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We designed a new approach for modeling the nitrous oxide (N2O) derived from nitrogen (N) mineralization associated with loss of soil organic matter (SOM) that meets the current IPCC guidelines (GL...

To identify the soil carbon stock changes from croplands/grasslands to forestlands in Japan, we compared the soil carbon stock of a cropland/grassland with that of an adjacent forestland at 22 different sites. With respect to a 0–30-cm depth basis, the soil carbon stock in the cropland/grassland was the same as that in the forestland; however, it was less than that in the forestland when an equivalent mass approach was used. The ratio of the soil carbon stock in the forestland to that in the cropland/grassland was 1.11 on average, which is comparable with previous mass-corrected paired sampling studies. The ratio was affected by two factors: tree age and current vegetation. Mean annual temperature, mean annual precipitation, phosphate absorption coefficient, litter quantity, and former land use did not affect the ratio. According to a comparison with the results of a paired study for deforestation, the application of the reciprocal of the soil carbon stock ratio of deforestation to the ratio of afforestation was slightly overestimated. Further studies are necessary to establish a general conclusion. Some previous studies, including those involving non-mass-corrected data, are possibly biased, and more studies using the paired sampling method with equivalent mass basis must be conducted to provide the general factor for soil carbon stock change in the future.

International audience; Climate change adaptation, mitigation and food security may be addressed at the same time by enhancing soil organic carbon (SOC) sequestration through environmentally sound land management practices. This is promoted by the “4 per 1000” Initiative, a multi-stakeholder platform aiming at increasing SOC storage through sustainable practices. The scientific and technical committee of the Initiative is working to identify indicators, research priorities and region-specific practices needed for their implementation. The Initiative received its name due to the global importance of soils for climate change, which can be illustrated by a thought experiment showing that an annual growth rate of only 0.4% of the standing global SOC stocks would have the potential to counterbalance the current increase in atmospheric CO2. However, there are numerous barriers to the rise in SOC stocks and while SOC sequestration can contribute to partly offsetting greenhouse gas emissions, its main benefits are related to increased soil quality and climate change adaptation. The Initiative provides a collaborative platform for policy makers, practitioners, scientists and stakeholders to engage in finding solutions. Criticism of the Initiative has been related to the poor definition of its numerical target, which was not understood as an aspirational goal. The objective of this paper is to present the aims of the initiative, to discuss critical issues and to present challenges for its implementation. We identify barriers, risks and trade-offs and advocate for collaboration between multiple parties in order to stimulate innovation and to initiate the transition of agricultural systems toward sustainability.

Response to “The “4p1000” initiative: A new name should be adopted” by Baveye and White (2019)

Rice paddy fields, producing a major staple food to support growing world populations, represent a major source of greenhouse gases (GHGs) from agricultural ecosystems. The GHG emissions, mainly as CH4 and N2O from paddy ecosystems, are highly sensitive to both environmental and management factors. Yet the identification of specific factors, a fundamental step for GHG inventory and mitigation, is often limited by data availability. Here, we compiled 572 and 174 data on CH4 and N2O emissions,respectively, from paddy fields across Japan, which arguably represents the most intensive GHG data set from paddy fields per region. We hypothesized that statistical analyses of the intensive data set allow the identification of key factors and possible mechanisms that have not been fully appreciated in the previous studies. Important environmental factors newly identified for CH4 emission were soil type and precipitation pattern. The soil emitted CH4 the most was Histosols (172% higher) and the least was Andosols (32% lower) compared to the other soil types. Our analysis also revealed that the region of severe summer rainfall (southwestern Japan) tended to have higher CH4 emission. The most critical management-related factor was straw incorporation and its timing had significant impact as previously reported. Specifically, CH4 emission was 242% and 59% higher by pre-puddling and post-harvest incorporation, respectively. The CH4 response to straw incorporation had relatively large uncertainty, which partly resulted from the variation in straw mass and soil type (esp. Andosols). In addition, the soils having inherently low CH4 emission due presumably to more oxidized conditions had significantly higher response to straw incorporation. Organic amendment increased CH4 by 35%, while water management effect was unclear. We also found that N2O accounted only for 5.5% of total global warmingpotential from the paddy fields and was mainly emitted in fallow season (84% of annual emission). The amount of nitrogen fertilizer added, the commonly-used factor to estimate N2O emission (e.g., IPCC guideline) showed no significant relationship with the N2O emission in rice growing season, which may be explained by very low level of fertilizer application in Japanese paddy fields (typically < 100 kg ha-1 y-1) compared to other parts of the world. While some of the findings are unique to specific regions (e.g., Andosols), new findings on the factors and potential mechanisms controlling GHG emissions from rice paddy ecosystems would be useful to develop strategies for regional GHG estimate and for modeling biogeochemical cycle in rice paddy ecosystems.

The aim of this work is to quantify life cycle of nutrient elements for soil and crops, namely nitrogen (N), phosphorus (P), potassium (K), and carbon (C), from feed of livestock to potential of ma...

Methane (CH4) is a greenhouse gas, and paddy fields are one of its main anthropogenic sources. In Japan, country-specific emission factors (EFs) have been applied since 2003 to estimate national-scale CH4 emission from paddy field. However, these EFs did not consider the effects of factors that influence CH4 emission (e.g., amount of organic C inputs, field drainage rate, climate) and can therefore produce estimates with high uncertainty. To improve the reliability of national-scale estimates, we revised the EFs based on simulations by the DeNitrification-DeComposition-Rice (DNDC-Rice) model in a previous study. Here, we estimated total CH4 emission from paddy fields in Japan from 1990 to 2010 using these revised EFs and databases on independent variables that influence emission (organic C application rate, paddy area, proportions of paddy area for each drainage rate class and water management regime). CH4 emission ranged from 323 to 455ktCyr-1 (1.1 to 2.2 times the range of 206 to 285ktCyr-1 calculated using previous EFs). Although our method may have overestimated CH4 emissions, most of the abovementioned differences were presumably caused by underestimation by the previous method due to a lack of emission data from slow-drainage fields, lower organic C inputs than recent levels, neglect of regional climatic differences, and underestimation of the area of continuously flooded paddies. Our estimate (406ktC in 2000) was higher than that by the IPCC Tier 1 method (305ktC in 2000), presumably because regional variations in CH4 emission rates are not accounted for by the Tier 1 method.

To investigate the effect of paddy-upland (PU) rotation system on greenhouse gas emissions, methane (CH4) and nitrous oxide (N2O) emissions were monitored for three years for a PU rotation field (four cultivations (wheat-soybean-rice-rice) over three years) and continuous paddy (CP) field on alluvial soil in western Japan. Soil carbon storage was also calculated using an improved Rothamsted Carbon (RothC) model. The net greenhouse gas balance was finally evaluated as the sum of CO2eq of the CH4, N2O and changes in soil carbon storage. The average CH4 emissions were significantly lower and the average N2O emissions were significantly higher in the PU field than those in the CP field (p &lt, 0.01). On CO2 equivalent basis, CH4 emissions were much higher than N2O emission. In total, the average CO2eq emissions of CH4 plus N2O in the PU field (1.81 Mg CO2 ha&minus, 1 year&minus, 1) were significantly lower than those in the CP field (7.42 Mg CO2 ha&minus, 1) (p &lt, 0.01). The RothC model revealed that the changes in soil carbon storage corresponded to CO2eq emissions of 0.57 and 0.09 Mg CO2 ha&minus, 1 in the both fields, respectively. Consequently, the net greenhouse gas balance in the PU and CP fields were estimated to be 2.38 and 7.51 Mg CO2 ha&minus, 1, respectively, suggesting a 68% reduction in the PU system. In conclusion, PU rotation system can be regarded as one type of the climate-smart soil management.

In the context of their role in global climate change, changes in soil carbon stocks resulting from land use conversions from forest to agricultural lands (cropland and grassland) and subsequent agricultural activities were investigated with data from a total of 46 soil sampling sites across Japan (28 cropland and 18 grassland sites). Collection of soil sample pairs from forest land and adjacent agricultural land converted from forest land allowed derivation of the soil carbon change factor (SCCF; ratio of soil carbon stock in the agricultural land to that in the forest land at the time of soil sampling). Depth-based SCCFs for a fixed depth of 0–30 cm were 23% greater than mass-based SCCFs determined by the equivalent soil mass approach, in which soil carbon stocks in all replicated samples from forest land and agricultural land were calculated for different depths but equal masses of the soil mineral fraction. The overestimation of SCCFs by the depth-based approach was more pronounced in Andosols, particularly in croplands on Andosols, because soil bulk densities in forest lands were much lower than those in croplands on Andosols. The mass-based SCCFs for croplands (upland fields and orchards) and grasslands (pasture land and grazing land) after deforestation were 0.741 ± 0.259 (a 25.9 ± 25.9% decrease in soil carbon stocks after an elapsed time of 2–85 years) and 0.858 ± 0.212 (a 14.2 ± 21.2% decrease after an elapsed time of 26–81 years), respectively. Therefore, conversions from forest land to cropland or grassland resulted in a significant carbon loss from most soils in Japan. Soil carbon stocks in cropland converted from forest land declined as the elapsed time after deforestation increased although the uncertainty was large. Of the environmental variables, soil type (Andosols versus non-Andosols) and tillage frequency during cultivation had little impact on mass-based SCCFs; however, the SCCFs decreased with higher mean annual air temperature at the sites.

International audience; The "4‰" Initiative was launched at the COP21 as part of the Lima-Paris Action Agenda. It aims to improve the organic matter content of soils and promote soil organic carbon (SOC) sequestration to increase soil fertility and thereby contribute to food security, to foster adaptation to climate change and contribute to mitigating climate change. The initiative focuses primarily on agricultural soils, because of their frequent poor soil organic carbon content and degradation and of their crucial role in food provision but also considers forest soils and the preservation of existing SOC stocks. The objectives of the initiative are: (i) to promote research on the knowledge needed for the initiative (mechanisms and potential of organic C sequestration in soils; SOC sequestering management agricultural and forestry practices; adoption and transition to these practices; monitoring SOC stocks) and to (ii) to foster initiatives, by a variety of actors, to better manage SOC in the field via agricultural practices. The gouvernance of the "4‰" Initiative is organised in to three bodies, which will interact closely with each other: the consortium of all members, who elect the president and vice president of the initiative, the forum of partners and the scientific and technical committee (STC). The work of all these bodies is facilitated by the executive secretary. The STC has the mission to support SOC sequestration programs initiated by a wide variety of actors by setting reference criteria for the evaluation of SOC management projects and actions. The committee will give advice on these actions and formulate proposals for the orientations of international scientific research and cooperation programs. The advice given by the STC is founded on the principles and goals of the Initiative and coherent with the Sustainable Development Goals. This presentation will present the on-going work of the STC on the sustainable SOC sequestration indicators. The challenge is to identify easily utilizable indicators relative to SOC storage itself, but also to mitigation of GHG emissions, improved productivity and food security, better adaptation to climate change, but also relative to other impacts of SOC sequestration strategies (on water quality or land tenure for example).

Methane (CH

The "4‰" Initiative was launched at the COP21 as part of the Lima-Paris Action Agenda. It aims to improve the organic matter content of soils and promote soil organic carbon (SOC) sequestration to increase soil fertility and thereby contribute to food security, to foster adaptation to climate change and contribute to mitigating climate change. The initiative focuses primarily on agricultural soils, because of their frequent poor soil organic carbon content and degradation and of their crucial role in food provision but also considers forest soils and the preservation of existing SOC stocks. The objectives of the initiative are: (i) to promote research on the knowledge needed for the initiative (mechanisms and potential of organic C sequestration in soils; SOC sequestering management agricultural and forestry practices; adoption and transition to these practices; monitoring SOC stocks) and to (ii) to foster initiatives, by a variety of actors, to better manage SOC in the field via agricultural practices. The gouvernance of the "4‰" Initiative is organised in to three bodies, which will interact closely with each other: the consortium of all members, who elect the president and vice president of the initiative, the forum of partners and the scientific and technical committee (STC). The work of all these bodies is facilitated by the executive secretary. The STC has the mission to support SOC sequestration programs initiated by a wide variety of actors by setting reference criteria for the evaluation of SOC management projects and actions. The committee will give advice on these actions and formulate proposals for the orientations of international scientific research and cooperation programs. The advice given by the STC is founded on the principles and goals of the Initiative and coherent with the Sustainable Development Goals. This presentation will present the on-going work of the STC on the sustainable SOC sequestration indicators. The challenge is to identify easily utilizable indicators relative to SOC storage itself, but also to mitigation of GHG emissions, improved productivity and food security, better adaptation to climate change, but also relative to other impacts of SOC sequestration strategies (on water quality or land tenure for example).

We determined the historical change in soil organic carbon (SOC) stocks from long-term field trials that represent major soil types and climatic conditions of northern China. Soil carbon and general circulation models were validated using these field trial data sets. We then applied these models to predict future change in SOC stocks to 2100 using two net primary production (NPP) scenarios (i.e., current NPP or 1% year−1 NPP increase). The conversion rate of plant residues to SOC was higher in single-cropping sites than in double-cropping sites. The prediction of future SOC sequestration potential indicated that these soils will be a net source of carbon dioxide (CO2) under no fertilizer inputs. Even when inorganic nutrients were applied, the additional carbon input from increased plant residues could not meet the depletion of SOC in parts of northern China. Manure or straw application could however improve the SOC sequestration potential at all sites. The SOC sequestration potential in northern China was estimated to be −4.3 to 18.2 t C ha−1 by 2100. The effect of projected climate change on the annual rate of SOC change did not differ significantly between climate scenarios. The average annual rate of SOC change under current and increased NPP scenarios (at 850 ppm CO2) was approximately 0.136 t C ha−1 yr−1 in northern China. These findings highlight the need to maintain, and where possible increase, organic carbon inputs into these farming systems which are rapidly becoming inorganic fertilizer intensive.

We have estimated methane (CH4) emission from total rice (Oryza sativa L.) paddies in Japan by means of a process-based biogeochemistry model, DeNitrification-DeComposition(DNDC)-Rice, combined with a geographic information system (GIS) database of climate, soil and farming practices. In the GIS database, 2 million ha of rice paddies were divided into 17,408 units according to 136 climate areas, 16 soil types, four classes of drainage rate and two classes of groundwater level, to simulate CH4 flux from each of the units applying the DNDC-Rice model. As a result, the national-scale CH4 emission in 1990 was estimated to be 216 Gg carbon (C), 13% lower than a previous inventory estimated by the Tier 2 method. By our Tier 3 approach, a relatively higher CH4 flux was estimated from eastern regions than from western regions of Japan, presumably due to the differences in climate and water management. Sensitivity analysis and uncertainty assessment indicated that it is important to account for the heterog...

Summary The 14C contents and the carbon (C) pool sizes for Rothamsted Carbon (RothC) model pools and soil fractions determined by physical separation and subsequent chemical oxidation were directly compared for an agricultural topsoil (Dystric Cambisol) from a long-term experimental field in central Japan. The RothC model was run from 1975 to 2009 and the C concentration and Δ14C value of each pool and for the bulk soil were compared with the physical fractions that have been, according to literature, suggested as corresponding with model pools. When compared with the default estimate of the inert organic matter (IOM) pool size derived from an exponential dependency on total organic carbon (TOC), direct estimation of IOM pool size determined from the C remaining after chemical oxidation of the silt plus clay (

To relate short-term nutrient balances with long-term changes in soil fertility, we compared soil available-nutrient stores with fertilizer application, crop productivity, and nutrient balances. Stores of nitrogen (N: quantity of available N), phosphorus (P: quantity of Truog-P), and potassium (K: quantity of exchangeable K) in the topsoil were calculated five times from 1979 to 2003. In each survey, nutrient inputs by fertilizer, manure, and soil amendment and output by crop removal were calculated. The arithmetic average was calculated for seven crop groups [(paddy rice, Oryza sativa L.), upland crop (wheat, Poaceae triticum L., etc.), vegetables (radish, Raphanus sativus L. etc.), orchards (orange, Malus pumila Mill. etc.), tea (Camelia sinensis L.), forage (Dent corn, Zea mays L. etc.), fodder (timothy, Pheleum pratense L., etc.)] on 16 groups of soils. In spite of large changes in the N balance and in manure N input, available N was relatively constant during the five surveys both within and...

At the Takayama deciduous broadleaved forest Asiaflux site in Japan, the ecosystem carbon dynamics have been studied for more than two decades. In 2005, we installed non-dispersive infrared CO2 sensors in the soil below the site’s flux tower to systematically study vertical soil–air CO2 dynamics and explain the behavior of soil surface CO2 efflux. Soil–air CO2 concentrations measured from June 2005 through May 2006 showed sinusoidal variation, with maxima in July and minima in winter, similar to the soil CO2 effluxes measured simultaneously using open-flow chambers. Soil–air CO2 concentrations increased with soil depth from 5 to 50 cm: from 2,000 to 8,000 ppm in the summer and from 2,000 to 3,000 ppm in the winter under snow. Summer soil–air CO2 concentrations were positively correlated with soil moisture on daily and weekly scales, indicating that the Oi, Oe, and A horizons, where decomposition is accelerated by high-moisture conditions, contributed substantially to CO2 emissions. This result is consistent with the short residence time (about 2 h) of CO2 in the soil and larger emissions in shallow soil layers based on our diffusion model. We revealed for the first time that soil–air CO2 concentrations in winter were correlated with both snow depth and wind speed. CO2 transfer through the snow was hundreds of times the gas diffusion rates in the soil. Our estimate of the CO2 efflux during the snow-cover season was larger than previous estimates at TKY, and confirmed the important contribution of the snow-cover season to the site’s carbon dynamics.

We compared predictions of the modified Rothamsted Carbon Model (RothC) for paddy soils (RothC-26.3_p), with decomposition rate constants set at 0.2 and 0.6 times the values in the original RothC-26.3 for submerged and drained periods, respectively, with the results of five long-term field studies in southern China. These field studies included two paddy-upland rotation sites (Chongqing and Wuchang) and three double rice cropping sites (Wangcheng, Nanchang, and Jinxian). Several treatments (no fertilizer, inorganic fertilizer, and inorganic fertilizer with organic amendments such as straw, green manure, and farmyard manure) were tested at each site. RothC-26.3_p satisfactorily simulated the observed changes in soil organic carbon (SOC) at all paddy-upland rotation sites and in all plots without organic matter application at the double rice cropping sites, but overestimated SOC in plots with organic matter application at double rice cropping sites. We conclude that RothC-26.3_p is suitable for use in China...

Temperature sensitivity of soil organic matter (SOM) decomposition may have a significant impact on global warming. Enzyme-kinetic hypothesis suggests that decomposition of low-quality substrate (recalcitrant molecular structure) requires higher activation energy and thus has greater temperature sensitivity than that of high-quality, labile substrate. Supporting evidence, however, relies largely on indirect indices of substrate quality. Furthermore, the enzyme-substrate reactions that drive decomposition may be regulated by microbial physiology and/or constrained by protective effects of soil mineral matrix. We thus tested the kinetic hypothesis by directly assessing the carbon molecular structure of low-density fraction (LF) which represents readily accessible, mineral-free SOM pool. Using five mineral soil samples of contrasting SOM concentrations, we conducted 30-days incubations (15, 25, and 35 °C) to measure microbial respiration and quantified easily soluble C as well as microbial biomass C pools before and after the incubations. Carbon structure of LFs (

Research networks provide a framework for review, synthesis and systematic testing of theories by multiple scientists across international borders critical for addressing global-scale issues. In 2012, a GHG research network referred to as MAGGnet (Managing Agricultural Greenhouse Gases Network) was established within the Croplands Research Group of the Global Research Alliance on Agricultural Greenhouse Gases (GRA). With involvement from 46 alliance member countries, MAGGnet seeks to provide a platform for the inventory and analysis of agricultural GHG mitigation research throughout the world. To date, metadata from 315 experimental studies in 20 countries have been compiled using a standardized spreadsheet. Most studies were completed (74%) and conducted within a 1–3-year duration (68%). Soil carbon and nitrous oxide emissions were measured in over 80% of the studies. Among plant variables, grain yield was assessed across studies most frequently (56%), followed by stover (35%) and root (9%) biomass. MAGGnet has contributed to modeling efforts and has spurred other research groups in the GRA to collect experimental site metadata using an adapted spreadsheet. With continued growth and investment, MAGGnet will leverage limited-resource investments by any one country to produce an inclusive, globally shared meta-database focused on the science of GHG mitigation. Inst. de Clima y Agua Fil: Liebig, M.A. United States Department of Agriculture. Agricultural Research Service; Estados Unidos Fil: Posse Beaulieu, Gabriela. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Clima y Agua; Argentina Fil: Lewczuk, Nuria. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Clima y Agua; Argentina Fil: Franzluebbers, A.J. United States Department of Agriculture. Agricultural Research Service; Estados Unidos. NC State University. Campus; Estados Unidos Fil: Alvarez, Carolina. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Manfredi; Argentina Fil: Chiesa, Tomás Della. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina Fil: Piñeiro, Gervasio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina Fil: Yahdjian, María Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina Fil: Grace, P. Queensland University of Technology; Australia Fil: Cabral, Osvaldo Machado Rodrigues. Embrapa Environment; Brasil Fil: Martin-Neto, Ladislau. Embrapa. Departamento de Administração do Parque Estação Biológica; Brasil Fil: Rodrigues, Renato de Aragao Ribeiro. Embrapa Solos; Brasil Fil: Angers, D. Agriculture and Agri-Food Canada; Canadá Fil: Hao, X. Agriculture and Agri-Food Canada, Lethbridge; Canadá Fil: Oelbermann, M. University of Waterloo; Canadá Fil: Tenuta, M. University of Manitoba. Department of Soil Science; Canadá Fil: Munkholm, L.J. Aarhus University. Department. of Agroecology; Dinamarca Fil: Regina, K. Natural Resources Institute; Finlandia Fil: Cellier, Pierre. Institut National de la Recherche Agronomique; Francia Fil: Ehrhardt, Fiona. Institut National de la Recherche Agronomique; Francia Fil: Richard, G. Institut National de la Recherche Agronomique; Francia Fil: Dechow, R. Thünen Institute of Climate Smart Agriculture; Alemania Fil: Agus, F. Indonesian Soil Research Institute; Indonesia Fil: Widiarta, N. Indonesian Center for Food Crop Research and Development; Indonesia Fil: Spink, J. Oak Park Crops Research Centre; Irlanda Fil: Berti, Antonio. Università di Padova. Dipartimento di Agronomia Animali Alimenti Risorse Naturali e Ambiente; Italia Fil: Grignani, Carlo. Università degli Studi di Torino. Dipartimento di Scienze Agrarie, Forestali e Alimentari; Italia Fil: Mazzoncini, Marco. Università di Pisa. Dipartimento di Agronomia e Gestione dell'Agroecosistema; Italia Fil: Orsini, Roberto. Universita Politecnica delle Marche. Dipartimento di Scienze Agrarie Alimentari e Ambientali; Italia Fil: Roggero, Pier Paolo. Universita di Sassari. Dipartimento di Agraria. Nucleo di Ricerca sulla Desertificazione; Italia Fil: Seddaiu, Giovanna. Universita di Sassari. Dipartimento di Agraria. Nucleo di Ricerca sulla Desertificazione; Italia Fil: Tei, Francesco. Università di Perugia. Dipartimento di Scienze Agrarie, Alimentari ed Ambientali; Italia Fil: Ventrella, Domenico. Research Unit for Cropping Systems in Dry Environments; Italia Fil: Vitali, Giuliano. Universita di Bologna. Dipartimento di Scienze Agrarie, Alma Mater Studiorum; Italia Fil: Kishimoto-Mo, A. National Institute for Agro-Environmental Sciences; Japón Fil: Shirato, Y. National Institute for Agro-Environmental Sciences; Japón Fil: Sudo, S. National Institute for Agro-Environmental Sciences; Japón Fil: Shin, J. National Academy of Agricultural Science; Corea del Sur Fil: Schipper, L. University of Waikato. Environmental Research Institute; Nueva Zelanda Fil: Leifeld, J. Agroscope; Suiza Fil: Spadavecchia, L. Department for Environment, Food & Rural Affairs; Reino Unido Fil: Yeluripati, J. The James Hutton Institute; Escosia Fil: Del Grosso, Stephen J. United States Department of Agriculture. Agricultural Research Service; Estados Unidos Fil: Rice, Charles W. Kansas State University; Estados Unidos Fil: Sawchik, Jorge. Instituto Nacional de Investigación Agropecuaria; Uruguay

Change in temperature sensitivity of soil organic carbon (SOC) decomposition with change in soil qualities (i.e. decomposability or lability) is one of the most important issues to be evaluated for projection of future CO 2 emissions from soils. We inversely estimated the temperature sensitivity of SOC decomposition rate by applying a hybrid of the Metropolis-Hasting algorithm and the particle filter method to the extended Rothamsted carbon model (RothC), together with long-term (9 years) experimental data on SOC obtained at five sites in Japanese upland soils. Contrary to the prediction of the Arrhenius kinetics theory, we found no significant differences in temperature sensitivity among soils with different qualities (represented as soil compartments in the RothC model). We also confirmed that there was a positive correlation between the relative temperature sensitivity of the humus compartment and future total CO 2 emissions. The RothC model with default parameterization tended to overestimate future total CO 2 emissions relative to the calibrated model, and the degree of overestimation was larger than that of underestimation.

Using data from a longitudinal survey (the Basic Soil Environment Monitoring Project, Stationary Monitoring, 1979–1998, launched by the Ministry of Agriculture, Forestry and Fisheries of Japan), it was found that livestock possession, soil type, utilization form of paddy fields and full-/part-time status of farmers were important factors controlling application rates of organic amendments (OA) in Japanese paddy fields. When data points were categorized in terms of these four factors, application rate of livestock waste compost (LWC) on the basis of fresh weight (FW) varied remarkably. Application rates of LWC decreased during the survey period, whereas rice straw residue (RSR) application rates increased. The smallest LWC application rate (average 0.3 ± 0.2 Mg FW ha−1 for the period between 1994 and 1998) was found among rice (Oryza sativa L.) single-cropping, poorly drained lowland paddy soils (PDLPS) including Histosols, with full-time farmers possessing no livestock. Even among rice single-cropping, th...

We estimated the application of cattle, swine, and poultry manure and of rice straw and rice straw compost for seven crop groups (paddy rice, upland crops, vegetables, orchards, tea, forage, and fodder) from a bottom-up analysis of government questionnaire data. Vegetable crops consumed the most manure and received the largest amount of swine and poultry manure and of rice straw compost, and the second-highest amount of cattle manure. Paddy rice received the least manure, and depended mainly on organic matter from non-composted rice straw. Fodder (timothy (Phleum pratense. L.), etc.) and forage (dent corn (Zea mays L.), etc.) crops used for cattle husbandry consumed the most cattle manure; however, fodder crops received only one-quarter of the cattle manure received by forage crops. We hypothesized phosphorus (P) is not lost during composting, then estimated the amount of raw materials for livestock manure inversely from applied livestock manure P and carbon (C):nitrogen (N):potassium (K):P ratio of kinds...

Soil C sequestration in croplands is deemed to be one of the most promising greenhouse gas mitigation options for Japan's agriculture. In this context, changes in soil C stocks in northern Japan's arable farming area over the period of 1971–2010, specifically in the region's typical Andosol (volcanic ash-derived) and non-Andosol soils, were simulated using soil-type-specific versions of the Rothamsted carbon model (RothC). The models were then used to predict the effects, over the period of 2011–2050, of three potential management scenarios: (i) baseline : maintenance of present crop residue returns and green manure crops, as well as composted cattle manure C inputs (24–34 Mg ha −1 yr −1 applied on 3–55% of arable land according to crop), (ii) cattle manure : all arable fields receive 20 Mg ha −1 yr −1 of composted cattle manure, increased C inputs from crop residues and present C inputs from green manure are assumed, and (iii) minimum input : all above-ground crop residues removed, no green manure crop, no cattle manure applied. Above- and below-ground residue biomass C inputs contributed by 8 major crops, and oats employed as a green manure crop, were drawn from yield statistics recorded at the township level and crop-specific allometric relationships (e.g. ratio of above-ground residue biomass to harvested biomass on a dry weight basis). Estimated crop net primary production (NPP) ranged from 1.60 Mg C ha −1 yr −1 for adzuki bean to 8.75 Mg C ha −1 yr −1 for silage corn. For the whole region (143 × 10 3 ha), overall NPP was estimated at 952 ± 60 Gg C yr −1 (6.66 ± 0.42 Mg C ha −1 yr −1 ). Plant C inputs to the soil also varied widely amongst the crops, ranging from 0.50 Mg C ha −1 yr −1 for potato to 3.26 Mg C ha −1 yr −1 for winter wheat. Annual plant C inputs to the soil were estimated at 360 ± 45 Gg C yr −1 (2.52 ± 0.32 Mg C ha −1 yr −1 ), representing 38% of the cropland NPP. The RothC simulations suggest that the region's soil C stock (0–30 cm horizon), across all soils, has decreased from 13.96 Tg C (107.5 Mg C ha −1 yr −1 ) in 1970 to 12.46 Tg C (96.0 Mg C ha −1 yr −1 ) in 2010. For the baseline, cattle manure and minimum input scenarios, soil C stocks of 12.13, 13.27 and 9.82 Tg C, respectively, were projected for 2050. Over the period of 2011–2050, compared to the baseline scenario, soil C was sequestered (+0.219 Mg C ha −1 yr −1 ) by enhanced cattle manure application, but was lost (−0.445 Mg C ha −1 yr −1 ) under the minimum input scenario. The effect of variations of input data (monthly mean temperature, monthly precipitation, plant C inputs and cattle manure C inputs) on the uncertainty of model outputs for each scenario was assessed using a Monte Carlo approach. Taking into account the uncertainty (standard deviation as % of the mean) for the model's outputs for 2050 (5.1–6.1%), it is clear that the minimum input scenario would lead to a rapid decrease in soil C stocks for arable farmlands in northern Japan.

Strong correlations of soil total organic carbon (OC) with iron and aluminum phases reported frequently make it important to quantify these organic matter (OM) associations, but selective extractants sometimes contain OC. Soil nitrogen is often predominantly organic and might serve as a proxy for OM. We therefore investigated nitrogen associations with Fe and Al using several selective extractants that use reductive, complexation, and alkaline approaches. Total dissolved nitrogen (TDN) correlated strongly with extracted Fe and Al across seventeen samples, including highly- and weakly-weathered soils, iron-rich ultrabasic soils, podzolic, and volcanic soils. Typically a quarter to a third of total soil nitrogen was dissolved by the various extractions, though higher fractions (up to 60%) were found in spodic-horizon and volcanic surface-horizon samples. Similar proportions were found for OC, using three OC-free extractants, indicating that TDN provides a useful surrogate for assessing OM partitioning via extractants that contain OC. Use of TDN:metal ratios in extractant solutions allows estimation of extracted OM that could have been sorptively associated with metal oxide/hydroxides and poorly-crystalline aluminosilicates. These ratios were often high in extractions targeted at these adsorbents, and imply that usually most of the extracted TDN consists instead of organo–metal complexes. The dynamics of these complexes may have stronger control on accumulation/remobilization of soil OM than those of metal oxyhydroxides and poorly-crystalline aluminosilicates.

The conventionally-modified RothC model for Andosols required pyrophosphate-extractable aluminum (Alp) for changing humus decomposition rate of the original RothC model. However, any Japanese soil database, which were derived from national soil survey projects, did not have the Alp dataset, and thus the conventionally-modified RothC model required Alp prediction from soil organic carbon (SOC) content. From this reason, there is a risk of Alp prediction error in the run-up to predict the SOC turnover. Objectives of this study were (1) to explore the alternative soil property for re-modifying the conventionally-modified RothC model and (2) to validate the re-modified model against long-term experimental data sets of Japanese Andosols. Phosphate adsorption coefficient (PAC), which is an indicator of the content of amorphous aluminum (Al) and iron (Fe) compounds, was tested to replace Alp using three Andosols database. A stability factor, H(f), was defined as the factor needed to divide the decomposition rate...

We estimated the carbon (C) sequestration potential of organic matter application in Japanese arable soils at a country scale by applying the Rothamsted carbon (RothC) model at a 1-km resolution. After establishing the baseline soil organic carbon (SOC) content for 1990, a 25-year simulation was run for four management scenarios: A (minimum organic matter application), B (farmyard manure application), C (double cropping for paddy fields) and D (both B and C). The total SOC decreased during the simulation in all four scenarios because the C input in all four scenarios was lower than that required to maintain the baseline 1990 SOC level. Scenario A resulted in the greatest depletion, reflecting the effects of increased organic matter application in the other scenarios. The 25-year difference in SOC accumulation between scenario A and scenarios B, C and D was 32.3, 11.1 and 43.4 Mt C, respectively. The annual SOC accumulation per unit area was similar to a previous estimate, and the 25-year averages...

Starting in 2005, we examined differences in vegetation for three consecutive years across an airport fence that separated heavily grazed areas from areas in which grazing had been excluded for 24 years in Mandalgobi, Mongolia. We performed repeated-measures analysis separately on two community types (dominated by Allium polyrrhizum and Achnatherum splendens, respectively) to compare the effects of fencing and year on the cover of different plant functional types. There was a significant fence x year interaction for grass cover in the Allium type (but not the Achnatherum type), due to greater cover of grasses inside the fence only when rainfall was sufficient during the growing season. The effect of grazing exclusion on perennial forb cover was confounded by a significant fence x year interaction in both types. In 2007, perennial forbs were found outside the fence, but had almost disappeared inside the fence, resulting in this interaction. Annual forbs only had much greater cover values inside the fence than outside in 2006, also resulting in a significant fence x year interaction in both community types. This study thus suggests that the high rainfall variability in arid and semi-arid rangelands may modify the effects of long-term exclosure on vegetation.

Soil CO2 concentrations to a depth of 50 cm depth were monitored with Vaisala CO2 probes from June 2004 to May 2005 in conventionally plowed and no-tillage agricultural plots and found to be generally higher in the former than the latter. Soil CO2 concentrations were also higher in summer and lower in winter, but were modulated by harvesting and the application of crop residues. Analysis of diurnal variations in soil CO2 concentrations, soil CO2 effluxes, and soil temperatures revealed distinct differences between plots. The relative amplitudes of the variation in CO2 concentrations peaked at a soil depth of 5 cm. Soil CO2 concentrations were higher when there was higher soil water content after precipitation, while soil CO2 effluxes were lower under the same circumstances. These two results relate to the lower diffusivity at higher soil water content, which restricts CO2 efflux, leading to higher soil CO2 concentrations. Calculations reveal that in the shallower soil layer (0-5 cm), CO2 production was greater in no-tillage plots, whereas in the deeper layer (15-25 cm), it was greater in conventional plots.

Effect of land use change from paddy rice cultivation to upland crop cultivation on soil carbon budget (SCB) was studied by comparing three types of cropping system (single cropping of paddy rice (PR), single cropping of upland rice (UR) and double cropping of soybean and wheat (SW)) in an experimental field having the same history as consecutively cultivated paddy rice fields. The carbon dioxide (CO_2) and methane (CH_4) fluxes from the fields were measured continuously over 2.5 years with an automated flux monitoring system. Atmospheric CO_2 was significantly absorbed during the growth periods of different crops, including all the summer crops and winter wheat. The amounts of absorbed CO_2 during the summer crop growth period were highest in the PR plots and lowest in the UR plots. On the other hand, CO_2 emission was observed during the fallow period. In addition, a significantly high peak and the subsequent gradual decrease in CO_2 emission were observed after plowing the fields in autumn. Significant CH_4 emission was found in only the PR plots during the submerged period. With consideration of gas flux data and the amount of carbon supplied and removed by agricultural management practices such as straw incorporation and crop harvest, the SCB in the croplands was estimated. The soil carbon budgets of the PR plots were positive (79-137 g C m^ y), which indicates the accumulation of carbon in the soil. On the other hand, those of the UR and SW plots were negative (−343 to −275 g C m y and −361 to −256 g C m season, respectively), which indicates significant carbon loss from the soil. The contribution of CH_4 emission to SCB was small compared with that of CO_2 dynamics. Significant differences in the carbon content of the top soil between the plots were also found after the experiment, consistent with the above SCB result. The results indicate that land use change from paddy rice cultivation to upland crop cultivation causes significant loss of carbon from cropland soil.

We focused on land units as landscape characteristics and selected seven typical land units on a land catena comprising two areas of southern Mongolia. Hierarchical analysis was used to test the hypothesis that a land unit's edaphic factors could explain the differences in vegetation responses to grazing. We established the survey sites at increasing distances from a livestock camp or water point within each land unit, then analysed patterns of change in floristic and functional compositions, vegetation volume and soil properties within each land unit to reveal differences in vegetation responses to grazing. We also examined the variations in floristic and functional compositions across land units to identify the edaphic factors that may underlie these differences. Changes in vegetation and soil properties at increasing distances from a camp or water point within each land unit were into three different patterns. Ordination tech- niques consistently indicated that land unit groups categorised using edaphic factors corre- sponded to those categorised using response patterns. Our study revealed that edaphic factors were responsible for the observed landscape- scale differences in vegetation responses to grazing in the study areas. In addition, the mechanisms underlying vegetation responses to grazing may have been primarily determined by edaphic factors.

Methane (CH4) is a greenhouse gas, and paddy fields are one of its main anthropogenic emission sources. To mitigate this emission based on effective management measures, CH4 emission from paddy fields must be quantified at a national scale. In Japan, country-specific emission factors have been applied since 2003 to estimate national CH4 emission from paddy fields. However, this method cannot account for the effects of weather conditions and temporal variability of nitrogen fertilizer and organic matter application rates; thus, the estimated emission is highly uncertain. To improve the accuracy of national-scale estimates, we calculated country-specific emission factors using the DeNitrification-DeComposition-Rice (DNDC-Rice) model. First, we calculated CH4 emission from 1981 to 2010 using 986 datasets that included soil properties, meteorological data, and field management data. Using the simulated site-specific emission, we calculated annual mean emission for each of Japan's seven administrative regions, two water management regimes (continuous flooding and conventional mid-season drainage), and three soil drainage rates (slow, moderate, and fast). The mean emission was positively correlated with organic carbon input to the field, and we developed linear regressions for the relationships among the regions, water management regimes, and drainage rates. The regression results were within the range of published observation values for site-specific relationships between CH4 emission and organic carbon input rates. This suggests that the regressions provide a simplified method for estimating CH4 emission from Japanese paddy fields, though some modifications can further improve the estimation accuracy.

Using various plant materials, we identified two conceptual pools of plant litter, decomposable plant material (DPM) and resistant plant material (RPM), in the Rothamsted Carbon Model (RothC) by comparing the default proportions of DPM and RPM in the RothC and proportions in plant material fractions as determined by two-step acid hydrolysis with H 2 SO 4 . We collected 37 plant samples from 15 species at six sites on arable land, grassland, or forest in Japan. Carbon in the plant materials was divided into three pools by acid hydrolysis: (a) Labile Pool I (LP I), obtained by hydrolysis with 5 N H 2 SO 4 at 105 °C for 30 min; (b) Labile Pool II (LP II), obtained by hydrolysis with 26 N H 2 SO 4 at room temperature overnight, and then with 2 N H 2 SO 4 at 105 °C for 3 h; and (c) Recalcitrant Pool (RP), the unhydrolyzed residue. The average proportion of LP I in crops and grasses was 59%, which was the same as the proportion of DPM defined in the RothC as the default value for crops and grasses. The remaining 41% (23% LP II+18% RP) was consequently the same as the RPM proportion defined in the RothC. Similarly, the average proportion of LP I in all tree leaves (19%) was very close to the proportion of DPM in the RothC (20%) for trees. These results indicate that DPM in the RothC can be identified as LP I from the acid hydrolysis analysis and RPM as LP II+RP. We conclude that, at least theoretically, the use of an independent DPM:RPM ratio, as determined by acid hydrolysis analysis for each plant material, should enable more reliable modeling of SOM dynamics than the use of default DPM:RPM values provided by the model, even though the practical advantages of this method require further evaluation.

We applied the Rothamsted Carbon Model (RothC), which was developed for simulating the soil organic carbon (SOC) turnover in non-waterlogged soils, for long-term experiments (16–22 years) on Japanese paddy soils and modified it to accurately simulate the changes in the content of SOC with time in paddy soils. The RothC underestimated the SOC content in all the nine plots at five sites: Gley Soils in Akita and Shimane, Gray Lowland Soils in Toyama and Mie, and Yellow Soil in Oita prefecture. This may be mainly due to the slow decomposition rate of organic matter during the rice-growing season, when submerged soils are waterlogged and subjected to anaerobic conditions. On the other hand, the decomposition of organic matter might be inhibited, not only during the submergence period but also throughout the year in paddy soils because of the difference in the composition of microorganisms between upland and paddy soils. Taking these possibilities of differences in the decomposition rate between upland soils an...

The suitability of the DeNitrification-DeComposition (DNDC) model for simulating long-term changes in the content of soil organic carbon (SOC) was validated using 5 sites for long-term experiments related to Japanese paddy soils. Since the model could not simulate crop growth adequately, several crop growth parameters provided by the model as default were changed to adjust crop growth to the observation. Overall, the changes in the content of SOC with time simulated by DNDC using adjusted crop parameters, agreed well with the observation in 9 plots from 5 experimental sites during the 16 to 22-year period of the experiment. The good performance of the decomposition sub-model in the DNDC was verified in the long-term SOC decomposition in paddy soils as well as in upland soils reported in previous studies. However, the simulated SOC did not agree well with the observation in some plots, especially in soils with a very low SOC content, suggesting that care should be exercised when applying the model to soils...

In a field experiment we evaluated the effects of exclosure and sand-fixing measures on land restoration of shifting sand dunes in a semi-arid, sandy grassland located in Northern China. We fenced an area of about 2.1 ha, enclosing 2 shifting sand dunes—one large and the other small. In 1996, on each dune we applied 2 sand-fixing measures developed in China—burying wheat straw in a checkered pattern (Sc) and planting seedlings of a sand-fixing shrub, Artemisia halodendron (Ar). Changes in the topographical features and soil properties were then monitored for 6 years. The effectiveness of the sand-fixing measures was assessed by monitoring the topographical features and soil properties. Sand dune fixation took 1 year, and a biological soil crust with high contents of soil organic carbon and fine particles (clay+silt) was formed within 3 years. These results are consistent with those reported in previous studies, confirming that such crusts reduce wind erodibility. The effectiveness of exclosure alone, with...

An experiment was implemented in 1997 in the Horqin Sandy Land of Inner Mongolia, China to evaluate the effects of different measures of stabilizing sand dune on vegetation restoration. The measures included (1) building corn straw fencing, (2) placing wheat straw checkerboard, and (3) planting Artemisia halodendron on the dunes. The preliminary results from the first 2 years (1998 and 1999) demonstrate that all the three measures could result in significant increases of plant species diversity, vegetation cover, above-ground biomass and below-ground biomass on the moving sand dunes relative to the naturally restored plot (without taking any measures). However, both placing wheat straw checkerboard and planting Artemisia halodendron performed best and thus are considered to be the most promising techniques for the restoration of vegetation on desertified sandy lands in this area.

We studied the changes in soil properties after afforestation on desertification-affected sandy soils to estimate how much time would be required for soils to recover enough for use in sustainable food production. We surveyed soils near and within 3-, 9-, and 19year- old plantations of poplar (Poplus simonii) in the central part of Naiman County, eastern Inner Mongolia, China. Changes in the soil properties following afforestation included an accumulation of fine particles (clay + silt) and soil organic carbon (SOC) in the surface horizons. The contents of fine particles and SOC increased slowly in the first 9-year period and then rapidly between 10 and 19 years, being higher at concave than convex sites. Soil parameters such as available moisture level, amounts of available N and available P, and CEC that control soil fertility showed a similar trend to that of the contents of fine particles and SOC. The contents of fine particles and SOC were higher at the windward edge than in the center of th...

In the Horqin Sandy Land of eastern Inner Mongolia in northern China, wind erosion in farmland is very common in a period from thawing of frozen surface soil in mid-March to sowing of crops in the end of April, largely because of dry and windy weather. However, little is known about the magnitude of wind erosion and associated nutrient losses due to erosion and the addition of nutrients by airborne dust deposition to farmlands during this period. A field experiment was conducted in an Entisol with sand origin under corn ( Zea mays L.) production to investigate daily changes in wind speed and wind erosion intensity (as measured by soil transport rate) over a period from 20 March to 30 April 2001. We also measured daily rates of airborne dust deposition during the spring seasons with the high frequency of dust storm occurrence. The rates of soil transport by wind varied greatly from 13.2 to 1254.1 kg ha −1 per day, averaging 232.1 kg ha −1 per day, largely attributable to great variation between days in wind speed within the study period. The potential losses of nutrients through wind erosion were 0.26–24.95 kg ha −1 per day (averaging 4.62 kg ha −1 per day) in organic matter, 0.02–1.64 kg ha −1 per day (averaging 0.31 kg ha −1 per day) in nitrogen and 0.01–0.7 kg ha −1 per day (averaging 0.13 kg ha −1 per day) in phosphorus. The mean rates of airborne dust deposition ranged from 4.0 to 48.9 kg ha −1 per day, averaging 19.9 kg ha −1 per day, during the spring seasons. The potential addition of organic matter, nitrogen and phosphorus by dust input to the experimental field was, on average, 0.54, 0.04 and 0.02 kg ha −1 per day, respectively. Although the addition was a fraction of the losses due to erosion, nevertheless, dust input in the spring seasons is one of the major suppliers of soil nutrition. The fact that the addition of nutrients by dust is about 1/10 of the losses of soil nutrients through wind erosion suggests that developing and adopting more effective management practices to reduce soil erosion losses and to improve soil fertility are crucial to achieve a sustainable agricultural system in a fragile, semiarid sandy land environment.

We modified the Rothamsted carbon model (RothC) to adopt it to Andosols. We changed the decomposition rate constant of the humus (HUM) pool because the presence of Al-humus complexes in Andosols gives HUM strong stability. In addition, the inert organic matter (IOM) pool was set at zero, because the soil did not contain carbon when it was formed from fresh volcanic ash. H(f) was defined as the factor required to divide the decomposition rate constant of the HUM pool so that the modelled soil organic carbon (SOC) level matched the measured level. H(f) was calculated for 32 Japanese Andosols, and the relationships between H(f) and soil properties such as contents of acid-oxalate-extractable Al, Fe, and Si (Mo, Feo, and Sio) or pyrophosphate-extractable Al (Alp) were analysed. The equation H(f) =1.20 + 2,50Alp(% ), (r 2 = 0.518) was selected to divide the decomposition rate constant of HUM. The modified model was tested for four long-term experimental data sets on Andosols under various climatic con...

We evaluated the suitability of the Rothamsted Carbon (RothC) model for long-term experiments on Japanese non-volcanic upland soils using 6 long-term experimental data sets: 2 Brown Lowland Soils, 2 Yellow Soils, 1 Gray Lowland Soil, and 1 Brown Forest Soil. The predicted changes in the content of soil carbon with time were very close to the observed values in almost all the treatments at all the 6 sites. These 6 sites were distributed from North to South across Japan and included a variety of climatic conditions, soil textures, and land management practices. We therefore concluded that the RothC model adequately simulated changes in the soil carbon content with time in Japanese non-volcanic upland soils.

To assess the pedoecological effects of a 23-year old poplar (Populus simonii Carr.) forest on soil amelioration and vegetation restoration via soil erosion reduction and atmospheric dust retention in a desertified sandy land ecosystem, daily dynamics of wind speed, sand transport and dust deposition rates were monitored over an erosive period from April through June in 2001, using fixed observation sites located at different positions within and around the forest. Soil and vegetation characteristics at these sites were also measured. The observation sites were placed at distances of 15H (as control), 6H and 3H (H is mean tree height) from the forest edge of the windward side (abbreviated CK, 6H-W and 3H-W respectively), forest center (FC), and at distances of 0H, 6H and 8H from the forest edge of the leeward side (FE-L, 6H-L and 8H-L respectively). Daily mean wind speed was significantly lower in different observation sites than CK, with FC having the greatest reduction of wind speed and 6H-W the least reduction. Daily transport rate of sand by wind was also significantly lower in different observation sites than CK, with FE-L having the greatest reduction of wind erosion and 6H-W the least reduction. The fact that the poplar forest will lose its functions against wind at a distance of about 12-fold tree height from the forest edge of the leeward side suggests that the effective wind-preventing range of the poplar forest is about 150 m. There was marked spatial and seasonal distribution of dust-fall rate. Over space, the rate of dust-fall was much greater within the forest than outside the forest. Over time, the daily dust deposition rate was greatest in April, followed in decreasing order by May, June, July, September and August, closely linked to the seasonal distribution pattern of dust storm. Significant positive changes in soil and vegetation parameters of the different observation sites during the 23 years that the poplar forest was established suggest the perceptible pedoecological effects of the poplar forest on soil development and restorative succession of plant community within its immediate vicinity through windbreak, soil erosion reduction and atmospheric dust retention. Understanding these pedoecological effects may aid in the design of protective forest systems in arid and semi-arid areas.

We studied chemical kinetics of weathering in the humus horizons of young Andisols from northeastern Japan. Since there is no idealized chronosequence of Andisols, we selected eight pedons that have many similarities in the properties of parent material, soil moisture regime, vegetation, drainage, etc., but show significant differences in soil age and soil temperature. We introduced “soil age normalized to 10°C,” which was defined as the number of years a soil has been subjected to pedogenesis under mean monthly soil temperature (MMST) of 10°C throughout the year. For this calculation, temperature dependency coefficient (Q10) of Al release from volcanic glass was determined to be 1.5 by the laboratory dissolution experiment using separated glass samples. Mean monthly air temperature (MMAT) plus 1°C was employed as MMST based both on the comparison between MMST and MMAT and the determination of diurnal variations of soil temperature. Of the various elements contained in volcanic ash, Al was found to be most reliable for evaluating chemical weathering of the bulk soils, and released Al was determined by the acid oxalate method. The correlation between the soil age normalized to 10°C and acid oxalate extractable Al (Alo) showed that the chemical weathering is expressed as zero-order kinetics.