氮肥施用对柑橘果园土壤有机碳矿化的影响

土壤有机碳矿化是土壤向大气释放CO₂的最大净输出途径,其与植被的净初级生产力的差值是判断生态系统碳"源"或"汇"的关键。采用室内模拟试验,在10、20、30℃3个温度条件下,研究施肥施用对柑橘果园土壤有机碳矿化的影响。结果表明:3种温度处理下,各施氮处理土壤有机碳矿化速率都表现为培养前期快速下降,培养后期保持相对稳定的趋势。在整个培养过程中,3种温度条件下各施氮处理的土壤CO₂累积排放量为1328.25～2219.42mg/kg,100mg/kg（N4）处理土壤有机碳矿化量最大,CK处理最低,100mg/kg（N4）和80mg/kg（N3）2个高氮处理显著高于低氮50mg/kg（N2）、30mg/kg（N1）处理。土壤有机碳矿化速率随温度升高而增长,不同的土壤施氮条件下土壤有机碳矿化的温度敏感性不同,N₂处理土壤有机碳矿化的温度敏感性最低,N₄处理最高。柑橘果园土壤有机碳矿化受高施氮量影响较大,低施氮影响不明显。随着施氮量的增加土壤有机碳矿化的温度敏感性增加,氮肥施用和温度的共同作用可能使柑橘林向大气中排放的CO₂增加。

Effects of Nitrogen Treatments on the Soil Organic Carbon Mineralization of the Citrus Orchard Soil

Soil organic carbon mineralization was the major pathway of carbon dioxide released from soil into atmosphere. The key point to estimate the carbon source or carbon sequestration of ecosystem was the difference between soil organic carbon mineralization and vegetation net primary productivity. By laboratory simulated experiment, the effects of nitrogen treatments on the soil organic carbon mineralization of the citrus orchard soil were investigated under 10℃, 20℃, 30℃. The results showed that the mineralization rate decreased quickly at the beginning of the experiment but remained stable at the late period under three temperature treatments. The amounts of CO2 ranged from 1328.25-2219.42 mg/kg under three temperature condition, the amount of soil organic carbon mineralization of 100 mg/kg （N4） treatment was the greatest and that of CK was the lowest, meanwhile, The high level nitrogen treatment （N4 and N3） were significant higher than the lower level nitrogen treatment （N2 and Nl）. The soil organic carbon mineralization rate increased with the temperature from 10℃ to 30℃. The dependence of soil carbon mineralization to temperature （Q10） was different under different nitrogen treatments. The Q10 value of N2 treatment was the lowest and that of the N4 treatment was the greatest. The soil organic carbon mineralization in Citrus orange orchard soil was affected significantly by high level nitrogen treatment, but with no significance under lower nitrogen treatment. The dependence of soil carbon mineralization to temperature （Q10） increased with the increasing nitrogen input. Nitrogen combined with temperature may increase there lease of CO2 from Citrus orchard soil.