| Soil CH4 uptake is the result of the combined action of CH4 production,transmission and oxidation.Forest soil is the most effective biological sink of atmospheric CH4,accounting for 52%of the global soil CH4 uptake.Nitrogen?N?input is one of the key factors affecting the CH4 uptake process in forest soils.At present,China has become the third largest N deposition area after Europe and North America,with 12.9-21.1 kg ha–1 yr-1.Compared with the forests with insufficient N deposition,the CH4 uptake in the subtropical bamboo forest soil with high N deposition would be more sensitive to N deposition.In this study,the intensive management of Moso bamboo plantations in subtropical regions was studied.The effect of different doses and different types of N input?CK,L-NH4Cl,H-NH4Cl,L-KNO3,H-KNO3?on soil CH4 uptake,temperature,water content,pH,NH4+-N and NO3--N content,water soluble carbon and nitrogen content?WSOC,WSON?,microbial biomass carbon and nitrogen content?MBC,MBN?and enzyme activity in Moso bamboo forests were measured The relationship between soil CH4 uptake and soil environmental factors was explored,the effects of different doses and different types of nitrogen input on soil CH4 uptake and its mechanism were revealed.It provides a reference for the change of atmospheric CH4 uptake caused by nitrogen deposition and its impact on forest ecosystems.The main findings obtained were as follows:?1?Under different doses and different types of nitrogen input,the soil CH4 uptake in Moso bamboo plantation shows a significant seasonal change.Compared with the control,the application of low doses of NH4Cl and KNO3 resulted in a decrease in the annual cumulative soil CH4 uptake in the Moso bamboo plantation by 82.36%and 82.14%,respectively.The high doses of NH4Cl and KNO3resulted in a decrease in the Annual cumulative soil CH4 uptake in the Moso bamboo plantation by87.33%and 88.94%,respectively.In general,the inhibitory effect of nitrogen addition on soil CH4uptake increased with the increase of nitrogen level,there was no significant difference between different types of nitrogen addition.?2?Different doses and different types of nitrogen input had no significant effect on 5 cm soil temperature and soil moisture,but significantly increased soil NH4+-N content,WSON content,MBC content,MBN content,and increased with increasing nitrogen levels.In addition,nitrogen deposition significantly reduced soil pH.?3?The activity of soil enzymes?urease,invertase and catalase?showed a certain variation with temperature,generally reaching the lowest value in the winter and peak in the summer.Under different doses and different types of N input,nitrogen treatment increased the soil urease activity and catalase activity by 7.84-23.64%and 4.58–47.06%,respectively,except for H-KNO3 treatment,there was no significant difference in soil urease activity and catalase activity between the other treatments.Nitrogen treatment significantly reduced the soil invertase activity,which decreased by 8.23-19.21%.?4?There was a significant negative correlation between soil CH4 uptake and soil moisture,WSON,soil NH4+-N content,soil NO3--N content and invertase activity,but no significant correlation with soil temperature?5cm?,soil pH,WSOC,MBC,MBN and urease activity.Multivariate regression analysis all significant continuous variables and categoricalvariables explained more than 54.06%of the variation in soil CH4 uptake fluxes.Different doses and different types of nitrogen input had different effects on soil CH4 uptake and soil environmental factors?such as temperature,moisture,NH4+-N content,soil NO3--N,enzyme activity,etc.?.The results showed that the nitrogen input significantly inhibited the soil nitrogen content and enzyme activity,which significantly inhibited the soil CH4 uptake in the bamboo forest. |
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