Analysis Of The Changes Of Litter Decomposition Characteristics Of Primitive Korean Pine Forests After Clear Cutting,northern China

In this study,the primitive Korean pine forest and the secondary broad-leaved forest after the clear cutting were used as the object,the decomposition rate and nutrient dynamics of the litter and the 0-5 cm soil nutrients and microorganisms in the lower part of litter.The change law of community structure was studied to explore the reasons for the formation of the difference,and the decomposition mechanism of litter was analyzed by structural equation model(SEM).The main conclusions are as follows:(1)1)Initial chemical components of litter in two forest types were significantly different(p<0.05).Except total nitrogen,total phosphorus,total potassium and total magnesium,the other indicators in original Korean pine forest were significantly higher than those in secondary broad-leaved forest(p<0.05);the decomposition rate of litter in original Korean pine forest was significantly higher than that in secondary broad-leaved forest(p<0.05);total carbon and total potassium in litter were released directly,and other elements were different.After 365 days of decomposition,except total phosphorus and potassium,other elements including total carbon in litter of the original Korean pine forest were significantly lower than those of the secondary broad-leaved forest(p<0.05),indicating that the original Korean pine released more nutrients into the soil through litter decomposition,and the material circulation rate was higher;the annual decomposition rate of litter was significantly positively correlated with the initial chemical components of total nitrogen and calcium,(p<0.05),there was a significant negative correlation with total carbon,lignin,carbon/nitrogen and lignin/nitrogen(p<0.05).(2)After litter decomposition for 0 days,the soil total nitrogen content of the original Korean pine forest was significantly higher than that of the secondary broad-leaved forest(p<0.05),whereas the organic carbon,available phosphorus and available potassium were on the contrary.After 365 days of litter decomposition,the total nitrogen of the two forest types increased significantly(p<0.05),and the changes of available phosphorus and available potassium were inconsistent.The variation of organic carbon,available phosphorus and available potassium was not consistent;soil physical and chemical properties(temperature and water content)and litter bottom quality(total nitrogen,total phosphorus,total potassium,total calcium,total magnesium,lignin)were the main reasons for the change of soil nutrients.(3)The maximum contents of total fatty acids and their components in soil microorganisms of primary Korean pine forest and secondary broad-leaved forest were 275 days;NMDS analysis showed that the soil microbial communities of primary Korean pine forest were distinctly differentiated after litter decomposition for 0 days and 365 days;the response of fungi to decomposition changes was the lowest;the interaction of forest type and decomposition time on fungi,G-,actinomycetes was the lowest.AMF,protozoa and total PLFA biomass had significant effects(p<0.05).Soil temperature,pH and bulk density were the main factors to explain the changes of PLFA biomass in various soil groups.(4)VPA analysis showed that litter substrate quality had the greatest impact on litter decomposition,followed by soil microbial community and soil environmental factors.Based on SEM analysis,forest types indirectly affect litter decomposition through indirect changes in litter substrate quality,soil microbial characteristics and soil environmental factors.Among them,litter substrate(carbon/nitrogen and lignin)not only has a direct negative impact on litter decomposition,but also indirectly affects the decomposition of litter by microbial community,which is an important factor affecting litter decomposition.The change of biomass of bacteria and fungi is more important than that of other functional groups for the change of litter decomposition process.Seeds(water content and total nitrogen)are also particularly important for litter decomposition,which not only has the most direct impact on litter,but also indirectly afifects microbial community and litter substrate.