• Authors:
    • Jiang, M.
    • Lu, X.-G.
    • Zhang, Y.
    • Dong, G.-H.
    • Liu, X.-H.
  • Source: CLEAN – Soil, Air, Water
  • Volume: 41
  • Issue: 4
  • Year: 2013
  • Summary: Based on the estimation of greenhouse gases (GHG) emissions and carbon sequestration of the total conversion of marshlands (TMC), marshlands conversion to paddy fields (MCPFs) and marshlands conversion to uplands (MCULs), this study revealed the contribution to the global warming mitigation (CGWM) of paddy fields versus uplands converted from marshlands in the Sanjiang Plain (excluding the Muling-Xingkai Plain on south of Wanda Mountain), Heilongjiang Province, northeast China. The results showed that the total area of MCPFs and MCULs was 504.23x103ha between 1982 and 2005. The CGWM per unit area was 45.53t CO2eq/ha for MCPFs and that was 23.95t CO2eq/ha for MCULs, with an obvious 47.40% reduction. The MCPFs and MCULs ecosystems acted as the carbon sink all of the year. As far as CGWM per unit area is concerned, MCPFs mitigated the greenhouse effect which was greater than MCULs. And it was effective that the implementation of the uplands transformed into paddy fields in Northeast China with regard to marshlands protection and croplands (including paddy fields and uplands) reclamation.
  • Authors:
    • Mao, Y. L.
    • Zhang, L. M.
    • Long, J.
    • Xing, S. H.
  • Source: Acta Pedologica Sinica
  • Volume: 50
  • Issue: 4
  • Year: 2013
  • Summary: No matter whether a farmland ecosystem acts as source or sink of global greenhouse gases, it has an important impact on annual variation of the concentration of carbon dioxide in the atmosphere. In this study, four counties, namely Minhou, Pucheng, Tongan and Yongding, located in different geographical locations in Fujian Province, subtropical China, were selected as typical study zones. Based on the data of field measurements at 23 869 sampling site in 1982 and 12 521 sampling sites in 2008, scattered in these four counties, a 1:50 000 database of soil type-land use pattern was established, analysis was carried out of changes in organic carbon density in the farmlands of Fujian in the past 30 years as affected by group, sub-group, genus and land use of the soils, and estimation was done of the soil organic carbon storages in the farmlands of the province in these two historical periods, using the scaling up method. Results show that the farmlands in Fujian as a whole acted as a weak carbon sink in the past 30 years, with carbon density and carbon storage increased by C 0.24 kg m -2 and 4.26 Tg, respectively. Contribution of the farmland ecosystems to the "carbon sink/source" varied sharply with soil type and landuse pattern. When speaking of soil types, purplish soil, acid purplish soil and calcic mud field contributed the greatest to the "carbon sink" in soil group, soil subgroup and soil genu, respectively, with organic carbon density increased by C 0.63, 0.63 and 1.25 kg m -2, respectively; while coastal solonchaks, coastal solonchaks and yellow sandy soil were the major contributors to the "carbon source" in soil group, soil subgroup and soil genu, respectively, with organic carbon density decreased by C 0.59, 0.59 and 1.08 kg m -2, respectively. In terms of land use, irrigated paddy fields were the major carbon sink in the province with organic carbon density increased by C 0.27 kg m -2; while irrigated uplands the main carbon source with organic carbon density decreased by C 0.36 kg m -2. The findings suggest that in formulating policies for management of soil organic carbon in farmlands of Fujian in the years to come, priority should be given to effective management measures for the types of soils and the patterns of land use that are large in area and cause organic carbon density to decrease.
  • Authors:
    • Tian, H.
    • Lu, C.
  • Source: Global Change Biology
  • Volume: 19
  • Issue: 2
  • Year: 2013
  • Summary: Increasing reactive nitrogen (N) input has been recognized as one of the important factors influencing climate system through affecting the uptake and emission of greenhouse gases (GHG). However, the magnitude and spatiotemporal variations of N-induced GHG fluxes at regional and global scales remain far from certain. Here we selected China as an example, and used a coupled biogeochemical model in conjunction with spatially explicit data sets (including climate, atmospheric CO2, O-3, N deposition, land use, and land cover changes, and N fertilizer application) to simulate the concurrent impacts of increasing atmospheric and fertilized N inputs on balance of three major GHGs (CO2, CH4, and N2O). Our simulations showed that these two N enrichment sources in China decreased global warming potential (GWP) through stimulating CO2 sink and suppressing CH4 emission. However, direct N2O emission was estimated to offset 39% of N-induced carbon (C) benefit, with a net GWP of three GHGs averaging -376.3 +/- 146.4 Tg CO2 eq yr(-1) (the standard deviation is interannual variability of GWP) during 2000-2008. The chemical N fertilizer uses were estimated to increase GWP by 45.6 +/- 34.3 Tg CO2 eq yr(-1) in the same period, and C sink was offset by 136%. The largest C sink offset ratio due to increasing N input was found in Southeast and Central mainland of China, where rapid industrial development and intensively managed crop system are located. Although exposed to the rapidly increasing N deposition, most of the natural vegetation covers were still showing decreasing GWP. However, due to extensive overuse of N fertilizer, China's cropland was found to show the least negative GWP, or even positive GWP in recent decade. From both scientific and policy perspectives, it is essential to incorporate multiple GHGs into a coupled biogeochemical framework for fully assessing N impacts on climate changes.
  • Authors:
    • Shang, Z. H.
    • Chen, X. P.
    • Pan, J. L.
    • Dai, W. A.
    • Wang, X. M.
    • Ma, L. N.
    • Guo, R. Y.
  • Source: Chinese Journal of Eco-Agriculture
  • Volume: 21
  • Issue: 11
  • Year: 2013
  • Summary: Soil carbon and nitrogen in vegetable fields are the core elements of soil quality and environmental pollution. The decrease of soil C/N ratio of vegetable fields under greenhouse conditions causes an imbalance in soil carbon and nitrogen content. An effective way of adjusting soil carbon and nitrogen conditions in vegetable fields has been by improving soil quality and decreasing environmental pollution. Furthermore, there has been little research on soil carbon and nitrogen mineralization under greenhouse conditions in the Tibetan region. After transformations of alpine meadows and farmlands into solar greenhouse vegetable fields, there was the need to study the characteristics and processes of soil mineralization. In this study therefore, carbon and nitrogen mineralization in soils of alpine grassland, farmland and greenhouse (1-year, 5-year) were analyzed in an indoor incubation experiment. The results showed that soil carbon mineralization in different soil types mainly occurred during the first seven days (0-7 d) after treatment. Soil carbon mineralization was higher under alpine grassland than in farmland and 5-year greenhouse conditions ( P0.05). This was attributed to soil nutrient and soil microbial environment sensitivity to temperature. Soil CO 2-C accumulation in farmland soil was higher than in alpine grassland soil. It was also higher in alpine grassland soil than in the 1-year greenhouse and 5-year greenhouse soils. However, the differences in soil organic carbon mineralization and accumulation among alpine grassland, farmland, 1-year greenhouse and 5-year greenhouse soil conditions were not significant ( P>0.05) at 28 days after treatment. Soil nitrogen mineralization mainly happened in different soil types during the first three days (3 d) after treatment. With delayed incubation, the main process of soil nitrogen mineralization was nitrogen fixation. Soil inorganic nitrogen content in alpine grassland, farmland, 1-year greenhouse and 5-year greenhouse soils at 28 days after incubation were 29.04%, 75.94%, 66.86% and 65.70% of that at 0 day, respectively. The results showed that soil nitrogen mineralization capacity of alpine grassland soil was stronger than farmland, 1-year greenhouse and 5-year greenhouse soils. Soil nitrogen mineralization capacity of farmland was weaker than alpine grassland, 1-year greenhouse and 5-year greenhouse. Also soil nitrogen mineralization capacities of 1-year greenhouse and 5-year greenhouse were similar. Moreover, soil mineralization processes were similar among different soil conditions.
  • Authors:
    • Xie, D. T.
    • Shi, S.
    • Liu, Y. Y.
    • Li, J. Q.
    • Ni, J. P.
    • Huang, A. Y.
    • Mu, Z. J.
    • Hatano, R.
  • Source: Journal of Soil Science and Plant Nutrition
  • Volume: 13
  • Issue: 3
  • Year: 2013
  • Summary: Vegetable fields in China are characterized with intensive fertilization and cultivation, and their net effect on the global warming deserves attention. Greenhouse gas fluxes were thus measured, using a static closed chamber method, over approximately 18 months in two typical subtropical vegetable fields with different soil types and contrasting soil properties. Five consecutive crops were planted in one field and four in the other. Intensive fertilization consistently stimulated soil N2O emission, while imposed complicated impact on soil respiration with CO2 emission enhanced in one field and suppressed in the other field. The fertilizer-induced N2O emission factors (EFs) varied with individual crop phases and averaged 1.4 to 3.1% across the whole sampling period for different fields. The interaction of soil temperature and moisture could explain about 58% of the seasonal variation in the EFs. All the soils under different vegetable cropping systems were net sources of atmospheric radiative forcing and the net global warming potential over the entire study period ranged from 1,786 to 3,569 g CO2 equivalence m(-2) for fertilized soils with net CO2 emission contributing 53 to 67% and N2O emission occupying the remaining 33 to 47%.
  • Authors:
    • Ouyang, W.
    • Qi, S.
    • Hao, F.
    • Wang, X.
    • Shan, Y.
    • Chen, S.
  • Source: Ecological Modelling
  • Volume: 252
  • Year: 2013
  • Summary: Agricultural activity is a primary factor contributing to global warming. In higher latitude freeze zone, agricultural activities pose a more serious threat to global warming than other zones. The crop management practices of various land use types have direct impacts on soil organic carbon (SOC) and global warming potential (GWP). Crop variations and cultivation practices are two important factors affecting carbon sequestration and the exchange of greenhouse gases between soils and the atmosphere. This exchange has special characteristics in the freeze zone. In this paper, the impact of crop patterns and cultivation management (i.e., residue return rate, manure amendment, and chemical N fertiliser application) on SOC and GWP in an agricultural freeze zone was analysed. The Denitrification-Decomposition (DNDC) model was employed to predict the long-term dynamics of nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4) for diyland and paddy rice systems. The CO2-equivalent index was used to express the GWP response of N2O, CH4 and CO2. The simulated results indicated that the manure amendment and N fertiliser application can improve the SOC, increase crop production and enhance the GWP. The cultivation of returning residue to the soil is the win-win solution for SOC conservation and GWP control. It was found that paddy rice was preferable to dryland for sequestering atmospheric CO2 and mitigating global warming. This analysis also indicated that the DNDC model is a valid tool for predicting the consequences of SOC and GWP changes in cropland agroecosystems in the freeze zone. (C) 2012 Elsevier B.V. All rights reserved.
  • Authors:
    • Xu, J.
    • Ostwald, M.
    • Moberg, J.
    • Persson, M.
  • Source: Journal of Environmental Management
  • Volume: 126
  • Year: 2013
  • Summary: The Grain for Green Programme (GGP) was launched in China in 1999 to control erosion and increase vegetation cover. Budgeted at USD 40 billion, GGP has converted over 20 million hectares of cropland and barren land into primarily tree-based plantations. Although GGP includes energy forests, only a negligible part (0.6%) is planted as such, most of the land (78%) being converted for protection. Future use of these plantations is unclear and an energy substitution hypothesis is valid. We estimate the overall carbon sequestration via GGP using official statistics and three approaches, based on i) net primary production, ii) IPCC's greenhouse gas inventory guidelines, and iii) mean annual increment. We highlight uncertainties associated with GGP and the estimates. Results indicate that crop- and barren-land conversion sequestered 222-468 Mt of carbon over GGP's first ten years, the IPCC approach yielding the highest estimate and the other two approaches yielding similar but lower estimates (approximately 250 Mt of carbon). The carbon stock in these plantation systems yields a mean of 12.3 t of carbon per hectare. Assessment uncertainties concern the use of growth curves not designed for particular species and locations, actual plantation survival rates, and discrepancies in GGP figures (e.g., area, type, and survival rate) at different authority levels (from national to local). The carbon sequestered in above- and below-ground biomass from GGP represents 14% (based on the median of the three approaches) of China's yearly (2009) carbon dioxide emissions from fossil fuel use and cement production.
  • Authors:
    • Halberg, N.
    • Hermansen, J E.
    • Knudsen, M T.
    • Petersen, B M.
  • Source: Journal of Cleaner Production
  • Volume: 52
  • Year: 2013
  • Summary: Globally, soil carbon sequestration is expected to hold a major potential to mitigate agricultural greenhouse gas emissions. However, the majority of life cycle assessments (LCA) of agricultural products have not included possible changes in soil carbon sequestration. In the present study, a method to estimate carbon sequestration to be included in LCA is suggested and applied to two examples where the inclusion of carbon sequestration is especially relevant: 1) Bioenergy: removal of straw from a Danish soil for energy purposes and 2) Organic versus conventional farming: comparative study of soybean production in China. The suggested approach considers the time of the soil CO2 emissions for the LCA by including the Bern Carbon Cycle Model. Time perspectives of 20,100 and 200 years are used and a soil depth of 0-100 cm is considered. The application of the suggested method showed that the results were comparable to the IPCC 2006 tier I approach in a time perspective of 20 year, where after the suggested methodology showed a continued soil carbon change toward a new steady state. The suggested method estimated a carbon sequestration for the first example when storing straw in the soil instead of using it for bioenergy of 54, 97 and 213 kg C t(-1) straw C in a 200, 100 and 20 years perspective, respectively. For the conversion from conventional to organic soybean production, a difference of 32, 60 or 143 kg soil C ha(-1) yr(-1) in a 200,100 or 20 years perspective, respectively was found. The study indicated that soil carbon changes included in an LCA can constitute a major contribution to the total greenhouse gas emissions per crop unit for plant products. The suggested approach takes into account the temporal aspects of soil carbon changes by combining the degradation and emissions of CO2 from the soil and the following decline in the atmosphere. Furthermore, the results from the present study highlights that the choice of the time perspective has a huge impact on the results used for the LCA. For comparability with the calculation of the global warming potential in LCA, it is suggested to use a time perspective of 100 years when using the suggested approach for soil carbon changes in LCA. (C) 2013 Elsevier Ltd. All rights reserved.
  • Authors:
    • Streck, T.
    • Bisharat, R.
    • Stange, C. F.
    • Guo, Z.-D.
    • Ingwersen, J.
    • Ju, X.-T.
    • Qiu, S.-J.
    • Christie, P.
    • Zhang, F.-S.
  • Source: Pedosphere
  • Volume: 23
  • Issue: 2
  • Year: 2013
  • Summary: Excessive amounts of nitrate have accumulated in many soils on the North China Plain due to the large amounts of chemical N fertilizers or manures used in combination with low carbon inputs. We investigated the potential of different carbon substrates added to transform soil nitrate into soil organic N (SON). A 56-d laboratory incubation experiment using the N-15 tracer ((KNO3)-N-15) technique was carried out to elucidate the proportion of SON derived from accumulated soil nitrate following amendment with glucose or maize straw at controlled soil temperature and moisture. The dynamics and isotopic abundance of mineral N (NO3- and NH4+) and SON and greenhouse gas (N2O and CO2) emissions during the incubation were investigated. Although carbon amendments markedly stimulated transformation of nitrate to newly formed SON, this was only a substitution effect of the newly formed SON with native SON because SON at the end of the incubation period was not significantly different (P > 0.05) from that in control soil without added C. At the end of the incubation period, amendment with glucose, a readily available C source, increased nitrate immobilization by 2.65 times and total N2O-N emission by 33.7 times, as compared with maize straw amendment. Moreover, the differences in SON and total N2O-N emission between the treatments with glucose and maize straw were significant (P 0.05) greater than that in the control. Straw amendment may be a potential option in agricultural practice for transformation of nitrate N to SON and minimization of N2O emitted as well as restriction of NO3-N leaching.
  • Authors:
    • Wang, Y. Y.
    • Dong, W. X.
    • Zhang, X. Y.
    • Hu, C. S.
    • Zhang, Y. M.
    • Song, L. N.
    • Qin, S. P.
  • Source: Zhongguo Shengtai Nongye Xuebao / Chinese Journal of Eco-Agriculture
  • Volume: 21
  • Issue: 3
  • Year: 2013
  • Summary: Comprehensive studies on greenhouse gas emissions and the related global warming potential (GWP) under different agricultural management practices had the benefits of mitigated greenhouse gas emissions, reduced GWP and strengthened theoretical basis for measurements of greenhouse gas emissions. Based on experiment with four agricultural management patterns (T1: conventional pattern; T2: high-yield and high-efficiency pattern; T3: super-high-yield pattern; T4: super-high-yield, high-efficiency and soil fertility improvement pattern), N 2O, CO 2 and CH 4 fluxes in winter-wheat fields were monitored from October 2009 to September 2011 using the static chamber method and the gas chromatographic technique. Total greenhouse gas emissions and GWP were then accordingly estimated. The results indicated that the winter-wheat field was the sources of N 2O and CO 2, but the sink of CH 4. The effects of the different agricultural management patterns on the different greenhouse gas sources and sinks were different. High N application and sufficient irrigation increased the CO 2 and N 2O in the soil and strengthened the characteristics of soil as the emission source of CO 2 and N 2O. Meanwhile, CH 4 oxidation in soils was restrained and soil characteristics as CH 4 sink decreased. The carbon equivalent of emitted greenhouse gases in treatments T1, T2, T3 and T4 in 2009-2010 were respectively 8 880 kg(CO 2).hm -2, 8 372 kg(CO 2).hm -2, 9 600 kg(CO 2).hm -2 and 9 318 kg(CO 2).hm -2; and 13 395 kg(CO 2).hm -2, 12 904 kg(CO 2).hm -2, 13 933 kg(CO 2).hm -2 and 13 189 kg(CO 2).hm -2 in 2010-2011. Differences in greenhouse gas emissions among different treatments were caused by different fertilization and irrigation managements. Straw return or non-return largely led to the differences in greenhouse gas emissions between 2009-2010 and 2010-2011. GWP was relatively low while yield and input-output ratio relatively high in T2. Treatment T2 was therefore considered the optimal management mode for winter-wheat cultivation in the North China Plain.