The Effect Of Litter Input On Soil Organic Carbon Accumulation And Stability In Typical Subtropical Forests

Soil carbon pool is the largest carbon pool in terrestrial ecosystem.Forest soil carbon pool is the most important part of soil carbon pool,which plays an important role in maintaining the global carbon cycle.However,the effect of litter input on forest soil carbon accumulation and stability remains unclear.The subtropical region of southern China is the main forest distribution area in China,with various forest types,and the main distribution area of artificial forest in China.Therefore,the effect of litter input on soil organic carbon accumulation and stability is of great value in understanding the forest soil carbon cycle.Three typical forest ecosystems(natural forest,Chinese fir plantation and Masson pine forest)were selected from Xiqin teaching forest farm of Fujian Agriculture and Forestry University,Nanping City,Fujian Province.The main contents of this study are as follows:(1)soil organic carbon storage and soil aggregate carbon pool composition characteristics of different forest ecosystems.(2)Effects of aboveground and underground litter inputs on soil organic carbon content and soil aggregates carbon pool structure in different types of forest ecosystems.(3)New litter-derived-carbon accumulation and its distribution characteristics of different active organic carbon pools in soil after litter input above ground and underground.The main results of this study are as follows:(1)there was no significant difference in soil total organic carbon(TOC)and total nitrogen(TN)content in topsoil 0-20cm among three typical subtropics forests t,but C:N in natural forest soil was significantly higher than that in Chinese fir plantation and Masson pine forest.Percentage content of>5mm and 2-5mm aggregates were mainly influences by forest type,Percentage content of>5mm aggregate of Nature forest was significantly higher than Chinese fir plantation and Masson pine forest,there was no significant difference of forest type to microaggregate and powder clay.There was no significant difference in aggregate carbon content and total nitrogen among different forest types,but in the same forest type,organic carbon and total nitrogen content vary form different size aggregates.The organic carbon and nitrogen contents decrease along with the decrease of aggregate size(2)Soil total organic carbon and total nitrogen content were affected by different litter inputs.Among the three forest types,the total organic carbon(TOC)in surface soil of natural forest and Pinus massoniana forest changed significantly under different litter treatments,and aboveground and underground litter input together significantly increased soil total organic carbon and nitrogen content.In natural forest,aboveground and underground litter input together increase soil total organic carbon.At the same time,increasing 2-5mm aggregate carbon content and promoting microaggregate agglomerate into 2-5mm aggregates,in Masson pine forest,aboveground and underground litter input together significantly increased soil total organic carbon,At the same time,increasing aggregates carbon content larger than 0.5mm and promoting microaggregate agglomerate into larger size aggregates.However,there was no significant increase in soil total organic carbon(TOC)in Cunninghamia lanceolata plantation under different litter treatments.in the early stage of litter input,the percentage of>5mm aggregate was increased by aboverground litter input,and in the latter stage of litter input,.aboveground litter input significantly increased the organic carbon content of>5mm aggregate and the percentage content of<0.053mm aggregate.(3)the relative contribution of litter to soil total organic carbon and aggregate organic carbon was different at different stages when litter was fed into soil.In natural forest,when litter was inputted for 6 months,the total organic carbon of soil mainly came from both aboveground and underground litters.The percentage of 0.053-0.25mm microaggregate organic carbon derived from underground litter was significantly higher than that from aboveground litter,and the total organic carbon of soil came from the common input of aboveground litter after 12 months of litter input.In Cunninghamia lanceolata plantation,in the early stage of litter input,aboveground litter contributed to soil total organic carbon(TOC).The aggregate organic carbon of 2-5mm in soil was mainly derived from aboveground litter in the later period of litter input,and the contribution of underground litter to soil total organic carbon was greater than that of aboveground litter.The aggregate organic carbon of 1-2mm in soil is mainly derived from underground litter.In Pinus massoniana forest,the proportion of soil total organic carbon derived from underground litter was always higher than that from aboveground litter,and the percentage of>5mm aggregate and 2-5mm in soil from underground litter was significantly higher than that from aboveground litter.(4)when different forest litter was imported into soil,the aggregate organic carbon was increased,while the aggregate organic carbon was protected from mineralization.In natural forest,both aboveground and underground litter input significantly increased the amount of organic carbon by<0.053mm aggregate compared with aboveground litter input,which was beneficial to the continuous accumulation of organic carbon in this particle size aggregate.In Cunninghamia lanceolata plantation,aboveground litter input is beneficial to increase 2-5mm aggregate organic carbon,and aboveground litter input significantly protects 0.053-0.25mm aggregate from mineralization compared with underground litter and aboveground litter.The falling matter input can improve the organic carbon of 1-2mm agglomerates.In Pinus massoniana forest,aboveground litter input significantly increased>5mm aggregate organic carbon content,and aboveground litter input significantly protected 1-2mm-1mm and<0.053mm aggregate organic carbon from mineralization compared with both aboveground and underground litter inputs.