Biochemical Characteristics Of Litter Decomposition Of Stipa Grandis And Cleistogenes Squarrosa

Grassland litter is the matter and energy source of decomposers and its decomposition process has attracted extensive attention.Litter decomposition in grassland not only affects the net productivity of grassland ecosystem by releasing mineral nutrients,but also is an important process of carbon turnover in grassland,which regulates the composition of soil organic matter.Therefore,a thorough understanding of litter decomposition process in grassland at the quality and molecular level is helpful to accurately assess and predict the size and turnover rate of plant organic matter pools in grassland soil.Stipa grandis steppe is the most typical grassland type in temperate grassland of China.In this paper,S.grandis and Cleistogenes squarrosa,the dominant plants in the typical steppe of S.grandis,were selected as the research objects,and the indoor decomposition experiments of leaf and root litter of single and two species were established.The mass loss of litter in the 0,30,50,70 and 120 days of litter decomposition was analyzed.The composition,decomposition characteristics and influencing factors of the biomacromolecules during litter decomposition were elucidated by using nuclear magnetic resonance(NMR)analysis and lipid extraction technology,and the relationship between the litter decomposition process at molecular and mass levels was revealed.The main results were as follows:(1)For the same plant species,the decomposition rate of leaf litter was significantly higher than that of root litter.The decomposition rate of litter was significantly affected by humidity.For the decomposition process of both mixed leaf and root litter,the mass loss and the release of total carbon and total nitrogen all showed an additive effect.The lower C/N was,the higher the decomposition rate of the litter was.(2)With the decomposition process proceeding,the content of cutin,suberin and O/N-alkyl carbon(carbohydrate),as well as aromaticity in leaf and root litters of both S.grandis and C.squarrosa decreased.The decomposition of binding lipids was not significantly affected by the length of the carbon chain and the type of functional groups.(3)The variation of the suberin monomer concentration in root litter of both S.grandis and C.squarrosa was significantly correlated with their mass loss exponentially,suggesting that suberin monomer was easy to decompose at the initial stage of decomposition but tended to be stable at the later decomposition stage,so the turnover of organic matter in roots might be underestimated when biomarkers and source materials were assumed to degrade similarly for the both plant species.