Litter Decomposition And Carbon,Nitrogen And Phosphorus Release In Mature Pinus Sylvestris Var. Mongolica Plantations In Horqin Sandy Land

The litter of Pinus sylvestris var.mongolica plantation is an integral part of the material cycle and energy transformation in the sandy ecosystem,but the decomposition mechanism of Pinus sylvestris var.mongolica litter is still unclear.Based on this,this paper took the litter from mature forest land of Pinus sylvestris var.mongolica as the research object,and studied the variation characteristics of C,N,P,lignin,and cellulose content in the litter of Pinus sylvestris var.mongolica during the decomposition process under the conditions of different stand ages and stand densities.It’s a release rule.Multivariate regression analysis on the dominant factors of litter decomposition rate under different stand ages and stand densities,and explore the characteristics of nutrient element content changes in the process of litter decomposition under the interaction of stand age and stand density.The main findings are as follows:（1）P,lignin,and cellulose in the leaf litter of the three stand ages（43a,49a,and 56a）showed a continuous increase with the season;C showed a continuous decrease;N and N/P both showed an increase followed by a decrease;C/N and lignin/N showed a decrease followed by an increase.At the early stage of decomposition,C was significantly affected by stand age,and the decomposition rate of litter accelerated with the rise of temperature.As the main influencing factor controlling the decomposition of litter,N showed a significant upward trend.In the later period（November to May of the following year）,the climate was cold and dry,the soil biological activity decreased,the decomposition rate decreased,and the N/P decreased.In addition,the nutrient utilization efficiency of Pinus sylvestris var.mongolica plantation was higher with N content in the range of 2.73～31.89g·kg^-1and P content in the range of 2.73～31.89g·kg^-1,and the nutrient utilization efficiency of Pinus sylvestris var.mongolica is high,and the plantation of Pinus sylvestris var.mongolica has strong adaptability under extreme conditions.（2）P,lignin,and cellulose in leaf litter at three stand densities（400,625,and 800 N/hm²）show a continuous upward trend with seasonal changes;C shows a continuous downward trend;N and N/P show an upward and then a downward trend;C/N and lignin/N show a downward and then an upward trend.Stand density affects soil microbial activity and thus C concentration and lignin/N.In this study,N/P<25,the decomposition rate of leaf litter in Pinus sylvestris var.mongolica plantations was mainly limited by N content.（3）When the stand ages were 43a and 49a,the meteorological dominant factor of litter decomposition rate was light,and at 56a,temperature.When the stand density was 400 N/hm²,the meteorological dominant factor of litter decomposition rate was the humidity,and when the stand density was 625 and 800 N/hm²,it was light;When the stand age was 43a,the substrate quality dominant factor of litter decomposition rate was the initial C/P,and when the stand age was 49a and 56a,it was the initial lignin/N.When the stand density was 400 N/hm²,the substrate quality dominant factor of litter decomposition rate was initial N content,625 N/hm²was initial cellulose content,and 800 N/hm²was initial lignin/N.The interaction between stand age and stand density had significant effects on the nutrient content and stoichiometry of litters in different seasons（p<0.01）.There are 20 Figures,5 tables and 141 references in this paper.