尕海湿地植被退化过程中土壤碳矿化特征研究

以甘南尕海4种不同退化程度的湿地(未退化(UD)、轻度退化(LD)、中度退化(MD)及重度退化(HD))为研究对象,采用室内5 ℃、15 ℃、25 ℃、35 ℃ 培养法,测定不同土层 SOC 矿化速率和累积矿化量,运用一级动力学方程对土壤的半矿化分解时间(T_1/2)、有机碳矿化潜势(C₀)等参数进行拟合,分析温度、土壤深度和退化程度对土壤碳矿化过程的影响。结果表明：(1)在不同土层、不同温度下,各植被退化程度湿地土壤有机碳 CO₂ 释放量在整个培养期间大致可以分三个阶段,0-4 d快速生成 CO₂ 阶段,4-27 d缓慢生成 CO₂ 阶段,27-41 d平稳阶段；0-10 cm 土层各培养温度下,土壤有机碳矿化速率表现为UD＞LD＞MD＞HD。(2)培养期间,不同退化湿地土壤有机碳矿化速率均随土层加深而降低,表层 0-10 cm的矿化速率(1.14~16.23 mg/(g?d))均显著高于10-20 cm(1.05~2.85 mg/(g?d))和20-40 cm(0.94~1.26 mg/(g?d))土层。(3)整个培养期内,不同退化湿地土壤有机碳总累积矿化量排序为5 ℃(34.54 mg/g)、15 ℃(46.67 mg/g)、25 ℃(58.28 mg/g)和35 ℃(86.46 mg/g)。(4)双库一级动力学方程的C₀值随退化程度增加呈递减趋势,而C₀/SOC随着温度的升高而降低。

Characteristics of soil carbon mineralization in vegetation degradation processin Gahai Wetland

The research took different intensities of vegetation degradation of Gahai wetland (non-degraded (UD), slightly degraded (LD) moderately degraded (MD), and heavily degraded (HD)) on the eastern Qinghai-Tibet Plateau as research objects. SOC mineralization rate and cumulative mineralization of different soil layers were determined within cubation method in lab (5°C, 15°C, 25°C, and 35°C). Using the first-order kinetic equation to fit the parameters of soil semi-mineralization decomposition time (T_1/2) and organic carbon mineralization potential (C₀), and analyzed the effect of temperature, soil depth and degradation degree on soil carbon mineralization. The result showed that: under different soil layers and different temperatures, the soil organic carbon CO₂ emission from wetland soils could be divided into three phases during the whole culture period: the CO₂ rapid growth phase (0-4 d), CO₂ slow growth phase (4-27 d) and steady phase of CO₂ (27-41 d). The order of soil organic carbon mineralization rate was UD>LD>MD>HD at 0-10 cm soil layer of all temperatures. During the cultivation period, the mineralization rate of soil organic carbon in different degraded wetlands decreased with deeper layer. The mineralization rate of surface layer of 0-10cm (1.14~16.23 mg/ (g?d)) were significantly higher than those in 10-20 cm layer (1.05~2.85 mg/(g?d)) and 20-40cm (0.94~1.26 mg/(g?d)) soil layers. The soil carbon mineralization amount in different degraded wetlands were ranked as 5°C (34.54 mg/g), 15°C (46.67 mg/g), and 25°C (58.28 mg/g) and 35°C (86.46 mg/g).The C₀ value of double-base first-order kinetic equation decreased with the degree of degradation, but C₀/SOC decreased with increasing temperature.