Downward carbon transport in a 2000-year rice paddy soil chronosequence traced by radiocarbon measurements

Bräuer, Tino; Grootes, P. M.; Nadeau, Marie‐Josée; Andersen, Nils

doi:10.1016/j.nimb.2012.07.012

Cited by 14 publications

(16 citation statements)

References 25 publications

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“…The measured fulvic acids have, with 1 exception, a higher 14 C concentration than the humic acids. In P50, the striking drop in 14 C concentration across the plough pan (horizon Ardp), already observed for TOC (Bräuer et al 2013), is also seen in the chemical fractions (Figure 2a). The development of their 14 C concentrations with depth is very similar.…”

Section: Sample Treatment For Amssupporting

confidence: 55%

“…14 C values are stated in percent modern carbon (pMC) and were calculated from the measured 14 C/ 12 C ratios of the sample and the oxalic acid standard according to Stuiver and Polach (1977). Table 1 The 14 C concentrations of TOC (Bräuer et al 2013) and the 3 corresponding chemical fractions humin, humic acid, and fulvic acid are given as a function of depth for the 50-yr-old paddy (P50), non-paddy soil (NP50), and the 2000-yr-old paddy soil (P2000) in Figure 2a-c and Table 1, together with the values obtained for the sediment of the tidal flat. The results clearly show the age inhomogeneity of the TOC, with the insoluble humin fraction consistently older, and the more mobile humic acids younger than the TOC.…”

Section: Sample Treatment For Amsmentioning

confidence: 99%

“…The decrease is too large to be caused by natural decay, even in 2000 yr, which would reduce the 47.6 pMC of the deep tidal flat to 37.4 pMC. Instead, the low 14 C concentrations of the deep humin fractions may reflect the effect of a supply of fresh OC to a subsoil containing a mixture of organic material, in part old, reworked, and in part contemporaneous with the time of sedimentation (Bräuer et al 2013). With measured 14 C concentrations in the deep tidal flat close to 50 pMC, the contemporaneous fraction must be at least 50% of the bulk and humin OC.…”

Section: Sample Treatment For Amsmentioning

confidence: 99%

“…Paddy and non-paddy soils (upland soils not used for submerged rice cultivation) of different ages, developed on reclaimed estuarine sediments originating from the nearby Yangtze River, were sampled near Cixi in Zhejiang Province, China. Previous results of bulk soil samples documented the transport-induced development of TOC and 14 C depth gradients in the initially uniform upper 1 m of sediment, and demonstrated a replacement of old organic carbon by young OC by using the radioactive isotope 14 C as a tracer (Bräuer et al 2013). Water is the most likely transport medium, so a simple OC partition in acid/water soluble, alkali/ water soluble, and water insoluble was chosen to further evaluate OC transport.…”

Section: Introductionmentioning

confidence: 99%

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Origin of Subsoil Carbon in a Chinese Paddy Soil Chronosequence

Bräuer

2013

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ABSTRACT. Rice paddies are highly important agricultural soils in view of their relevance as major staple food provider in the world and their key role in the global carbon cycle, caused by special management practices. A soil chronosequence, consisting of paddy and upland soils, developed on reclaimed estuarine sediments in the Province of Zhejiang, China, was sampled to investigate the influence of duration of agricultural use (50 to 2000 yr) on soil composition. The uniform composition of the parent material provides the unique opportunity to compare the effects of different land management practices (paddy and non-paddy) on soil carbon dynamics and the origin of organic carbon (OC) in top-and subsoils, using 14 C measurements by accelerator mass spectrometry (AMS). The total soil organic carbon (TOC) was split into chemically defined pools of different mobility, namely the acid-and water-soluble fulvic acids (FA), the alkali-soluble humic acids (HA), and insoluble humin fraction. The more mobile HA and FA fractions contain significantly more 14 C than the corresponding TOC and humin, indicating a downward transport of OC in the subsoil. Plant roots with 14 C concentrations up to 128% of the modern standard, found far below the plough pan, reveal plant roots and root exudates as other direct sources of subsoil OC in paddy soils.

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Section: Sample Treatment For Amssupporting

confidence: 55%

Section: Sample Treatment For Amsmentioning

confidence: 99%

Section: Sample Treatment For Amsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Origin of Subsoil Carbon in a Chinese Paddy Soil Chronosequence

Bräuer

2013

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“…Therefore, it seems reasonable to assume that inherited BC from the marine sediment remained the dominant BC source in the subsoils. This assumption is in accordance with a lower 14 C concentration found for subsoil under paddy cultivation, which was interpreted as old organic carbon from Yangtze River deposits in the Bay of Hangzhou (Bräuer et al ., ; Kalbitz et al ., ). This assumption also accords with studies of Ziolkowski & Druffel () and Dittmar et al .…”

Section: Discussionmentioning

confidence: 98%

Black carbon accrual during 2000 years of paddy-rice and non-paddy cropping in the Yangtze River Delta, China

et al. 2014

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Rice straw burning has accompanied paddy management for millennia, introducing black carbon (BC) into soil as the residue of incomplete combustion. This study examined the contribution of BC to soil organic matter and the rate at which it accumulates in paddy soils as a result of prolonged paddy management. Soil depth profiles were sampled along a chronosequence of 0-2000 years of rice-wheat rotation systems and adjacent non-paddy systems (50-700 years) in the Bay of Hangzhou (Zhejiang province, China). The soil BC content and its degree of condensation were assessed using benzene-polycarboxylic acids (BPCAs) as geochemical markers. The results showed that despite regular long term BC input, BC only contributed 7-11% of total soil organic carbon (SOC) in the topsoil horizons. Nevertheless, along with SOC, paddy soils accumulated BC with increasing duration of management until 297 years to reach a steady-state of 13 t BC ha(-1). This was 1.8 times more than in non-paddy soils. The fate of BC in paddy soils (0-1 m) could be modeled revealing an average annual input of 44 kg ha(-1) yr(-1), and a mean residence time of 303 years. The subsoils contributed at least 50% to overall BC stocks, which likely derived from periods prior to land embankment and episodic burial of ancient topsoil, as also indicated by BPCA pattern changes. We conclude that there is a significant but limited accumulation of C in charred forms upon prolonged paddy management. The final contribution of BC to total SOC in paddy soils was similar to that in other aerobic ecosystems of the world.

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Spatial distribution of soil organic matter in two fields on tidal flat sediments (Zhejiang Province, China) differing in duration of paddy management

Kölbl

Mueller-Niggemann

Schwark

et al. 2015

J. Plant Nutr. Soil Sci.

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Despite of its ecological and economic importance, only limited information is available on spatial variability of soil organic C (OC) in paddy fields during soil development. To obtain deeper insights into the accumulation and spatial distribution of OC with ongoing paddy management, the present study investigates spatial heterogeneities in puddled topsoil layers, in the plough pan, as well as in the underlying subsoil of a 50-and 300-y old paddy site at the area of Cixi (Hangzhou Bay, E China). Sampling of the plots was done on the basis of a regular, orthogonal grid. The grid combined a large-scale design with distances of 5 m with a small-scale nested sampling ranging within 0.5 to 1 m. Samples have been taken with an auger in three sampling depths: (1) puddled topsoil layer, (2) dense plough layer, (3) mixed subsoil horizon. All samples were analyzed for their OC and total N concentrations as well as for their soil color (lightness value) to assess relationships between soil lightness and OC amount and distribution. The spatial behavior of all analyzed parameters in the different soil layers was investigated by calculating variograms; the degree of spatial dependence was determined by nugget-to-sill ratios. The results show that for each analyzed soil layer, OC and N concentrations were significantly higher in the field with 300 y of paddy management than in the field with 50 y of paddy management. Topsoil OC concentrations changed from 13.8 to 23.6 mg g -1 , OC in the plough layer changed from 3.3 to 9.6 mg g -1 , and also the subsoil showed a slight increase from 2.9 to 3.3 mg g -1 . Although only two points in time were compared, we assume that paddy soil formation is the most likely reason for differences in the spatial distribution of OC between the two sites. Comparing the spatial depth distribution of the 50-and 300-y old paddy sites suggests that the development of a spatial pattern of OC proceeded with time from topsoil to the underlying soil horizons. Measuring soil lightness was insufficient to predict amount and distribution of soil OC in paddy soils, especially in soils with interfering dark-colored burnt straw residues. The degree of spatial homogeneity was equal in the two sites, suggesting that cultivation practices (puddling, levelling, burning and incorporation of straw residues) most likely maintained a rather high random spatial variability of approx. 45%. The spatial pattern of OC in the topsoil was dissimilar to the plough layer, revealing that transport of OC in the plough pan occurred mainly in preferential flow paths along localized cracks and biopores.

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Downward carbon transport in a 2000-year rice paddy soil chronosequence traced by radiocarbon measurements

Cited by 14 publications

References 25 publications

Origin of Subsoil Carbon in a Chinese Paddy Soil Chronosequence

Origin of Subsoil Carbon in a Chinese Paddy Soil Chronosequence

Black carbon accrual during 2000 years of paddy-rice and non-paddy cropping in the Yangtze River Delta, China

Spatial distribution of soil organic matter in two fields on tidal flat sediments (Zhejiang Province, China) differing in duration of paddy management

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