Effects of prescribed burning on ecological stoichiometric characteristics of carbon， nitrogen and phosphorus in root system of Pinus yunnanensis in central Yunnan Province
[Objective] The effects of prescribed burning on the root system and the ecological stoichiometric characteristics of carbon， nitrogen， and phosphorus in Pinus yunnanensis were investigated in order to provide a scientific basis for determining prescribed burning cycles and root nutrient management in forests. [Methods] The study was conducted in a burned area one year after prescribed burning at Zhaobi Mountain， Xinping County， Yuxi City， Yunnan Province. The root systems of P. yunnanensis were collected from an unburned control plot （UB） and a prescribed burning plot （PB）. Changes in live root biomass （B）， morphological distribution， root organic carbon （ROC）， root total nitrogen （RTN）， root total phosphorus （RTP）， and their ecological stoichiometric characteristics were analyzed. [Results] ① One year after burning， root biomass （B） of P. yunnanensis across different diameter classes ranged from 7.553 to 288.368 g/m2 and was 6.9%—21.5% lower than that in UB within the 0—20 cm soil layer. Fine root biomass density （RBD）， root length density （RLD）， and root surface area density （SAD） decreased by 0.5%—21.5% in the 0—20 cm soil layer one year after burning. In contrast， specific root length （SRL） and specific surface area （SSA） of fine and medium roots increased by 4.1%—21.5% in the same soil layer. ② One year after burning， the ROC， RTN， and RTP contents of fine and medium roots ranged from 335.87 to 492.8 g/kg， 1.934 to 5.724 g/kg， and 0.793 to 1.154 g/kg， respectively. These values increased by 2.19%—38.35% in the 0—10 cm soil layer. The root C∶N （RC∶N） ratios of absorbing and transporting roots ranged from 58.646 to 140.45 g/kg， while root C∶P （RC∶P） ratios ranged from 299.336 to 422.846 g/kg. Both ratios decreased significantly by 29.57%—39.35% in 10—20 cm soil layer （p<0.05）. The root N∶P （RN∶P） ratios across all diameter classes were below 14， suggesting potential N limitation. ③ Correlation analysis revealed that under PB conditions， SRL， SSA， RLD， RTN， RTP， and RN∶P exhibited extremely significant positive correlations （p<0.001）， while B， RBD， ROC， RC∶P， and RC∶N also showed extremely significant positive correlations （p<0.001）. [Conclusion] Following prescribed burning， P. yunnanensis responds to fire disturbance by synergistically enhancing the morphological plasticity of fine roots for efficient nutrient acquisition and increasing the structural support provided by coarse roots， thereby adapting to the post-fire recovery environment through adjustments in both morphological and stoichiometric characteristics.