典型设施环境条件对土壤活性有机碳及腐殖物质碳的影响

摘要

为明确设施环境对土壤有机碳形态变化的影响,选取武汉城郊设施土壤为研究对象,分别设置环境温度(4、10和25℃)、土壤酸化(土壤pH分别为6.89、6.11和5.30)和土壤盐渍化〔土壤w(可溶性盐分)分别为1.90、3.05和5.01 g∕kg〕3种典型设施环境条件,通过为期90 d的室内模拟强化试验,研究以上3种典型设施环境条件对土壤活性有机碳动态变化、腐殖物质碳组成及有机碳矿化率的影响.结果表明:与4℃的对照处理相比,随着设施环境温度升高,土壤w(MBC)(MBC为微生物生物量碳)和w(ROOC)(ROOC为易氧化有机碳)呈上升趋势,25℃时的最大增幅分别达19.43%和55.56%;而土壤w(DOC)(DOC为可溶性有机碳)总体呈先升后降的趋势,10℃下最大增幅为17.23%,25℃下最大减幅为60.89%.与对照土壤〔pH为6.89,w(可溶性盐分)为1.90 g∕kg〕相比,土壤pH为5.30的酸化处理下w(MBC)和w(ROOC)平均降幅分别为29.80%和5.93%,土壤w(可溶性盐分)为5.01 g∕kg的盐化处理下的平均降幅分别为35.64%和6.26%,而酸化和盐化使土壤w(DOC)较对照的平均增幅分别达58.19%和119.73%.此外,设施环境温度提高会降低土壤有机碳矿化率和HU(胡敏素碳)所占比例,其HA∕FA(胡敏酸碳富里酸碳含量之比)较对照增加了1.05倍;而土壤酸化和盐化会使有机碳矿化率较对照分别增加3.78和7.80倍,其HA∕FA较对照分别降低了65.72%和73.21%.可见,提升设施环境温度、减缓或改善设施土壤的酸化及盐化问题,均有利于设施土壤的固碳减排.%Both labile organic carbon and humus substance carbon are main carbon pools in soil, and they play essential roles in soil carbon cycling. The effects of three typical greenhouse parameters including environmental temperature ( 4, 10 and 25 ℃) ;soil acidification ( pH 6. 89, 6. 11 and 5. 30 ) and salinization ( 1. 90, 3. 05 and 5. 01 g∕kg for soluble salt ) on organic carbon in the greenhouse soil were investigated through laboratory experiments. The dynamics of microbial biomass carbon (MBC), dissolved organic carbon ( DOC) and readily oxidizing organic carbon ( ROOC) in greenhouse soil were determined during 90 days'incubation period. The soil humus substance carbon at the 90th day and the mineralization rate of organic carbon at the 12th day were also analyzed. The results showed that, compared with the control ( at 4 ℃) ;the contents of MBC and ROOC in greenhouse soil increased significantly with the rising of environmental temperature, with maximum increases of 19. 43% and 55. 56% at 25 ℃, respectively, whereas the contents of DOC increased by 17. 23% at 10 ℃ and decreased by 60. 89% at 25 ℃. Both acidification and salinization of greenhouse soil could reduce the contents of MBC and ROOC while increasing the content of DOC. Compared with the control ( at pH 6. 89 and 1. 90 g∕kg for soluble salt) ;the contents of MBC and ROOC in acidified soil ( pH 5. 30) decreased by 29. 80% and 5. 93% on average, while the ones in salinized soil ( 5. 01 g∕kg for soluble salt) decreased by 35. 64% and 6. 26% on average, respectively. In contrast, the contents of DOC increased by 58. 19% and 119. 73% on average in acidified soil ( pH 5. 30) and salinized soil ( 5. 01 g∕kg for soluble salt) ;respectively. Helpfully, the increase in environmental temperature reduced the mineralization rate of soil organic carbon and decreased the percentage of humus carbon ( HU) ;whereas the ratio of humic acid carbon∕fulvic acid carbon ( HA∕FA ) at 25 ℃ was 1. 05 times higher than the control. Compared with the control, the mineralization rate of organic carbon in acidified soil (pH 5. 30) and salinized soil (5. 01 g∕kg for soluble salt) increased by 3. 78 and 7. 80 times, respectively. However, the ratio of HA∕FA decreased by 65. 72% and 73. 21%, respectively. Therefore, increasing environmental temperature and preventing greenhouse soil from acidification and salinization would be efficient strategies to sequestrate carbon and thus reduce CO2 emissions from greenhouse soils.