Global Change Biology, November 2011, Vol.17(11), pp.3405-3417
Lowland rice paddy soils may accumulate significant amounts of organic matter. Our aim was to investigate the role of prolonged paddy management on the nitrogen () status of the soils, and to elucidate the contribution of bacteria and fungi to long‐term accumulation processes. For this purpose, we sampled a chronosequence of 0–2000 years of rice cropping with adjacent non‐paddy systems in the ay of angzhou, hina. The samples were analyzed for bulk density, total, mineral and microbial (), and amino sugars as markers for microbial residues. The results showed that during the first 100 years of land embankment, both paddy and non‐paddy soils accumulated at a rate of up to 61 and 77 kg ha per annum, reaching steady‐state conditions after 110–172 years, respectively. Final stocks in paddy fields exceeded those of the non‐paddies by a factor of 1.3. The contribution of amino sugars to total increased to a maximum of 34 g kg in both land‐use systems, highlighting a significant accumulation of in microbial residues of the surface soils. Correspondingly, the ratio of to microbial residue‐ decreased to a constant value. In the paddy subsoils, we found that bacterial residues particularly contributed to the pool of microbial residue‐. Nevertheless, the absolute contents of amino sugars in paddy subsoils decreased during the last 1700 years of the chronosequence. We conclude that under paddy cultivation, soil microorganisms may accumulate parts of this in their residues despite low overall availability. However, this accumulation is limited to initial stages of paddy soil development and restricted to the surface horizons, thus challenging its sustainability with future land‐use changes.
Amino Sugars ; Cultivation Chronosequence ; Microbial Biomass ; Nitrogen Accumulation ; Paddy Soil