Study On Chemical Matrix Of Typical Grassland Litter Under Different Grazing Intensities

Litter is a bond about the conversion of the mater and energy between the ground and the underground.The decomposition and accumulation of the litter and the enrichment and release of its nutrients are of great significance to the material cycle of grassland ecosystem,and it is especially important for typical grasslands with relatively poor nutrients.This plot for long-term wild ecological positioning monitoring of typical grasslands is located in the east of Xilinhot.It examined the decomposition rule and chemical functional group change characteristics of four plant litters（Stipa grandis,Leymus chinensis,Anemarrhena asphodeloides and Cleistogenes squarrosa）and that of the four grazing gradients（control,light grazing,moderate grazing and heavy grazing）.There were the main results as followed:（1）The change law of decomposition rate of Stipa grandis,Leymus chinensis.And the late decomposition rate is lower than the decomposition rate in the initial stage for this four plant litters.（2）For Stipa grandis,Leymus chinensis and Cleistogenes squarrosa,the decomposition rate showed a significant positive correlation with the total P content,while a significant negative correlation with C/P and cellulose/P.Namely,the higher the P content of litter,the lower the C/P and cellulose/P,the faster the decomposition speed.（3）Under grazing,the decomposition rate of the four plants was much higher than that of the control.Stipa grandis and Leymus chinensis had the least residues under heavy grazing,and Anemarrhena asphodeloides and Cleistogenes squarrosa had the least residues under light grazing.Under grazing,the TP and lignin content was higher than the control,and the TC content was lower than the control.However,for TN content and cellulose content,grazing was not significant.With the increase of grazing intensity,litter decomposition changed from P limit to lignin limit.（4）The main functional groups of Stipa grandis,Leymus chinensis,Anemarrhena asphodeloides and Cleistogenes squarrosa are-OH;=C-H,-CH₂,-CH₃;C=O;C=O,=C-H.The functional group content of litter in different plants decreased rapidly in the early stage of decomposition,and the decreasing trend was slower in the later stage of decomposition.It is consistent with the trend of litter decomposition rate.At the end of the decomposition,the content of carbon-containing functional groups of Anemarrhena asphodeloides was the lowest,and Stipa grandis was the largest and the loss of common anemarrhena and Cleistogenes squarrosa was the largest,which is consistent with the characteristics of TC content of the litter during the decomposition.The lar and CH₃/CH₂ of Stipa grandis are the largest,the CH₃/CH₂ of Leymus chinensis is the smallest,and the lar of Anemarrhena asphodeloides is the smallest.The lar and CH₃/CH₂ of different plants decreased rapidly in the early stage,but decreased slowly in the later stage,which was consistent with the trend of decomposition rate change.The overall content of the main carbon-containing functional groups showed a decreasing trend and had the differences between the control and different grazing intensities conditions,which were consistent with the change trend of the total C content.During the decomposition of litter,CH₃/CH₂ and lar under grazing were lower than the control conditions,and the decrease was the largest under mild and moderate grazing,in other words,suitable grazing is beneficial to the decomposition of litter,which were consistent with the analysis results of the litter decomposition rate.The research results have a certain theoretical significance in explaining the litter decomposition process from the perspective of functional group changes,and it can also provide some practical guidance for grassland protection and grazing management.