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Does metal pollution matter with C retention by rice soil?

Bian R, Cheng K, Zheng J, Liu X, Liu Y, Li Z, Li L, Smith P, Pan G, Crowley D, Zheng J, Zhang X, Zhang L, Hussain Q - Sci Rep (2015)

Bottom Line: Soil respiration, resulting in decomposition of soil organic carbon (SOC), emits CO2 to the atmosphere and increases under climate warming.Here we show significantly increased soil respiration and efflux of both CO2 and CH4 with a concomitant reduction in SOC storage from a metal polluted rice soil in China.The pollution-induced increase in soil respiration and loss of SOC storage will likely counteract efforts to increase SOC sequestration in rice paddies for climate change mitigation.

View Article: PubMed Central - PubMed

Affiliation: Institute of Resource, Ecosystem and Environment of Agriculture, Nanjing Agricultural University, Nanjing 210095-China.

ABSTRACT
Soil respiration, resulting in decomposition of soil organic carbon (SOC), emits CO2 to the atmosphere and increases under climate warming. However, the impact of heavy metal pollution on soil respiration in croplands is not well understood. Here we show significantly increased soil respiration and efflux of both CO2 and CH4 with a concomitant reduction in SOC storage from a metal polluted rice soil in China. This change is linked to a decline in soil aggregation, in microbial abundance and in fungal dominance. The carbon release is presumably driven by changes in carbon cycling occurring in the stressed soil microbial community with heavy metal pollution in the soil. The pollution-induced increase in soil respiration and loss of SOC storage will likely counteract efforts to increase SOC sequestration in rice paddies for climate change mitigation.

No MeSH data available.


A proposed engine of soil C cycling modified in metal polluted rice paddy.The figure indicate the processes associated under metal stress, giving rise to an overall reduction in C storage with decline in crop productivity and thus increase in global warming potential (GWP) from rice production.
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f2: A proposed engine of soil C cycling modified in metal polluted rice paddy.The figure indicate the processes associated under metal stress, giving rise to an overall reduction in C storage with decline in crop productivity and thus increase in global warming potential (GWP) from rice production.

Mentions: The decrease in SOC here is linked to a reduction not only in microbial abundance, but a decline in fungal-to-bacterial ratio in PF plots over BG plots (Table 2). This change is consistent with our previous finding of a cross site study of metal-polluted rice croplands from South China26. Cotrufo et al.11 reported a similar microbial community change with forest soils but with decreased respiratory C loss. Fungi-dominated microbial communities have been known to lower SOM decomposition rates in C cycling studies827, and in experiments with long term fertilization trails26 and with heavy metal affected soils1113. In this study, nevertheless, the stressed microbial community change is characterized by a significant lower F/B ratio across different assays. Fungi in soil contribute to building-up large sized micro-aggregates28, and the reduction in cultivable fungi community could induce a decrease of large sized micro-aggregates, which has been observed in the polluted fields as shown in Table 1. As well known, soil organic matter can be physically protected with aggregates with the process inhibiting microbial access to the organic substrate2930. Furthermore, large sized micro-aggregates play an important role in SOC sequestration, which have been shown in maize fields under tillage experiments from the USA31, and in rice paddies under long term organic/inorganic combined fertilization experiments32. This study indicates a marked decrease in the proportion of large sized micro-aggregates in heavy metal polluted soils (Table 1). Here, a combination of increased metabolic respiration and decreased physical protection could explain the overall increased soil respiration and in turn, the significant reduction in SOC storage due to enhanced SOC decomposition under metal pollution. Thus, we propose a modified engine as a mechanism for changes in biogenic processes of C cycling, with a decline in fungal dominance of the stressed soil microbial community driven by metal pollution in the rice soil (Fig. 2).


Does metal pollution matter with C retention by rice soil?

Bian R, Cheng K, Zheng J, Liu X, Liu Y, Li Z, Li L, Smith P, Pan G, Crowley D, Zheng J, Zhang X, Zhang L, Hussain Q - Sci Rep (2015)

A proposed engine of soil C cycling modified in metal polluted rice paddy.The figure indicate the processes associated under metal stress, giving rise to an overall reduction in C storage with decline in crop productivity and thus increase in global warming potential (GWP) from rice production.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4536517&req=5

f2: A proposed engine of soil C cycling modified in metal polluted rice paddy.The figure indicate the processes associated under metal stress, giving rise to an overall reduction in C storage with decline in crop productivity and thus increase in global warming potential (GWP) from rice production.
Mentions: The decrease in SOC here is linked to a reduction not only in microbial abundance, but a decline in fungal-to-bacterial ratio in PF plots over BG plots (Table 2). This change is consistent with our previous finding of a cross site study of metal-polluted rice croplands from South China26. Cotrufo et al.11 reported a similar microbial community change with forest soils but with decreased respiratory C loss. Fungi-dominated microbial communities have been known to lower SOM decomposition rates in C cycling studies827, and in experiments with long term fertilization trails26 and with heavy metal affected soils1113. In this study, nevertheless, the stressed microbial community change is characterized by a significant lower F/B ratio across different assays. Fungi in soil contribute to building-up large sized micro-aggregates28, and the reduction in cultivable fungi community could induce a decrease of large sized micro-aggregates, which has been observed in the polluted fields as shown in Table 1. As well known, soil organic matter can be physically protected with aggregates with the process inhibiting microbial access to the organic substrate2930. Furthermore, large sized micro-aggregates play an important role in SOC sequestration, which have been shown in maize fields under tillage experiments from the USA31, and in rice paddies under long term organic/inorganic combined fertilization experiments32. This study indicates a marked decrease in the proportion of large sized micro-aggregates in heavy metal polluted soils (Table 1). Here, a combination of increased metabolic respiration and decreased physical protection could explain the overall increased soil respiration and in turn, the significant reduction in SOC storage due to enhanced SOC decomposition under metal pollution. Thus, we propose a modified engine as a mechanism for changes in biogenic processes of C cycling, with a decline in fungal dominance of the stressed soil microbial community driven by metal pollution in the rice soil (Fig. 2).

Bottom Line: Soil respiration, resulting in decomposition of soil organic carbon (SOC), emits CO2 to the atmosphere and increases under climate warming.Here we show significantly increased soil respiration and efflux of both CO2 and CH4 with a concomitant reduction in SOC storage from a metal polluted rice soil in China.The pollution-induced increase in soil respiration and loss of SOC storage will likely counteract efforts to increase SOC sequestration in rice paddies for climate change mitigation.

View Article: PubMed Central - PubMed

Affiliation: Institute of Resource, Ecosystem and Environment of Agriculture, Nanjing Agricultural University, Nanjing 210095-China.

ABSTRACT
Soil respiration, resulting in decomposition of soil organic carbon (SOC), emits CO2 to the atmosphere and increases under climate warming. However, the impact of heavy metal pollution on soil respiration in croplands is not well understood. Here we show significantly increased soil respiration and efflux of both CO2 and CH4 with a concomitant reduction in SOC storage from a metal polluted rice soil in China. This change is linked to a decline in soil aggregation, in microbial abundance and in fungal dominance. The carbon release is presumably driven by changes in carbon cycling occurring in the stressed soil microbial community with heavy metal pollution in the soil. The pollution-induced increase in soil respiration and loss of SOC storage will likely counteract efforts to increase SOC sequestration in rice paddies for climate change mitigation.

No MeSH data available.