Long-term rice cultivation stabilizes soil organic carbon and promotes soil microbial activity in a salt marsh derived soil chronosequence

Abstract

Soil organic carbon (SOC) sequestration with enhanced stable carbon storage has been widely accepted as a very important ecosystem property. Yet, the link between carbon stability and bio-activity for ecosystem functioning with OC accumulation in field soils has not been characterized. We assessed the changes in microbial activity versus carbon stability along a paddy soil chronosequence shifting from salt marsh in East China. We used mean weight diameter, normalized enzyme activity (NEA) and carbon gain from straw amendment for addressing soil aggregation, microbial biochemical activity and potential C sequestration, respectively. In addition, a response ratio was employed to infer the changes in all analyzed parameters with prolonged rice cultivation. While stable carbon pools varied with total SOC accumulation, soil respiration and both bacterial and fungal diversity were relatively constant in the rice soils. Bacterial abundance and NEA were positively but highly correlated to total SOC accumulation, indicating an enhanced bio-activity with carbon stabilization. This could be linked to an enhancement of particulate organic carbon pool due to physical protection with enhanced soil aggregation in the rice soils under long-term rice cultivation. However, the mechanism underpinning these changes should be explored in future studies in rice soils where dynamic redox conditions exist.

Methanogenic abundance and changes in community structure along a rice soil chronosequence from east China

“…Archaeal communities are generally considered to be quite stable and resistant to short‐term environmental variation (Conrad et al ., ). Similar to changes in the diversity of bacterial and fungal communities in previous studies (Liu et al ., 2016; Wang et al ., ), the Shannon index of both archaeal and methanogenic archaeal communities increased shortly after the change to rice cultivation. This was observed for the 50‐year‐old site and it did not change thereafter along the chronosequence.…”

“…The scale bar represents 0.05 substitutions per nucleotide. 2016; Wang et al, 2015), the Shannon index of both archaeal and methanogenic archaeal communities increased shortly after the change to rice cultivation. This was observed for the 50-year-old site and it did not change thereafter along the chronosequence.…”

“…The soil samples studied were along a chronosequence of soils under rice cultivation that were derived from a tidal marsh in the coastal area of Cixi City, Zhejiang, China (30 ∘ 05 ′ -30 ∘ 19 ′ N, 121 ∘ 09 ′ -121 ∘ 31 ′ E) (Figure 1); they have already been described in detail by Wang et al (2015). This area has a typical northern subtropical monsoon climate, with a mean annual temperature of 16.3 ∘ C and annual precipitation of 1325 mm.…”

“…Methods used to measure soil properties followed those that have been described in detail by Wang et al (2015). Soil pH was determined in a suspension of soil and water, a mass ratio of 1:5, with a pH meter (Mettler Toledo Seveneasy, Switzerland).…”

“…() found an increasing potential for methanotrophic activity and unchanged community composition with prolonged rice cultivation for up to 2000 years. In a recent study of a similar sequence, we reported an increase in microbial abundance and activity, but not microbial diversity, with the accumulation and stabilization of soil organic matter under long‐term rice cultivation (Wang et al ., ). It is still uncertain, however, how the species composition and abundance of archaea, in particular methanogenic archaea, change in response to soil development as soil organic matter (SOM) accumulates and stabilizes following prolonged rice cultivation.…”