黄河小浪底库区山地栓皮栎人工林土壤呼吸的季节动态

[目的]分离并量化土壤自养呼吸和异养呼吸,探讨各自贡献率及其随季节变化的动态特征。[方法]采用壕沟法和气体红外分析法,研究黄河小浪底库区山地栓皮栎人工林土壤总呼吸、自养呼吸和异养呼吸速率的季节动态变化、贡献率和环境影响因子。[结果]表明:栓皮栎人工林总土壤呼吸、自养呼吸和异养呼吸均呈夏季速率高、冬季速率低。栓皮栎土壤总呼吸、自养呼吸及异养呼吸速率与5 cm土壤温度均呈极显著指数相关,温度敏感性系数Q_(10)值大小为自养呼吸(3.40)异养呼吸(2.90)土壤总呼吸(2.45);栓皮栎土壤总呼吸、自养呼吸、异养呼吸速率与0 10 cm土壤体积含水量均显著线性相关;土壤总呼吸、自养呼吸速率与0 10 cm土壤电导率显著相关。土壤总呼吸和异养呼吸的温度敏感系数Q_(10)值均在冬季最大,夏秋季最小;而自养呼吸的Q_(10)值则呈相反的变化趋势。栓皮栎人工林自养呼吸和异养呼吸对土壤总呼吸的月贡献率为13.23%37.33%和62.67%86.76%,且自养呼吸的贡献率与土壤温度的季节变化规律相似。土壤总呼吸、异养呼吸与自养呼吸的CO2年通量分别为1 616.41、1 199.39、417.02 g·m~(-2)·a~(-1)。[结论]经过区分与定量化土壤总呼吸及其组分,确定异养呼吸为本研究区栓皮栎人工林土壤总呼吸的主要组分,作用于异养呼吸的生物与非生物因子均能显著影响整个森林生态系统表层CO_2总排放通量的大小,进一步为该研究区森林生态系统碳循环与能量流动的进一步量化研究提供参考。

Seasonal Dynamics of Soil Respiration of Quercus variabilis Plantation in Hilly Area of Xiaolangdi Reservoir of Yellow River

[Objective] To separate and quantify the total, autotrophic and heterotrophic soil respiration. [Method] By the method of infrared gas exchange analyzer in trenching-plot, the total soil respiration (R_S), autotrophic (R_A) and heterotrophic respiration (R_H) in a Quercus variabilis plantation were investigated in hilly area of Xiaolangdi Reservoir of Yellow River. The seasonal dynamics contribution rate and the environmental factors of R_S, R_A, and R_H were determined. [Result] The results showed that the R_S, R_A and R_H varied with the season, the maximum and the minimum were observed at summer and winter, respectively. Significant exponential relationships were obtained between R_S, R_A and R_H and soil temperature at 5 cm (P<0.01). Simultaneously, the temperature sensitivities of R_A, R_H, and R_s, (Q₁₀) were calculated as 3.40, 2.90 and 2.45 respectively. The R_S, R_A and R_H were significantly lined with soil volumetric water content at 0~10 cm (P<0.05). In addition, The R_s and R_A had a linear correlation with soil pore water conductivity at 0~10 cm (P<0.05). The Q₁₀ of R_s and R_H had the highest value in summer and the lowest in winter. Compared with Q₁₀ in R_s and R_H, the seasonal variation in Q₁₀ of R_A presented opposite trend. The estimated contributions of R_A and R_H on R_s were 13.23%~37.33% and 62.67%~86.76%, respectively. The contribution of R_A on R_s was consistent with soil temperature seasonally. In this study, the annual CO₂ flux of R_s, R_H and R_A in the Q. variabilis plantation were 1 616.41, 1 199.39 and 417.02 g·m^-2·a^-1, respectively. [Conclusion] As the main component of total soil respiration, the heterotrophic respiration was significantly correlated with environmental factors, which could influence the overall emission from soil surface and provide theoretical support for further research about carbon cycle and energy exchange in forest ecosystems.