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以亚热带红壤丘陵区典型水田和旱地土壤为研究对象,向土壤中添加14C标记稻草,培养30 d后,提取与原位土壤中结构相似的14C可溶性有机碳(DOC);将14C-DOC加入水田和旱地土壤中,并设置45%、60%、75%、90%和105%田间持水量(WHC)5个水分梯度,在标准状态下(25℃)培养100 d,监测14C-DOC在土壤中的矿化过程.结果表明:培养100 d后,两种土壤中28.7%~61.4%的标记DOC被矿化为CO2,且5个水分条件下,水田土壤DOC的矿化率均显著高于旱地,这主要是由于水田土壤DOC的结构组成比旱地土壤更简单.好气条件(56%~75%WHC)有利于两种土壤DOC的分解,淹水条件(105%WHC)则有利于DOC的积累.土壤处于好气条件(45%~90%WHC)时,DOC的生物可分解率及易分解态所占比例均随着含水量的增加而增加.100 d内,水田和旱地易分解态DOC分别占其累积矿化量的80.5%~91.1%和66.3%~72.4%,说明DOC的生物可分解率主要由其易分解态组分所占比例决定.
14C-labeled DOC was added to paddy soils in typical paddy fields and upland soils of subtropical red soil hilly areas. After 14 days of cultivation, 14C-soluble organic carbon (DOC) And dryland soils. Five water gradients of 45%, 60%, 75%, 90% and 105% of field WHC were set up and cultivated for 100 days under standard conditions (25 ℃) The results showed that 28.7% -61.4% of labeled DOC in two soils were mineralized to CO2 after 100 days of incubation, and the mineralized rates of DOC in paddy soils were all significantly higher than those under five moisture conditions The dry land was mainly due to the fact that the composition of DOC in paddy soil was simpler than that in dry land, and the good gas condition (56% -75% WHC) was beneficial to the decomposition of DOC in both soils. Under flooding conditions (105% WHC) Accumulating.When the soil is in good condition (45% ~ 90% WHC), the DOC biodegradability and the proportion of easy decomposition state both increase with the increase of water content.Within 100 days, paddy field and dryland easily decomposable DOC Accounting for 80.5% -91.1% and 66.3% -72.4% of the cumulative mineralization respectively, indicating that the biodegradability of DOC is mainly determined by the proportion of its easily decomposable components Example decision.