microbial diversity of straw
Plant residues are one of the important sources of organic carbon (C) in agricultural soil. However, it is still unclear how nitrogen (N) status in farmland soil affects the organic C groups and its microbial mechanisms during plant residue decomposition. This study selected maize- (M) and potato-monoculture (P) soils with two N status (N0, unfertilized, and N2, 250 and 125 kg N ha-1 for M and P, respectively) as decomposition environments to conduct a 6-month decomposition of maize- (MS) and potato straw (PS). The results showed that soil N status had no significant effect decomposition rate of both straws, but changed the organic C groups for both straws. Alkyl C and aliphaticity increased for MS while decreased for PS at N2 relative to N0. The interaction between fungi-bacteria, and the abundance of recalcitrant C degradation genes (exoglucanase and chitinase) and enzyme activity (chitinase and sucrose) increased for MS, but decreased for PS at N2 as compared with N0. The structural equation model indicated that the increase of soil inorganic N reduced straw C/N, changed the microbial community structure and keystone in straw, enhanced enzyme activity, and thus altered the recalcitrant C content and the stability of organic C in decomposed straw. The results of this study emphasize the differential impact of soil N status on the chemical structure of different types of straw, as well as the coupling relationship between microbial communities and organic C chemical structure during the plant residue decomposition in farmland soil.