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Large amounts of terrestrial organic C and N reserves lie in salt-affected environments, and their dynamics are not well understood.
This study was conducted to investigate how the contents and dynamics of ‘native’ organic C and N in sandy soils under different
plant species found in a salt-affected ecosystem were related to salinity and pH. Increasing soil pH was associated with significant
decreases in total soil organic C and C/N ratio; particulate (0.05–2 mm) organic C, N and C/N; and the C/N ratio in mineral-associated
(<0.05 mm) fraction. In addition, mineral-associated organic C and N significantly increased with an increase in clay content
of sandy soils. During 90-day incubation, total CO2-C production per unit of soil organic C was dependent on pH [CO2-C production (g kg−1 organic C) = 22.5 pH – 119, R
2 = 0.79]. Similarly, increased pH was associated with increased release of mineral N from soils during 10-day incubation.
Soil microbial biomass C and N were also positively related to pH. Metabolic quotient increased with an increase in soil pH,
suggesting that increasing alkalinity in the salt-affected soil favoured the survival of a bacterial-dominated microbial community
with low assimilation efficiency of organic C. As a result, increased CO2-C and mineral N were produced in alkaline saline soils (pH up to 10.0). This pH-stimulated mineralization of organic C and
N mainly occurred in particulate but not in mineral-associated organic matter fractions. Our findings imply that, in addition
to decreased plant productivity and the litter input, pH-stimulated mineralization of organic matter would also be responsible
for a decreased amount of organic matter in alkaline salt-affected sandy soils. 相似文献
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