Short-term changes in the stoichiometric characteristics and spatial distribution patterns of soil elements in Pinus pumila severely burned area

To clarify the response and interaction of soil element content and function at different depths under Pinus pumila forest to severe lightning fire interference, and to provide data reference and theoretical basis for the restoration of Pinus pumila ecosystem after severe lightning fire interference.

The study focused on the soil leaching and deposition layers in the severely lightning damaged area of Pinus pumila in the Greater Khingan Range. The carbon, nitrogen, phosphorus, and trace nutrient content of the soil were measured in the year and year after the fire, and the stoichiometric ratio was calculated. One-way ANOVA, Spearman correlation, and Mantel test were used to calculate differences and correlations; Random forest importance ranking is used to explain the contribution of soil elements to stoichiometry; The partial least squares structural equation model is used to demonstrate the comprehensive effect relationship between soil spatial pattern, recovery time, soil elements, and soil stoichiometry before and after fire disturbance.

The content and stoichiometry of carbon, nitrogen, phosphorus, copper, and mercury in the soil leaching layer and sediment upper layer showed significant responses to fire interference and fire exposure time. Fire interference increased the variability of trace nutrients in the leaching layer, and the changes in soil element content showed a lag with soil depth. The content of trace nutrients in soil is significantly correlated with soil carbon, nitrogen, phosphorus, and their stoichiometric ratios, and they can also significantly explain and predict soil stoichiometric ratios.

Fire interference inhibits the mineralization rate of organic matter in leached soil and increases the availability of phosphorus in soil sediments by high temperature burning and changing the source of substances. The soil element content undergoes significant changes in the short term after fire due to leaching, and lags as the soil layer deepens. Severe fire disturbance weakened the direct effect of soil spatial pattern on soil elements, enhanced the direct effect of recovery time on soil element content, and resulted in significant effects of soil spatial pattern and recovery time on soil stoichiometry.