.45 mm less than the mean annual rainfall and with approximately 73.64% of rainfall occurring in the rainy season from May to October. 2) After the implementation of the prescribed burning, the runoff and sediment yield significantly increased, the runoff and sediment yield in the prescribed burning plot was 3.01 and 20.92 times as much as that in unburned plot, respectively. 3) Based on the correlation analysis, it was found that runoff yield and sediment yield were significantly correlated with rainfall. 4) The generalized model illustrated that the runoff linear related with the rainfall and rainfall intensity in unburned plots, and the runoff was power function to rainfall and rainfall intensity in burned plots. However, the sediment yields in burned and unburned plots were power function to rainfall, rainfall intensity and runoff in burned and unburned forest land.

Conclusions  Prescribed burning significantly reduced the ability in adjusting on forest hydrological function and increased the amount of soil erosion in P. yunnanensis forest land. However, the erosion modulus in the prescribed burning forest land was much lower than the local allowable soil loss value of 500 t/(km² ·a). This study will provide baseline information for accessing the ecological effects by prescribed burning in forests.