黄色石灰土不同粒径团聚体有机碳矿化对温度的响应

Temperature Response of Organic Carbon Mineralization of Aggregateswith Different Particle Sizes in Yellow Limestone

石灰岩(CaCO_3)发育是西南喀斯特地貌的主要成因,且石灰岩发育而成的石灰土对全球温室气体的排放产生了巨大的影响,但石灰土不同粒径团聚体中的有机碳在不同温度下的矿化特征尚不清楚。因此,本研究通过室内模拟培养试验结合湿筛法和碱液吸收法探究了15℃、25℃和35℃下黄色石灰土>0.25 mm、0.053~0.25 mm、0.002~0.053 mm和<0.002 mm粒径团聚体有机碳的矿化特征。结果表明:随团聚体粒径降低,土壤有机碳含量逐渐降低(P<0.05),其中,>0.25 mm有机碳含量为15.67 g/kg,<0.002 mm有机碳含量为0.59 g/kg;在培养的第1天,三种温度下各粒径团聚体有机碳矿化速率均达到峰值,随后快速下降并逐渐趋于稳定;且0.053 mm^0.25 mm团聚体有机碳的矿化速率(14.37~31.99 mg/(kg·d))和累积矿化量(100.67~223.92 g/kg)最大,是最低的<0.002 mm粒径团聚体的1.01~1.28倍;各粒径团聚体可矿化有机碳比例分别为:>0.25 mm(0.41%~0.91%)、0.053~0.25 mm(0.42%~0.93%)、0.002~0.053 mm(0.44%~0.79%)和<0.002 mm(0.41%~0.73%)(P<0.05)。其次,在低温(15℃)下升温,0.053~0.25 mm团聚体有机碳Q_(10)值(1.56)最大,而常温(25℃)下升温,则是>0.25 mm团聚体有机碳Q_(10)值最大(1.68);且0.053~0.25 mm团聚体有机碳的潜在可矿化量C_0(111.62~239.59 mg/kg)及矿化速率常数K(0.41~0.44)均大于其余各粒径团聚体。综上所述,黄色石灰土0.053~0.25 mm粒径团聚体有机碳矿化对升温的响应强烈,>0.25 mm和0.002~0.053 mm粒径团聚体次之,而<0.002 mm粒径团聚体有机碳矿化对升温响应最弱;固碳能力依次为:(<0.002 mm)>(0.002~0.053 mm)>(>0.25 mm)>(0.053~0.25 mm)。

The development of limestone(CaCO 3)is the main cause of karst landform in Southwest China,and the limestone soil has a great impact on the global greenhouse gas emissions,but the mineralization characteristics of organic carbon in different size aggregates of limestone soil at different temperatures are not clear.Therefore,this study used indoor simulated cultivation experiments combined with wet sieve method and lye absorption method to explore the mineralization characteristics of organic carbon in mm-sized aggregates,including limestone>0.25 mm,0.053 mm^0.25 mm,0.002 mm^0.053 mm and<0.002 at 15℃,25℃and 35℃.The results showed that as the aggregate size decreased,the soil organic carbon content gradually decreased(P<0.05),where>0.25 mm organic carbon content was 15.67 g/kg and<0.002 mm organic carbon content was 0.59 g/kg;on the first day of culture,the mineralization rate of organic carbon in aggregates with different particle sizes reached the peak under three temperatures,then rapidly decreased and gradually stabilized;the mineralization rate(14.37-31.99 mg/(kg·d))and cumulative mineralization amount(100.67-223.92 g/kg)of 0.053 mm^0.25 mm aggregates were the highest,which were 1.01~1.28 times of the lowest<0.002 mm aggregates;the proportions of mineralizable organic carbon of each particle size aggregate were:>0.25 mm(0.41%~0.91%),0.053 mm^0.25 mm(0.42%~0.93%),0.002 mm^0.053 mm(0.44%~0.79%)and<0.002 mm(0.41%~0.73%)(P<0.05).Secondly,when the temperature was raised at low temperature(15℃),the Q10 value(1.56)of the organic carbon of the aggregates from 0.053 mm to 0.25 mm was the largest,while at room temperature(25℃),the Q 10 value of the organic carbon of the aggregates of>0.25 mm was the largest(1.68);the potential mineralizable amount C 0(111.62~239.59 mg/kg)and the mineralization rate constant K(0.41~0.44)of the organic carbon in the aggregates of 0.053 mm to 0.25 mm were larger than those of the other aggregates.In summary,the mineralization of 0.053 mm^0.25 mm agglomerates organic carbon in yellow limestone responded strongly to temperature rise,followed by>0.25 mm and 0.002 mm^0.053 mm agglomerates,and<0.002 mm agglomerates organic carbon mineralization.The organic carbon mineralization of aggregates<0.002 mm has the weakest response to heating.The carbon-fixing capacity was:(<0.002 mm)>(0.002 mm^0.053 mm)>(>0.25 mm)>(0.053 mm^0.25 mm).