High nitrate leaching has been observed from the O horizons of some tropical forests;however,the drivers of high nitrate production(active nitrification)in these O horizons have not yet been identified.This study inve...High nitrate leaching has been observed from the O horizons of some tropical forests;however,the drivers of high nitrate production(active nitrification)in these O horizons have not yet been identified.This study investigated the drivers of active nitrification in the O horizon of tropical forest soils by focusing on two of the most widely recognized controlling factors of nitrification,total N,and pH.We collected mineral and O horizons from eight tropical forests in Cameroon,Indonesia,and Malaysia and measured gross nitrification rates.Some O horizons showed significantly higher gross nitrification rates than mineral horizons,indicating that these O horizons have a high potential for nitrification.Gross nitrification rates in the O horizons were positively correlated with both total N and pH,and the chemical properties(e.g.,total content of N,P,and base cations)were intercorrelated.These correlations suggested that the underlying driver of nitrification in the O horizon was nutrient richness in the litter.Results also indicated a threshold of gross nitrification rates around pH values of 5.5–6.0.We elucidate that active nitrification and subsequent high nitrate leaching from the O horizon could be driven by nutrient-rich litter,possibly derived from soil fertility and tree species.展开更多
Rapid litter turnover in tropical forests and during summer seasons might be due to increases in ligninolytic enzyme activities during warmer periods.We compared ligninolytic enzyme activity[lignin peroxidase(LiP),man...Rapid litter turnover in tropical forests and during summer seasons might be due to increases in ligninolytic enzyme activities during warmer periods.We compared ligninolytic enzyme activity[lignin peroxidase(LiP),manganese peroxidase(MnP),and laccase(Lac)]in the organic layers of forest soils across a global climate gradient.As expected,MnP activities in fresh litter layers increased with increasing air temperature.Litter Mn/lignin ratios correlate positively with MnP activity and more rapid litter turnover in warmer climates.In contrast,LiP and Lac activities are regulated by site-specific conditions.Lac activity is commonly observed in less acidic fresh litter layers,while LiP activity localizes in acidified and lignin-rich deeper organic layers.The widespread occurrence of MnP and an increase in MnP activities in warmer climates support efficient lignin degradation in the tropics and during summer seasons.High Mn/lignin ratios in fresh litter could be an indicator of lignin degradability by MnPproducing fungi across global climate gradients.展开更多
基金This study was supported by Center for Ecological Research,Kyoto University,a Joint Usage/Research Center,and financially supported by the Japan Society for the Promotion of Science(JSPS)KAKENHI(Grant numbers 24228007,17H06171,and 19J14572).The authors have no relevant financial or non-financial interests to disclose.
文摘High nitrate leaching has been observed from the O horizons of some tropical forests;however,the drivers of high nitrate production(active nitrification)in these O horizons have not yet been identified.This study investigated the drivers of active nitrification in the O horizon of tropical forest soils by focusing on two of the most widely recognized controlling factors of nitrification,total N,and pH.We collected mineral and O horizons from eight tropical forests in Cameroon,Indonesia,and Malaysia and measured gross nitrification rates.Some O horizons showed significantly higher gross nitrification rates than mineral horizons,indicating that these O horizons have a high potential for nitrification.Gross nitrification rates in the O horizons were positively correlated with both total N and pH,and the chemical properties(e.g.,total content of N,P,and base cations)were intercorrelated.These correlations suggested that the underlying driver of nitrification in the O horizon was nutrient richness in the litter.Results also indicated a threshold of gross nitrification rates around pH values of 5.5–6.0.We elucidate that active nitrification and subsequent high nitrate leaching from the O horizon could be driven by nutrient-rich litter,possibly derived from soil fertility and tree species.
文摘Rapid litter turnover in tropical forests and during summer seasons might be due to increases in ligninolytic enzyme activities during warmer periods.We compared ligninolytic enzyme activity[lignin peroxidase(LiP),manganese peroxidase(MnP),and laccase(Lac)]in the organic layers of forest soils across a global climate gradient.As expected,MnP activities in fresh litter layers increased with increasing air temperature.Litter Mn/lignin ratios correlate positively with MnP activity and more rapid litter turnover in warmer climates.In contrast,LiP and Lac activities are regulated by site-specific conditions.Lac activity is commonly observed in less acidic fresh litter layers,while LiP activity localizes in acidified and lignin-rich deeper organic layers.The widespread occurrence of MnP and an increase in MnP activities in warmer climates support efficient lignin degradation in the tropics and during summer seasons.High Mn/lignin ratios in fresh litter could be an indicator of lignin degradability by MnPproducing fungi across global climate gradients.
