可溶性有机质输入对杉木人工林表层土壤有机碳矿化的激发效应

摘要

Dissolved organic matter (DOM) is one of the main carbon and nutrient pools in the forest ecosystem.Its effect on carbon sequestration in forest soil has received great attention.However,the influence of DOM on the organic carbon mineralization in forest soil is still unclear.Here,a short-term (36 h) incubation experiment was conducted to measure δ13 C within soil CO2 efflux following soil priming effects caused by the addition of DOM from leaf and root litter of Castanopsis carlesii and Cunninghamia lanceolata.The results showed that CO2 efflux from Castanopsis carlesii leaf litter DOM and Cunninghamia laneeolata leaf litter DOM peaked at 12 h,being 8.0 and 3.4 times higher than that at 2 h,and 4.6 and 7.0 times higher than that at 36 h,respectively.The CO2 efflux from soil organic carbon (SOC) was also highest at 12 h and was 10.1 and 6.3 times higher than that in the control.The use of 13C-labeled DOM additions allowed the total respired CO2 to be distinguished into that derived from the added DOM and that from SOC mineralization.The cumulative CO2 emission from added litter DOM was significantly greater than that from the added root litter DOM.In addition,the cumulative emission of CO2 from Castanopsis carlesii leaf litter DOM was significantly greater than that from Cunninghamia lanceolata leaf litter DOM.There was a significant positive relationship between soil CO2 efflux and the content of dissolved organic carbon.DOM from different sources had different priming effects (PEs) on SOC mineralization.During the 36 h of incubation,soils amended with leaf litter DOM always had a higher PE than those amended with root litter DOM.At 5 h,for all soils amended with DOM,the PE reached the peak.At 36 h,soil amended with Cunninghamia lanceolata root litter DOM changed from positive to negative PE.The microbial mechanisms of the priming effects of DOM inputs on SOC mineralization will be studied in future.%可溶性有机质(dissolved organic matter,DOM)是生态系统主要的可移动碳库及重要的养分库,它对森林土壤碳吸存的影响已引起高度关注,但DOM对森林土壤有机碳矿化的影响及机制仍不清楚.通过室内为期36 h的短期培养实验,利用13C稳定同位素示踪技术,探究杉木(Cunninghamia lanceolata)凋落叶DOM、米槠(Castanopsis carlesii)凋落叶DOM、杉木死根DOM、米槠死根DOM输入对11年生杉木人工林表层(0-10 cm)土壤有机碳矿化的激发效应,以期揭示DOM在森林碳循环中的作用,对于完善森林碳循环模型有重要意义.研究结果表明:通过13C标记区分不同来源CO2后发现添加米槠凋落叶DOM和杉木凋落叶DOM处理中来自DOM的CO2排放速率前期迅速升高,至12h达到最大值,分别为第2小时的8.0和3.4倍,之后下降,第12小时分别为第36小时的4.6和7.0倍;来自土壤有机碳的CO2排放速率同样在第12小时达到最大值,分别为同时间点对照的10.1倍和6.3倍.对不同来源CO2累积排放量进行区分发现,土壤添加凋落叶DOM后来自DOM的CO2累积排放量显著大于添加死根DOM的(P＜0.01),其中来自米槠凋落叶DOM的CO2累积排放量显著大于来自杉木凋落叶DOM的(P＜0.05),这与添加不同来源DOM中DOC含量呈显著正相关(P＜0.001).不同DOM添加对土壤有机碳矿化的激发效应强度不同,培养36h期间添加凋落叶DOM后土壤有机碳激发效应强度始终高于添加死根DOM的.添加米槠凋落叶DOM、杉木凋落叶DOM、米槠死根DOM、杉木死根DOM所引起的激发效应都在第5小时达到峰值,第36小时时添加杉木死根DOM出现负激发效应.可见,添加不同来源DOM对土壤原有有机碳矿化产生了不同的激发效应,这除了与不同来源DOM性质有关外,还可能与DOM添加后土壤微生物群落组成变化有关.有关DOM添加对土壤有机碳矿化影响的微生物学机制有待进一步研究.