Spatial Characteristics of Soil Organic Carbon Storage in China＇s Croplands

The soil organic carbon （SOC） pool is the largest component of terrestrial carbon pools. With the construction of a geographically referenced database taken from the second national general soil survey materials and based on 1546 typical cropland soil profiles, the paddy field and dryland SOC storage among six regions of China were systematically quantified to characterize the spatial pattern of cropland SOC storage in China and to examine the relationship between mean annual temperature, precipitation, soil texture features and SOC content. In all regions, paddy soils had higher SOC storage than dryland soils, and cropland SOC content was the highest in Southwest China. Climate controlled the spatial distribution of SOC in both paddy and dryland soils, with SOC storage increasing with increasing precipitation and decreasing with increasing temperature.     

Land Use and Soil Organic Carbon in China’s Village Landscapes

Village landscapes, which integrate small-scale agriculture with housing, forestry, and a host of other land use practices, cover more than 2 million square kilometers across China. Village lands tend to be managed at very fine spatial scales (≤ 30 m), with managers both adapting their practices to existing variation in soils and terrain (e.g., fertile plains vs. infertile slopes) and also altering soil fertility and even terrain by terracing, irrigation, fertilizing, and other land use practices. Relationships between fine-scale land management patterns and soil organic carbon (SOC) in the top 30 cm of village soils were studied by sampling soils within fine-scale landscape features using a regionally weighted landscape sampling design across five environmentally distinct sites in China. SOC stocks across China’s village regions (5 Pg C in the top 30 cm of 2 × 10 6 km 2 ) represent roughly 4% of the total SOC stocks in global croplands. Although macroclimate varied from temperate to tropical in this study, SOC density did not vary significantly with climate, though it was negatively correlated with regional mean elevation. The highest SOC densities within landscapes were found in agricultural lands, especially paddy, the lowest SOC densities were found in nonproductive lands, and forest lands tended toward moderate SOC densities. Due to the high SOC densities of agricultural lands and their predominance in village landscapes, most village SOC was found in agricultural land, except in the tropical hilly region, where forestry accounted for about 45% of the SOC stocks. A surprisingly large portion of village SOC was associated with built structures and with the disturbed lands surrounding these structures, ranging from 18% in the North China Plain to about 9% in the tropical hilly region. These results confirmed that local land use practices, combined with local and regional variation in terrain, were associated with most of the SOC variation within and across China’s village landscapes and may be an important cause of regional variation in SOC.     

Soil Organic Carbon Density in Hebei Province, China：Estimates and Uncertainty

In order to improve the precision of soil organic carbon (SOC) estimates, the sources of uncertainty in soil organic carbon density (SOCD) estimates and SOC stocks were examined using 363 soil profiles in Hebei Province, China, with three methods: the soil profile statistics (SPS), GIS-based soil type (GST), and kriging interpolation (KI). The GST method, utilizing both pedological professional knowledge and GIS technology, was considered the most accurate method of the three estimations, with SOCD estimates for SPS 10% lower and KI 10% higher. The SOCD range for GST was 84% wider than KI as KI smoothing effect narrowed the SOCD range. Nevertheless, the coefficient of variation for SOCD with KI (41.7%) was less than GST and SPS. Comparing SOCD‘s lower estimates for SPS versus GST, the major sources of uncertainty were the conflicting area of proportional relations. Meanwhile, the fewer number of soil profiles and the necessity of using the smoothing effect with KI were its sources of uncertainty. Moreover, for local detailed variations of SOCD, GST was more advantageous in reflecting the distribution pattern than KI.     

Methods to Estimate Aggregate Protected Soil Organic Carbon, 2: Does the Grinding of the Plant Residues Affect the Estimations of the Aggregate Protected Soil Organic Carbon?

A method to estimate the amount of soil organic carbon (SOC) physically protected within macroaggregates (>200 μm) consists of crushing soil samples and measuring the following SOC mineralization increase. This study investigated the effect of grinding the plant residues during soil crushing on the calculated amount of the protected SOC on two tropical soils (Arenosol and Ferralsol). Incubations of crushed and uncrushed soil samples amended with ground or unground plant residues were conducted. Our results showed that soil crushing increased SOC mineralization and that the presence of plant residues enhanced soil respiration also. The plant residues of the two soils had different decomposition rates, but grinding plant residues did not increase the amounts of cumulative carbon (C) mineralized after the 28 days of the experiment. We propose that the extra C mineralized after soil crushing is due to the breakdown of the soil structure and not to the grinding of plant residues.     

Spatial and Temporal Variability in Dissolved Inorganic Nitrogen Fluxes at the Sediment–Water Interface in Lake Illawarra, Australia

In this study, benthic flux measurements of inorganic nitrogen (i.e., $ {\text{NH}}^{ + }_{4} $ , $ {\text{NO}}^{ - }_{2} $ ?+? $ {\text{NO}}^{ - }_{3} $ ) were made using a batch incubation system at different stations (i.e., shallow sandy macrophyte and unvegetated beds, and deep central mud) over four seasons in Lake Illawarra, NSW, Australia, to study the influence of different primary producers (i.e., seagrasses, microphytobenthos (MPB) and macroalgae) and/or different sediment types (i.e., sand or mud) on the benthic fluxes. In general, nutrient fluxes displayed typical diel variations, with lower flux out of sediments (release) or enhanced uptake by the sediment in the light, due to the photosynthetic activities of the plant-MPB-sediment community in Lake Illawarra during photosynthetic periods. A distinct seasonal pattern of inorganic-N fluxes was also observed (e.g., the marked difference between summers 2002 and 2003). This may be explained by the seasonal variations in the biomass and activity (growing or decay phases) of MPB, seagrass and macroalgae, which may influence their nutrient assimilation and alter the chemical conditions of surface sediments that influence the benthic geochemical processes and thus benthic nutrient fluxes. On an annual basis, unvegetated sediments displayed net DIN effluxes, while seagrass beds showed a net DIN uptake, and the highest DIN uptakes coincided with the largest standing crop of seagrass and/or macroalgae and the highest levels of benthic community production. This may be due to the enhanced denitrification and/or assimilation activity by rooted plants and macroalgae, and the effect is most efficient during periods of net growth (e.g., in Spring 2002).     

Soil Organic Carbon,Phosphorous, and Potassium Status in Rice–Wheat Soils of Different Agro-climatic Zones in Indo-Gangetic Plains of India

The status of available macronutrients [phosphorus (P) and potassium (K)] and soil organic carbon (SOC) of the surface soil under a rice–wheat cropping system was studied in 40 districts of the Indo-Gangetic Plains (IGP) of India. The soil samples were collected from the farmers' fields in four transects (Trans-, Upper, Middle, and Lower Gangetic Plains) of the IGP. The selection of farmers, villages, blocks, and districts within an agro-climatic zone (ACZ) was done on the basis of a multistage statistical approach. The available macronutrients were characterized as low, medium, and high. In Trans-Gangetic Plains, SOC, available P, and available K were in the ranges of 0.06–0.86%, 6.7–85.1 kg ha^?1, and 50–347 kg ha^?1, respectively. In Upper Gangetic Plains, the respective values were in the ranges of 0.05–2.55%, 4.5–155.0 kg ha^?1, and 45 to 560 kg ha^?1. Similarly, in Middle Gangetic Plains, these values were in the ranges of 0.04–2.01%, 4.7–183.7 kg ha^?1, and 72–554 kg ha^?1, respectively. In Lower Gangetic Plains, respective values were 0.12–1.78%, 2.2–112.0 kg ha^?1, and 83–553 kg ha^?1. In Trans-Gangetic plains, the majority of the soils in the midplains ACZ representing intensively cultivated rice–wheat system area were low to medium in SOC and available P, whereas available K status was medium to high. Irrespective of the agroclimatic variations, more than 90% of the soils were low to medium in SOC and available P with a marginal deficiency of K. The majority of the coarse-textured soils in Shiwaliks were found to have low to medium SOC and available P, whereas less intensively cultivated arid zone soils were high in SOC, available P, and available K. In Upper and Middle Gangetic Plains, the majority of the soils tested medium for SOC and medium to high in available P and K. The dominance of medium status of available P in these soils could be due to mining of soil P by the rice–wheat cropping system practiced in these regions for more than 300 years. In Lower Gangetic Plains, the SOC was medium to high in most of the soils, whereas available P and K were high. Recent introduction of the rice–wheat system on intensive scale in these traditionally rice-growing areas resulted in less mining of SOC, P, and K.     

Re‐analysis of the Relationship between Organic Carbon and Loss‐on‐Ignition in Soil

The suitability of loss‐on‐ignition (LOI) as an alternative to direct measurement of organic carbon (OC) has been debated for decades without resolution. The literature contains an abundance of different linear regression models to describe the LOI–OC relationship, most based on untransformed values of LOI and OC. Such regression is suspect because the variables are unable to occupy Euclidean space. Logratio transformation—based on relative rather than absolute differences—eliminates this constraint. Re‐analysis of the relationship on new and 10 previously published datasets using logratio techniques reveals that the relationship is nonlinear and that the profusion of regression models is in part a function of the range of LOI. Although LOI may offer a crude estimate of OC at high LOI levels, OC/LOI ratios when LOI is less than about 25% are too variable for reliable OC estimation, and interstudy comparisons remain dubious. Direct measurement of OC is recommended.     

Crop Residue Retention and Nutrient Management Practices on Stratification of Phosphorus and Soil Organic Carbon in the Soybean–Wheat System in Vertisols of Central India

The long-term crop residue retention coupled with external nutrient inputs are crucial for maintaining soil phosphorus (P) and soil organic carbon (SOC) in Vertisols of Central India. A study was conducted to evaluate the long-term effect of three wheat residue management practices (residue burning, incorporation, and surface retention) in combination with three supplementary nutrient inputs (SNI) [control, fertilizer, and farmyard manure (FYM)] on stratification of P and SOC in the soybean–wheat system in Vertisol. The wheat residue either incorporated or retained on the soil surface increased the availability of P and SOC content as compared to the common practices of residue burning. Residue retention or incorporation increased stratification of P and soil organic carbon over the residue burning. Irrespective of the nutrient treatments, greater stratification ratio of SOC and P were registered under wheat residue incorporation or retention compared to residue burning. It is evident from the study that wheat residue incorporation or retention plus addition of FYM could be an effective strategy for increasing the soil fertility in a soybean–wheat system of Vertisols of Central India.     

National-Scale Meta-Analysis of Soil Carbon and Nitrogen Accumulation Potential in China’s Grain for Green Program

Eurasian Soil Science - Grain for Green Program (GFGP) by establishing revegetation on degraded cropland has been considered effective to capture soil carbon (C) in terrestrial ecosystems. However,...     

Dry Atmospheric Contribution to the Plant–Soil System Around a Cement Factory: Spatial Variations and Sources—a Case Study from Oman

The present study determines the source of dust particles and investigates their impact on the chemical compositions of plants and soils around a cement factory in Oman within a radius of 10 km of this disturbed ecosystem. A total number of nine samples of the species of plants (Rhazya stricta), nine samples of soils, and nine samples of dust were collected and analyzed for major ions and trace elements including rare earth elements (REEs). Principal component analysis applied to the major and trace element concentrations in the dust indicated the input of at least two sources to the dust in the study area: ophiolites and cement. The REE distribution in the plants and soils revealed that the most available elements to plants originated dominantly from ophiolites rather than from cement. The contribution of cement industry is significant only in the zone located at about 0.500 to 2 km around the cement factory, whereas the contribution of ophiolites increases with distance from the cement factory.     

The Use of the Soil-Geomorphological Database for Studying the Spatial Variability of the Humus Content,Physical Clay,and Clay in the Soils of the Kuznetsk–Salair Geomorphological Province

Eurasian Soil Science - Based on archival data on the soils of the Kuznetsk–Salair geomorphological province (within Novosibirsk oblast) and the results of processing digital elevation...     

Design and Applicationos of Land Resources and Ecological Environment Information System： A Case Study of Zigui County in the Three Gorges Area of China

The design and applications of a land information system built upon ARC/INFO and ArcView are presented.The proposed system not only maintains all the advantages of the more conventional implemen-tations but also enhances them in the following ways:1)the application program interfaces(API)are used to transmit data and messages among different parts of the system;2)the integrated system can support studies on land evaluations and ecological analyses by efficient management of attribute and spatial data and 3)correspondingly,spatial records and attributive records are linked by the same identifiers(ID).A case study application in Zigui County of the Three Gorgas Area in China demonstrates that the system could employ land-use maps and land property data to predicate and analyze the land utilization changes in the past,present and future.The ecological environment analysis can be carried out with the data of land,economics and terrain map used,showing that the system can be widely applied,especially to survey land and environment resources in the countryside area.     

Evaluation of Soil Fertility Quality Variation During Past 30 Years in a Major Grain-producing Region of the North China Plain——A Case Study of Yucheng County

土壤肥力质量的时空演变分析有助于了解区域土壤肥力变化情况和变化规律,对制定相应的农业管理措施,进一步提升土壤生产力,稳定粮食产量具有重要意义.本文以华北平原典型区禹城市为例,进行了土壤肥力质量时空演变分析.结果表明:自1980年以来,经过近30年的耕作和中低产田改造,禹城市土壤肥力质量显著提高,尤其在土壤肥力质量较差的区域,土壤质量捉升更显著;土壤肥力质量空间变异性减弱,土壤肥力水平趋于一致,且空间变异受自然因素的影响降低,更多的受到人为管理因素的影响.     

Concentrations and Availability Indicators of Soil Heavy Metals; the Case of Children’s Playgrounds in the City of Athens (Greece)

This study reports on the concentrations, distribution, and availability of heavy metals in the children’s playground soils of Athens. Playgrounds were chosen because they are open city areas; they show relatively even spatial distribution within the district of Athens and are used by a great number of young children and their escorts on a regular basis. Samples were collected from 70 playground surface soils, representing more than 70% of the city’s playgrounds. Cu, Zn, Pb, Cr, Ni, Co, Mn, and Fe were extracted by aqua regia and by diethylene triamine pentaacetic acid (DTPA) to estimate total and available metal forms, respectively. Their mean total concentrations were 43, 174, 110, 80, 82, 22, 312, and 17?×?10³?mg kg^?1, respectively. The DTPA-extracted fraction showed much lower values, with means of 2.5, 7.8, 5.8, 1.5, 1.3, 0.4, 8.4, and 2.0 mg kg^?1 respectively, which, however, should be carefully monitored since they relate directly to the bioavailable fraction of heavy metals. Though mean values of metal concentrations are not particularly high, the calculated enrichment factors indicate site-specific cases of high enrichment with heavy metals. Considering that the bioavailable fraction of a metal is possibly a more appropriate indicator for the recent soil pollution history, availability ratios were calculated and their distribution was visualized over the entire city profile using the appropriate GIS software. It was shown that recent metal pollution events appear to have affected mostly playground sites in the southern and eastern part of the municipality.     

Effect of Organic Residues with Varied Carbon–Nitrogen Ratios on Grain Yield,Soil Health,and Nitrous Oxide Emission from a Rice Agroecosystem

Experiments were conducted in an attempt to study the impact of using different organic residues as fertilizers on grain yield, magnitude of nitrous oxide (N₂O) emissions, and soil characteristics. Five fertilizer treatments including conventional nitrogen (N) fertilizer, cow manure, rice straw, poultry manure, and sugarcane bagasse were applied in the rice field in 2012. The maximum reduction in seasonal N₂O emissions (10–27%) was observed under the influence of rice straw application over conventional N fertilizer. The experiment was repeated for a second season in 2013 with the same treatments for further confirmation of the results obtained during the first year of experimentation. The application of rice straw also showed a slight advantage by increasing grain yield (4.38 t ha^?1) compared to control. Important soil properties and plant growth parameters were studied and their relationships with N₂O emission were worked out. The incorporation of organic residues helped in restoring and improving the soil health and effectively enhancing grain yield with reduced N₂O emission from rice fields.     

Spatial distribution,food chain translocation,human health risks,and environmental thresholds of heavy metals in a maize cultivation field in the heart of China’s karst region

Journal of Soils and Sediments - The overexploitation of resources such as mining and metallurgical and agricultural resources has resulted in heavy metal accumulation and soil acidification....     

Investigation of Soil Concentrations of Persistent Organic Pollutants, Trace Elements, and Anions Due to Iron–Steel Plant Emissions in an Industrial Region in Turkey

The spatial distribution of several air pollutants emitted from iron–steel industries in Hatay-Iskenderun industrial region in Turkey was investigated by measuring their concentrations in soil. Collected soil samples (n?=?20) were analyzed for persistent organic pollutants (POPs; i.e., polycyclic aromatic hydrocarbons, polychlorinated biphenyls, polybrominated diphenyl ethers, and polychlorinated naphthalenes), anions, and trace elements. Generally, all measured POP concentrations and marker trace elements for iron–steel industry (Zn, Pb, and Cu) were high relative to those reported previously for rural and urban areas around the world, and they were comparable to those measured recently in a similar industrial region (Aliaga, Izmir, Turkey). For all investigated POPs, elements, and anions, the highest concentrations were measured at points located north of the iron–steel industries where their emissions are transported by the prevailing southerly winds. The spatial distribution and levels of POPs, elemental, and anionic concentrations indicated that the iron–steel plants in Hatay-Iskenderun region are important sources for these pollutants. Statistically significant relationships between several organic and inorganic pollutants further confirmed that they are emitted by common sources (iron–steel plants).     

Integrated Evaluation of Ecological Security at Different Scales Using Remote Sensing： A Case Study of Zhongxian County,the Three Gorges Area, China

Based on related literature and this research, an ecological security evaluation from the pixel scale to the small watershed or county scale was presented using remote sensing data and related models. With the driver-pressure, state and exposure to pollution-response （DPSER） model as a basis, a conceptual framework of regional ecological evaluation and an index system were established. The extraction and standardization of evaluation indices were carried out with GIS techniques, an information extraction model and a data standardization model. The conversion of regional ecological security results from the pixel scale to a small watershed or county scale was obtained with an evaluation model and a scaling model. Two conceptual scale conversion models of regional ecological security from the pixel scale to the county scale were proposed： 1） scale conversion of ecological security regime results from plxel to small watershed; and 2） scale conversion from pixel to county. These research results could provide useful ideas for regional ecological security evaluation as well as ecological and environmental management.