不同来源可溶性有机物对亚热带森林土壤CO2排放的影响

Effects of different sources of dissolved organic matter on soil CO_2 emission in subtropical forests

采用室内培养法,比较分析了亚热带地区杉木(Cunninghamia lanceolata)和米槠(Castanopsis carlesii)鲜叶及凋落叶浸提得到的可溶性有机物(dissolved organic matter,DOM)组成和化学性质差异对土壤CO2排放的影响。结果表明:添加不同来源的DOM后,土壤CO2瞬时排放速率在培养第1天内均显著高于对照(添加去离子水)(p<0.05),分别比对照增加了91.5%(添加杉木鲜叶DOM)、12.8%(添加米槠鲜叶DOM)、61.0%(添加杉木凋落叶DOM)和113.3%(添加米槠凋落叶DOM),但培养5天后,分别下降到对照的24.1%、8.3%、14.6%和13.2%,随后逐渐趋于平稳。单次添加外源DOM到土壤中,引起土壤CO2排放速率增加的强度较大,但持续时间短暂。培养31天时,添加不同来源的DOM均对土壤CO2累积排放量具有显著影响(p<0.05),而在培养59天时,添加杉木鲜叶和凋落叶DOM的土壤CO2累积排放量均显著高于添加米槠鲜叶和凋落叶DOM的土壤CO2累积排放量,但添加相同树种鲜叶与凋落叶DOM的土壤CO2累积排放量之间差异不显著。培养结束后,添加杉木鲜叶DOM和杉木凋落叶DOM后增加的土壤碳排放量,分别是外源添加可溶性有机碳量的1.76倍和2.56倍,而添加米槠鲜叶DOM和米槠凋落叶DOM后增加的土壤碳排放量只占外源添加可溶性有机碳量的22.5%和50.0%,表明单次添加不同来源的DOM对土壤总有机碳库的影响是不一致的。

Aims Dissolved organic matter （DOM） is an important carbon and nutrient pool, but the effects of different sources of DOM on soil carbon cycling are less well understood. Our objective in this study was to investigate how differences in the quantity and quality of DOM from fresh leaves and leaf litter of Cunninghamia lanceolata and Castanopsis carlesii affected soil CO2 fluxes in a laboratory incubation experiment. Methods Mineral soils （0-10 cm） from an ll-year-old Cunninghamia lanceolata plantation in Sanming of Fu- jian Province, China, were incubated for 59 days after adding the DOM from fresh leaves and leaf litter of Cun- ninghamia lanceolata and Castanopsis carlesii. Carbon （C） mineralization during incubation was determined us- ing CO2 respiration method. Important findings Compared to the controls, the rates of C mineralization significantly increased by 91.5%, 12.8%, 61.0% and 113.3% on day 1, following additions of DOM from fresh leaves and leaf litter of Cunningha- mia lanceolata and Castanopsis carlesii, respectively; the magnitudes of the increases declined to 24.1%, 8.3%, 14.6% and 13.2% by day 5, indicating that addition of DOM had significant but short-term influences on soil CO2 emission. DOM from different sources had significant effects on the cumulative CO2 production following addi- tion of DOM by day 31 （p 〈 0.05）. After 59 days of incubation, the cumulative quantity of mineralized C follow- ing addition of DOM from fresh leaves and leaf litter of Cunninghamia lanceolata was significantly greater than that from those of Castanopsis carlesiL while there was no significant difference in the cumulative CO2 produc- tion between DOM from fresh leaves and leaf litter of the same tree species, suggesting that difference in tree species had a greater influence on C mineralization than difference in the degree of leaf decay. Addition of DOM originated from fresh leaves and leaf litter of Castanopsis carlesii resulted in increased C mineralization by 22.5% and 50.0% of C added over the course of 59 day incubation, whereas increases by additions of DOM from fresh leaves and leaf litter of Cunninghamia lanceolata were 1.76 times and 2.56 times, respectively. Thus, a single ad- dition of different sources of DOM may lead to diverse effects on total soil carbon stocks.