Temperature And Nitrogen Deposition Driven Litter Decomposition Mechanisms

In recent years,due to the rapid development of industry and agriculture,the impact of global warming and atmospheric nitrogen deposition on human health and ecosystem balance has received increasing attention.Litter is an indispensable part of the ecosystem.It plays an important role in the nutrient cycling,energy flow,biodiversity,and productivity functions of the ecosystem.Therefore,the effects of elevated temperature and nitrogen deposition on nutrient return during litter decomposition It has also become one of the hot areas that many scholars have studied.Based on this,a spatial shift was simulated in the experiment to simulate temperature increase?2.5°C?and NH₄NO₃ as an external nitrogen source(CK:0 gNm^-2a^-1,LN:2.5gNm^-2a^-1,MN:5gNm^-2a^-1,HN:7.5gNm^-2a^-1)Nylon mesh bag method was adopted from October 2014 to October 2016.During the two years,the needle leaves of litters were investigated under temperature increase and different concentrations of nitrogen deposition.Loss of dry mass,and release rates of organics and elements.The response of temperature and nitrogen deposition to the increase of temperature and nitrogen deposition in the Greater Khingan Mountains was studied.The mechanism of temperature and nitrogen deposition on litterfall nutrient return in the Greater Khingan Mountains was studied.It was the temperate temperate forest ecosystem in Greater Khingan region and even northern China.Nutrient cycle provides an important reference.1.Under natural conditions,Larix gmelinii?Rupr.?Kuzen litter mainly relies on the decomposition of freezing and thawing in non-growth season.Nitrogen deposition significantly increases the loss rate of leaf litter.The increase in temperature significantly accelerates the rate of mass loss of Larix gmelinii?Rupr.?Kuzen during the growing season?6.8%?.Under the driving of temperature and nitrogen,the mass loss of litter of litter in Larix gmelinii?Rupr.?Kuzen was significantly increased,and its mass loss rate increased by 18.2%under the temperature increase of 2.5°C and MN treatment.The increase of temperature accelerated the release rate of crude fat,polyphenols,cellulose,lignin,and C,K,Mg,Mn,and Zn in leaf litter to increase the decomposition rate of litter.Nitrogen deposition accelerates the release rate of crude fat,polyphenols,cellulose,lignin,and C,P,K,Ca,Mg,Mn,and Zn in leaf litter to increase the decomposition rate of litter.2.The four organic compounds in Larix gmelinii?Rupr.?Kuzen were directly released.Polyphenols and crude fat were mainly released in the first non-growth season.Cellulose was released mainly in the first year,and lignin was released mainly in the second non-growth season.Nitrogen deposition and temperature both significantly promote organic release.C,K are direct release modes,N,Mn,Fe,Zn are enriched release modes,P,Ca,and Mg are leaching-enrichment-release modes.Nitrogen deposition did not change the element release pattern,but the temperature changed the release pattern of Ca and Mg.Temperature and nitrogen deposition drive the change of N,Ca,Mg,and Zn release modes.3.In the experiment,C,Ca,Mn,and Zn are true nitrogen-promoting elements,and their absolute content and relative content have a tendency of nitrogen deposition to promote release.Among them,Ca,Mn,and Zn show higher nitrogen concentration,which promotes the trend obvious.The N,P,K,and Fe elements are nitrogen suppressing elements.4.During the litter decomposition process,nitrogen deposition changes the correlation between the mass loss of litter and organic matter and elements.Each nitrogen treatment reduced the correlation between nitrogen and four organic compounds in leaf litter.Ca and Fe were the elements with the largest and smallest masses measured in leaf litter,and Ca and Fe were the mass and concentration of nitrogen after each concentration.The most relevant element of loss.5.The size of element release in natural decomposition is K>P>C>Mg>N>Ca>Fe>Zn>Mn.The release amount under low nitrogen conditions is P>K>C>Mg>N>Ca>Mn>Zn>Fe,under the middle nitrogen conditions the release amount is K>P>C>Mg>Ca>N>Zn>Mn>Fe.Under high nitrogen conditions,the release amount is K>P>C>Mg>Ca>N>Zn>Mn>Fe,the release of K>Mn>C>P>Mg>Ca>N>Zn>Fe after the temperature rises,the temperature rises and the release amount under nitrogen deposition is K>C>P>Mn>Mg>N>Ca>Zn>Fe.