凋落物输入变化对森林土壤CH_(4)吸收的影响

The effect of litter input changes on CH_(4) uptake in forest soils

甲烷(CH_(4))是仅次于二氧化碳的第二大温室气体。森林土壤作为大气CH_(4)“汇”,在全球CH_(4)预算中发挥着重要作用。凋落物是森林土壤重要的碳库和养分库,凋落物分解既增加了土壤碳和养分归还,也降低了土壤表面氧气浓度,可能影响土壤CH_(4)氧化和扩散。但目前对凋落物输入是否改变森林土壤CH_(4)吸收的认识仍不清晰。本研究在福建三明国家野外站通过凋落物输入微宇宙实验,连续监测了杉木人工林凋落物去除后土壤CH_(4)通量的变化,发现去除凋落物使杉木人工林土壤CH_(4)吸收量显著增加。在此基础上,利用Meta分析进一步整理了其他6个森林样点凋落物(叶和根)去除和加倍输入对土壤CH_(4)吸收的影响,发现凋落物去除使阔叶林土壤CH_(4)吸收显著增加16.5%。相反,凋落物加倍输入使阔叶林和针叶林土壤CH_(4)吸收分别显著降低了11.1%和20.0%,说明凋落物加倍输入降低了森林土壤CH_(4)“汇”的功能。这些结果表明,凋落物输入是影响森林土壤CH_(4)吸收的重要因素,凋落物层可能通过降低土壤表面氧气浓度,减少森林土壤对大气CH_(4)的吸收。

Methane(CH_(4))is the second important anthropogenic greenhouse gas after carbon dioxide(CO_(2)).For-est soils are a sink for atmospheric CH_(4) and play an important role in modulating global CH_(4) budget.Litter is impor-tant carbon and nutrient sources for forest soils.Litter decomposition could increase soil carbon and nutrient concen-trations and reduce oxygen concentration beneath the soil surface as well as the oxidation and diffusion of soil CH_(4).However,it remains unclear whether litter input changes CH_(4) uptake in forest soils.In this study,a microcosm experiment was conducted in a subtropical forest,and soil CH_(4) flux under the conditions with and without litter input was monitored monthly by chambers in a Chinese fir(Cunninghamia lanceolata)plantation over one year.We found that litter removal significantly increased soil CH_(4) uptake in Chinese fir plantation.We further analyzed the changes in soil CH_(4) flux after litter removal(leaf and root)and double litter input at six forest sites in other cli-matic zones.We found that litter removal significantly increased soil CH_(4) uptake in broadleaved forests by 16.5%.On the contrary,double litter input decreased soil CH_(4) uptake by 11.1%and 20.0%in broadleaved and coniferous forests,respectively,suggesting that the function of CH_(4) sink in forest soils decreased with additional litter input.Our results suggest that litter input is an important factor affecting CH_(4) flux uptake in forest soils,and that litter layers may reduce atmospheric CH_(4) uptake by forest soils through reducing the oxygen concentration beneath soil surface.