水保所知识产出(1956---)知识库

Nitrogen (N) deposition affects soil organic carbon (SOC) decomposition, therefore altering the global terrestrial
carbon (C) cycle. However, it remains unclear how N deposition affects SOC decomposition by regulating mi-
crobial community composition and function, especially C-cycling functional gene composition. We investigated
the effects of N addition (0, 3, 6, and 9 g N m −2 y –1 ) on the composition of soil microbial C-cycling functional
gene, SOC-degrading enzyme activities, and CO 2 emissions in a Pinus tabulaeformis forest. Under low N addition
(3 or 6 g N m −2 y –1 ), labile C-degradation gene abundances were significantly increased. Under high N addition
(9 g N m −2 y –1 ), C-cycling functional gene abundance and diversity were significantly decreased. These effects
were related to the changes in soil NO 3
– -N, dissolved organic C, total N, and microbial biomass C contents.
Furthermore, low N addition stimulated the activities of SOC-degrading enzyme and CO 2 emissions, whereas
high N addition had the inhibitory effect. C-degradation gene abundances were significantly correlated with the
SOC-degrading enzyme activities and CO 2 emissions. Increase in CO 2 emission rates were related to the high
microbial functional potentials for labile C degradation under low N addition, whereas the lower CO 2 emission
rates were related to the low microbial functional potentials for labile as well as recalcitrant C degradation under
high N addition. Our study indicated that N deposition may change SOC decomposition by altering the abun-
dance of labile C and recalcitrant C degradation genes.