Carbon Sink Capacity and Health Assessment of Pinus tabuliformis and Quercus aliena var. acuteserrata Forests in the Huoditang Forest Area of the Qinling Mountains

Focusing on the Pinus tabuliformis and Quercus aliena var. acuteserrata forests in the Huoditang Forest Region of the Qinling Mountains, the biomass of the tree layer was calculated through plot surveys and existing biomass regression models. Meanwhile, the biomass of the shrub layer and herb layer was determined through the average standard tree method and quadrat harvesting. At the same time, the respiration rates of the soil and different decay classes of logs were measured, and the total amount of carbon emissions were calculated by summing up the values, in order to evaluate the carbon sink increment and carbon budget characteristics of the P. tabuliformis and Q. aliena var. acuteserrata forests. In addition, the Analytic Hierarchy Process (AHP), entropy weight method and game theory were applied to construct a forest health evaluation system suitable for the region. The health index was then calculated by the comprehensive index method. The results showed that: The carbon density of the vegetation layer in both forest types exhibited an increasing trend, and the carbon density in the Q. aliena var. acuteserrata forest (49.39 ± 4.12) t/hm^-2 was significantly higher than that in the P. tabuliformis forest (39.31 ± 3.25) t/hm^-2. The total amounts of CO₂ released from the P. tabuliformis forest and the Q. aliena var. acuteserrata forest were 35.71 t/hm^-2 and 39.50 t/hm^-2, respectively. Soil respiration was the main source of carbon emissions, accounting for more than 90% of the total. The annual net CO₂ uptake of the P. tabuliformis and Q. aliena var. acuteserrata forests was 3.60 t/hm⁻² and 9.89 t/hm⁻², respectively, and both forests functioned as carbon sinks. The proportion of healthy and healthier in sample plots of the P. tabuliformis and Q. aliena var. acuteserrata forests was 33.3%, and the overall health status was good. The health index of the P. tabuliformis forest (0.491) was slightly higher than that of the Q. aliena var. acuteserrata forest (0.479).