Agroforestry alters the fluxes of greenhouse gases of Moso bamboo plantation soil

Abstract

Agroforestry systems are widely applied in China and have both economic and ecological benefits. However, relatively few prior studies have investigated the relative ecological benefits of various agroforestry systems. In the present study, the static chamber method, quantitative polymerase chain reaction, high throughput sequencing were used to establish the differences in greenhouse gases (GHGs) fluxes and explore the bacterial and fungal populations affecting GHGs fluxes under different agroforestry systems, including pure Moso bamboo forest (CK), bamboo + Bletilla striata (BB), bamboo + Dictyophora indusiata (BD), and bamboo + chickens (BC). The highest cumulative CH _4 uptake and N _2 O emission in spring occurred in BB while the highest cumulative CO _2 emission and global warming potential (GWP) in spring occurred in BC. The Methylomirabilaceae were the key methanotrophs influencing the comparative differences in NO _3 ^− associated CH _4 uptake among the various agroforestry systems. N _2 O emission was associated with pH, and nitrifiers such as the ammonia-oxidizing archaea and bacteria (Nitrospiraceae and Nitrosomonadaceae) rather than denitrifiers may be the key microbes affecting N _2 O emission in different agroforestry systems. The bacteria Actinobacteriota and Fibrobacteres and the fungi Ascomycetes and Basidiomycota were the primary microbial taxa influencing CO _2 emission. The lignin-decomposing Basidiomycota played more important roles in CO _2 emission than the cellulose-decomposing fungi and bacteria under the various agroforestry systems. CO _2 emission was positively correlated with NO _3 ^− in the bacterial community and was negatively correlated with NO _3 ^− in the fungal community, implying two C decomposition mechanisms caused by denitrification dominated in bacteria and those caused by microbial nitrogen mining dominated in fungi. The foregoing results suggested that bamboo + B. striata had comparatively higher ecological benefits as it is associated with low GWP and external C fixation. The present study provided valuable information for screening bamboo-based agroforestry systems with high ecological benefits. It also elucidated the microbial mechanism explaining the observed differences in GHGs fluxes between the various agroforestry systems.

Keywords

• agroforestry
• bacterial community
• carbon cycle
• fungal community
• greenhouse gases
• Moso bamboo