ena-STUDY-CHINESE ACADEMY OF SCIENCES-26-03-2015-09:05:07:189-100
Nitrogen  fertilization  directly  affects  soil  bacterial  diversity  and  indirectly  affects  bacterial community composition through soil acidification and plant community changes in grassland
Nitrogen  (N)  deposition  influences  both  above-  and  belowground  communities  and  influences  ecosystem  functioning.  However  the  mechanisms  underlying  alternations  in  bacterial  communities  following  N  enrichment  remain  elusive,  as  does  an  integrated  understanding  of  plant-soil-microbe interactions. In this study, the responses of soil bacterial community composition and diversity to N enrichment  were  investigated  at  surface  (0-10 cm)  and  sub-surface  (10-20 cm)  soils  in a  temperate  steppe  ecosystem.  N  addition  (>120  kg  N  ha -1   yr -1 )  resulted  in  a  significant  shift  in  bacterial community  composition  and  a  decrease  in  bacterial  diversity  in  surface  soil,  but  the  effect  on  the sub-surface  layer  was  far  less  pronounced,  even  at  the  highest  addition  rate  (240  kg  N  ha -1   yr -1 ). Bacterial  community  composition  was  significantly  correlated  with  soil  and  plant  characteristics. Hierarchical structural equation modeling showed that soil ammonium availability was responsible for the shift in bacterial richness, whereas alternation in soil pH and plant composition contributed to the change in bacterial communities. Our results suggest that N fertilization directly affects soil bacterial richness  and  indirectly  affects  bacterial  communities  via  soil  acidification  and  changes  in  plant composition. This indicates that N addition in a temperate steppe ecosystem influences soil bacterial diversity and community composition in an inconsistent manner.
Nitrogen  (N)  deposition  influences  both  above-  and  belowground  communities  and  influences  ecosystem  functioning.  However  the  mechanisms  underlying  alternations  in  bacterial  communities  following  N  enrichment  remain  elusive,  as  does  an  integrated  understanding  of  plant-soil-microbe interactions. In this study, the responses of soil bacterial community composition and diversity to N enrichment  were  investigated  at  surface  (0-10 cm)  and  sub-surface  (10-20 cm)  soils  in a  temperate  steppe  ecosystem.  N  addition  (>120  kg  N  ha -1   yr -1 )  resulted  in  a  significant  shift  in  bacterial community  composition  and  a  decrease  in  bacterial  diversity  in  surface  soil,  but  the  effect  on  the sub-surface  layer  was  far  less  pronounced,  even  at  the  highest  addition  rate  (240  kg  N  ha -1   yr -1 ). Bacterial  community  composition  was  significantly  correlated  with  soil  and  plant  characteristics. Hierarchical structural equation modeling showed that soil ammonium availability was responsible for the shift in bacterial richness, whereas alternation in soil pH and plant composition contributed to the change in bacterial communities. Our results suggest that N fertilization directly affects soil bacterial richness  and  indirectly  affects  bacterial  communities  via  soil  acidification  and  changes  in  plant composition. This indicates that N addition in a temperate steppe ecosystem influences soil bacterial diversity and community composition in an inconsistent manner.