Wang Ji-Fei, Tong Yao-Yao, Zhu Zhen-Ke, Chen Shan, Deng Yang-Wu, Ge Ti-da, Wu Jin-Shui
School of Resources and Environmental Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, China.
Key Laboratory of Subtropical Agriculture Ecology, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China.
Huan Jing Ke Xue. 2019 Feb 8;40(2):970-977. doi: 10.13227/j.hjkx.201806204.
The turnover of soil organic carbon (SOC) and the activity of soil microbes can be influenced by exogenous carbon. However, microbial response characteristics of the transformation and distribution of available organic carbon under different levels remain unclear in paddy soils. C-labeled glucose was used as a typical available exogenous carbon to simulate indoor culture experiments added at different levels of soil microbial biomass carbon (MBC) (0×MBC, 0.5×MBC, 1×MBC, 3×MBC, and 5×MBC) to reveal the process of C-transformation and distribution. The characteristics of microbial response in the process of exogenous carbon turnover was also monitored. The 96-well microplate fluorescence analysis was adopted to determine the activities of cellobiose hydrolase (CBH) and -glucosidase (-Glu). The results showed that, in 2 d of incubation, the ratio of labeled glucose carbon to dissolved organic carbon (C-DOC/DOC) or to SOC (C-SOC/SOC) was positively correlated with the amount of glucose added. The incorporation of glucose C (C) into MBC reached the highest value (18.96 mg·kg) at 3×MBC treatment but decreased thereafter. The C allocation rate was mainly positively correlated with MBC, Olsen-P, and DOC. At 60 d, C-DOC, C-MBC, and C-SOC decreased significantly to less than 0.02 mg·kg, 2 mg·kg, and 10 mg·kg in soil, and it was positively correlated with the amount of glucose added. Compared with CK, CBH enzyme activity increased significantly after the addition of glucose, and for the 3×MBC treatment it was increased by 22.6 times, which was significantly higher than those of other treatments (<0.05). However, -Glu enzyme activity increased only in the 3×MBC and 5×MBC treatments, wherein it decreased with increasing amounts of added glucose. NH-N, pH, -Glu, and CBH were the primary factors affecting the distribution rate of C. In conclusion, the conversion of exogenous carbon to SOC increased with increased amounts of added organic carbon. This changed the activity of soil enzymes; however, microbial utilization of exogenous carbon may have a saturation threshold. Within the saturation threshold, the conversion rate of organic matter was directly proportional to the amount of added organic matter. When the saturation threshold was exceeded, the conversion rate of organic matter decreased. Therefore, the appropriate addition of exogenous carbon is beneficial, as it can increase SOC in rice fields and improve the quality of the crop growth environment.
土壤有机碳（SOC）的周转以及土壤微生物的活性会受到外源碳的影响。然而，不同水平下稻田土壤中有效有机碳转化与分布的微生物响应特征仍不明确。以¹³C标记的葡萄糖作为典型的有效外源碳，模拟室内培养实验，设置不同水平的土壤微生物生物量碳（MBC）（0×MBC、0.5×MBC、1×MBC、3×MBC和5×MBC），以揭示碳转化与分布过程。同时监测外源碳周转过程中微生物的响应特征。采用96孔微孔板荧光分析法测定纤维二糖水解酶（CBH）和β-葡萄糖苷酶（β-Glu）的活性。结果表明，在培养2天时，标记葡萄糖碳与溶解有机碳（C-DOC/DOC）或与SOC（C-SOC/SOC）的比值与添加的葡萄糖量呈正相关。葡萄糖碳（¹³C）掺入MBC在3×MBC处理时达到最高值（18.96 mg·kg⁻¹），此后下降。¹³C分配率主要与MBC、 Olsen-P和DOC呈正相关。在60天时，土壤中C-DOC、C-MBC和C-SOC显著下降至低于0.02 mg·kg⁻¹、2 mg·kg⁻¹和10 mg·kg⁻¹，且与添加的葡萄糖量呈正相关。与对照相比，添加葡萄糖后CBH酶活性显著增加，3×MBC处理时增加了22.6倍，显著高于其他处理（P<0.05）。然而，β-Glu酶活性仅在3×MBC和5×MBC处理中增加，且随添加葡萄糖量的增加而降低。NH₄⁺-N、pH、β-Glu和CBH是影响¹³C分配率的主要因素。综上所述，外源碳向SOC的转化随添加有机碳量的增加而增加。这改变了土壤酶的活性；然而，微生物对外源碳的利用可能存在饱和阈值。在饱和阈值内，有机质的转化率与添加有机质的量成正比。当超过饱和阈值时，有机质的转化率下降。因此，适当添加外源碳是有益的，因为它可以增加稻田中的SOC，改善作物生长环境质量。
