【摘要】 采用室内培养方法,研究不同温度(15℃、25℃和35℃)条件下红壤性水稻土不同粒级团聚体(>2 mm、1～2 mm、 0.25～1 mm、0.053～0.25 mm和<0.053 mm)中有机碳矿化特征,分析团聚体有机碳矿化对全土有机碳矿化的贡献并探讨团聚体有机碳矿化的温度敏感性。结果表明:>0.25 mm大团聚体较<0.25 mm微团聚体含有更多的有机碳和全氮,碳氮比随团聚体粒级减小而降低。全土和各粒级团聚体有机碳矿化速率在培养的前7d快速下降,之后缓慢降低并在培养后期趋于稳定。25℃和35℃培养时,有机碳累积矿化量在>1 mm团聚体中最高,在0.053～0.25 mm团聚体中最低,且有机碳累积矿化量与有机碳和全氮含量显著或极显著正相关。>2 mm和0.25～1 mm团聚体对全土有机碳矿化的贡献最大,贡献率分别为34.6%和28.8%。培养温度的升高显著提高了全土和团聚体的有机碳矿化速率、累积矿化量和矿化率。不同粒级团聚体有机碳矿化的温度敏感性系数为1.38～2.00,与有机碳、全氮和碳氮比均极显著正相关。综上所述,>0.25 mm大团聚体在红壤性水稻土有机碳矿化中发挥主导作用,升温促进了不同粒级团聚体有机碳的矿化,团聚体有机碳矿化的温度敏感性与有机质的数量和质量密切相关。更多还原

【Abstract】 【Objective】 Soil organic carbon(C) is distributed heterogeneously in soil aggregates of all size particles.Organic C mineralization is an important biochemical process in the soil ecosystem and is greatly affected by environmental factors, such as temperature. The objective of this study is to illuminate relationship of organic C mineralization in aggregates with that in bulk soil,to evaluate sensitivity of organic C mineralization in soil aggregates to temperature relative to particle size and eventually to help understand mechanisms of the organic C mineralization in soil aggregates and its sensitivity to temperature.【Method】The soil used in this study was collected from a paddy filed of red soil fertilized with inorganic and organic manure for 20 years in Yujiang Country, Jiangxi Province, China.Five fractions of aggregates, i.e., >2 mm, 1～2 mm, 0.25～1 mm, 0.053～0.25 mm and <0.053 mm, were isolated with the wet-sieving technique. All the aggregates and bulk soil samples were moistened or dried till they reached 60% in water holding capacity and incubated at 15 ℃, 25 ℃ and 35 ℃, separately, for 35 d. Emissions of carbon dioxide(CO2) were monitored and measured during this period.【Result】Macroaggregates of >0.25 mm contained more organic C and total nitrogen(N) than microaggregates of <0.25 mm. C/N ratio in soil aggregates decreased with declining particle size. Mineralization rates of organic C in both bulk soil and soil aggregates decreased rapidly during the first 7 days of incubation, then gradually leveled off till a stable state in the end. In the soils incubated at 25 ℃ and 35 ℃, the fraction of soil aggregates >1 mm was the highest while the fraction of soil aggregates 0.053～0.25 mm was the lowest in cumulative organic C mineralization.What’s more, cumulative organic C mineralization in soil aggregates was significantly or ultra-significantly and positively related to the content of organic C and total N. The fractions, >2 mm and 0.25～1 mm, contributed the most to cumulative bulk soil organic C mineralization, reaching up to 34.6% and 28.8%, respectively, in contribution rate. With rising temperature, mineralization rate, cumulative mineralization and cumulative mineralization rate of organic C in bulk soil and aggregates all increased. Sensitivity of organic C mineralization(Q10) in soil aggregates to temperature varied in the range of 1.38～2.00, and was ultrasignificantly and positively related to organic C and total N contents as well as C/N ratio.【Conclusion】Macroaggregates of >0.25 mm play a key role in organic C mineralization in bulk soil. Temperature rise promotes organic C mineralization in soil aggregates. Sensitivity of organic C mineralization to temperature in soil aggregates is closely related to quantity and quality of organic matter in the aggregates.更多还原