Effects Of Simulated Nitrogen Addition On Decomposition Characteristics Of Single And Mixed Litters In Temperate Desert

Litter decomposition is a key process of nutrient cycle in the ecosystem,which plays an important role in maintaining ecosystem production,promoting nutrient cycle and supplying plant nutrients.As an important aspect of climate change,atmospheric nitrogen has deeply affected the structure and function of the desert ecosystem,but the impact mechanism on the decomposition of desert plants is not clear.Here,this study is on the southern edge of Gurbantunggut Desert,using the single and mixed-species litter decomposition of Haloxylon ammodendron,Tamarix ramosissima,Karelinia caspia,Sophora alopecuroides and Salicornia europaea as the decomposition matrix.Four treatments:N₀(0 g N m^-2),N₅(5g N m^-2),N₁₀(10 g N m^-2)and N₂₀(20 g N m^-2).The influence of exogenous nitrogen addition on the decomposition rate and nutrient release is studied,which reveals the response mechanism of the desert litter decomposition to the atmospheric nitrogen settlement,and provides a key theoretical basis for the complete construction of the carbon and nitrogen cycle model of the desert ecosystem.The results are as follows:1)After decomposition of 345 days,the mass remaining percentage each species decreases with increasing decomposition time,including the highest of K.caspia(59.04%)and the lowest of S.europaea(43.55%).The nutrient dynamics of individual litter showed net release mode,and its decomposition rate was significantly positively associated with initial P content,cellulose and semilellulose content,and significantly negatively correlated with the initial lignin content.2)The non-additive effect of the mixed litter decomposition is different from the decomposition time.In the early stage of decomposition(0?29 d),only the combination of K.caspia-S.alopecuroides exhibited a synergistic non-additive effect.In the total experiment period(0?345 d),the mixture litter of T.ramosissima-S.europaea and the mixture litter H.ammodendron-K.caspia-S.alopecuroides exhibited an additive effect.The non-additive effect of mixed nutrient release of litter varies with species composition and decomposition time.In the early stage of decomposition(0?182 d),the C release of the K.caspia-S.alopecuroides exhibited a synergistic non-additive effect.In the late decomposition period(259?345 d),the release of P and K from the mixture litter of K.caspia-S.alopecuroides,and the release of P from the mixture litter of H.ammodendron-K.caspia-S.alopecuroides exhibited antagonistic non-additive effects.Throughout the experimental period(0?345 d),the N release of the mixture litter of H.ammodendron-K.caspia-S.alopecuroides exhibited an antagonistic non-additive effect.3)Only the N₁₀ treatment significantly inhibited the decomposition rate of H.ammodendron.In addition,the addition of N addition not affect the decomposition rate of T.ramosissima,K.caspia,S.alopecuroides,and Salicornia europaea.Besides,the N treatment significantly affected the N release of H.ammodendron,K.caspia,S.alopecuroides,S.europaea and the P release of S.europaea.4)In the litter mixture decomposition,only the N₂₀ treatment significantly promoted the decomposition of the mixture litter of K.caspia-S.alopecuroides.And the addition of N also affects the non-additive effect of litter mixing.Under N₁₀ treatment,the mixture litter of T.ramosissima-S.europaea exhibited an antagonistic non-additive effect.Under N₅ treatment,the mixture litter of H.ammodendron-K.caspia-S.alopecuroides exhibited a synergistic non-additive effect.In addition,N addition also affects the nutrient release of litter mixing and the non-additive effect of nutrient release.The addition of Nitrogen addition the release of N and P in the mixture litter of K.caspia-S.alopecuroides and the mixture litter of H.ammodendron-K.caspia-S.alopecuroides;suppresses the release of P from the mixture litter of T.ramosissima-S.europaea.At the same time,under N₁₀ treatment,the P release of the mixture litter of H.ammodendron-K.caspia-S.alopecuroides exhibites an antagonistic non-additive effect.In summary,the initial chemical composition of litter is an important factor affecting the decomposition of temperate deserts litter.The addition of exogenous nitrogen does not affect the decomposition rate of the litter,but affected the nutrient release of single and mixed litter,and affected the non-additive effect of mixed litter.It indicates that nitrogen deposition may affect the C balance of the ecosystem by changing the nutrient release of litter in the background of global change.