Effects Of Simulated Precipitation Change On N₂O Flux In Songnen Meadow Steppe

Research data by several scientists focused on global warming associated changes in precipitation pattern and its ecological consequences.The variation of precipitation amount as a form of precipitation pattern has received large attention.N₂O an important component of greenhouse gases can exist for a long-term in the atmosphere.This compound absorb the long-wave radiation in the atmosphere,which destroy the ozone layer,that have a significant impact on future global warming trends.Grassland soils are an important source of global N₂O production and are highly vulnerable to climate change,but the effect and its mechanism of N₂O flux response to the precipitation change on the soil of grassland remain unclear.In this study,we establish the experiment at Songnen meadow steppe in Northeast China and the experiment had six precipitation treatment controlled by precipitation shelters.Increase precipitation treatment by 50%,30%and 0%?control?and decrease precipitation treatment by 30%,50%and 70%of the total amount of precipitation in the growing season.The gas samples were collected by static darkbox,and we aimed at the effects of above and belowground biomass,soil physical and chemical properties and soil N₂O flux caused by changing precipitation.The conclusions as follows:i The aboveground biomass was significantly affected by precipitation change treatments.In 2017 and 2018,the treatment that has been increased by 50%precipitation had the highest aboveground biomass,while that which decreased by 70%precipitation was the lowest.In both years,our treatment had no significant effect on belowground biomass,but the belowground biomass in the increased precipitation treatment was higher than that of decreased precipitation treatment,however,this difference was not significant.Aboveground biomass varied by years,and belowground biomass in 2018 is higher than that in 2017.The reason for this phenomenon may be related with precipitation in the early growing season of 2017.There was extreme precipitation events that occured in the late growing season,which inhibited the accumulation of belowground biomass.In 2017,there was no significant difference in root-shoot ratio among precipitation treatments;but in 2018,precipitation treatments significantly affected the root-shoot ratio,and the root-shoot ratio in decreased precipitation treatments were significantly higher than that in increased precipitation treatments.ii Precipitation treatment had significantly affected soil water content?SWC?.Soil pH was increased with the decrease of precipitation.Increased precipitation has significantly increased soil ammonium nitrogen content?NH₄⁺-N?,and decreased precipitation increased soil nitrate nitrogen content?NO₃^--N?.The increase of precipitation was beneficial to the accumulation of soil available nitrogen,but there was no significant difference among precipitation treatments.Soil total nitrogen?TN?and carbon?TC?showed an increasing trend with the increase of precipitation.The net mineralization rate and net nitrification rate in the soil were low at Songnen meadow steppe,and the change in precipitation had no significant effect on them.Increasing precipitation significantly increased soil microbial biomass carbon?MBC?and biomass nitrogen?MBN?,which indicated that a well SWC condition was conducive to the soil microorganisms.In 2017 and 2018,SWC,soil pH,NH₄⁺-N,NO₃^--N,TC,TN,MBC,and MBN displayed substantial seasonal variation.iii Under the precipitation treatments,soil N₂O flux showed obvious seasonal dynamics,and the annual average flux had significant differences.In both years,the maximum flux appeared in July.The N₂O flux in the treatment increased by 30%precipitation was significantly higher than that increased by 50%and decreased by 70%precipitation treatments in 2017.Soil N₂O flux was increased with the increase of precipitation in 2018.Under different precipitation treatments in 2017 and 2018,SWC,NH₄⁺-N,NO₃^--N,MBC,MBN had a positive correlation with N₂O flux,while soil pH had a negative correlation with N₂O flux.The effects of precipitation change on soil physical-chemical properties and soil microbial activity indirectly affected soil N₂O flux.The results showed that the aboveground biomass was sensitive to changes in the precipitation amount at Songnen meadow steppe.The two-years experiment revealed that N₂O flux obviously showed seasonal dynamics and the annual average N₂O flux was significantly increased with the increase of precipitation.In the future,the variation of precipitation pattern may affect soil N₂O flux by changing soil physical and chemical properties and soil microbial activity at Songnen meadow steppe.Therefore,the results of this study have important theoretical significance for studying the mechanism of greenhouse gas emissions from grassland soil under the change of precipitation pattern.