Background By removing and adding litter, the effects of litter treatment on soil active organic carbon and soil nutrients of Pinus koraiensis plantation and broad-leaved K.koraiensis forest were explored, which provided scientific basis and practical reference for sustainable management of the two forest types.

Methods In May 2018, the questions stated above were studied in Liangshui National Nature Reserve of Xiaoxing'an Mountains by setting up test plots, removing and adding litter, collecting and analyzing soil samples and data processing. The experiment was conducted to remove litter, add double litter and keep the original litter unchanged (control). Each treatment has three replicates. In May, August and October 2018, soil samples in 0-20 cm were collected in each test unit. Bring the soil sample back to the laboratory in time for processing.

Results In K.koraiensis plantation, litter removal treatment had significant effects on soil easily oxidized organic carbon, particulate organic carbon and light fraction carbon (P < 0.05). Adding litter treatment had no significant effects on soil easily oxidized organic carbon, but had significant effects on soil particulate organic carbon and light fraction carbon (P < 0.05). Litter treatment had no significant effect on soil easily oxidized organic carbon, but had significant effect on soil particulate organic carbon and light fraction carbon (P < 0.05). Adding litter treatment had no significant effect on soil easily oxidized organic carbon, but had significant effect on soil particulate organic carbon and light fraction carbon (P < 0.05). The effect of litter removal treatment on soil total organic carbon of two forest types was significant (P < 0.05), but the effect of litter addition treatment on soil total organic carbon was not significant; the effect of litter removal and litter addition treatment on soil total nitrogen and total phosphorus was not significant. The effects of litter removal and addition on soil C/N of K. pine plantation were not significant; the effects of litter removal on soil C/N of broad-leaved P.koraiensis plantation were significant (P < 0.05), but the effects of litter addition on soil C/N were not significant.

Conclusions In P. koraiensis plantation, adding litter treatment had no significant effect on soil easily oxidized organic carbon, while removing litter treatment had significant effect (P < 0.05) on soil easily oxidized organic carbon; in broad-leaved K. pine plantation, adding and removing litter treatment had no significant effect on soil easily oxidized organic carbon. In the two types of forest, the removal and addition treatments had significant effects (P < 0.05) on soil particulate organic carbon and light fraction carbon. In the two forest types, the effect of litter removal on soil total organic carbon was significant(P < 0.05), but the effect of litter addition was not significant; the effect of litter removal and litter addition on soil total nitrogen and total phosphorus was not significant.