Gan-Lin Zhang

Pedogenic evolution of paddy soils in different soil landscapes

Paddy soils are Hydragric Anthrosols and are an important soil resource for food production. They are widely distributed in China and Asia. Soils that can be used for paddy cultivation vary considerably but basically are grouped into three kinds of landscape, i.e., well-drained sloping uplands, alluvial plains with groundwater fluctuation, and poorly drained polder areas with a near-surface water table. Typical soil chronosequences were studied to clarify the pedogenic changes after wetland rice cultivation, especially in relation to management practices. All of them are in important rice production regions of China. The study focussed on redox condition and iron oxides dynamics. On alluvial plains, the soil conditions range from continuously reducing controlled by high groundwater to alternating reduction and oxidation because of artificial submergence and groundwater fluctuations. Artificially induced leaching losses, previously prevented by a high groundwater table, are partly compensated during paddy cultivation by the rejuvenation process of alluvial deposition. Soils on an older delta, which no longer receives river-sediments, are more strongly developed and showed a decrease of DCB-extractable iron in surface horizon of young paddy soils and more profoundly throughout the profile in old paddy soils. In the polder area, the apparent lowering of groundwater table by deposition of sediment has changed the soil hydrology and increased redox potential. With the better soil aeration, crystalline iron oxides and their ratio to total iron increase with cultivation age. On well-drained terraces, the change of soil moisture regime is overwhelming. Previously well-aerated upland soils are periodically reduced, which accelerates leaching and loss of iron oxides from surface horizons, and probably clay decrease by lateral movement and ferrolysis processes superimposed on the difference of parent soils. An iron-enriched subsurface horizon has formed rapidly and it is a diagnostic feature of this type of paddy soil.

GlobalSoilMap.net – a new digital soil map of the world

Knowledge of the world soil resources is fragmented and dated. There is a need for accurate, up-to-date and spatially referenced soil information as frequently expressed by the modelling community, farmers and land users, and policy and decision makers. This need coincides with an enormous leap in technologies that allow for accurately collecting and predicting soil properties. We work on a new digital soil map of the world using state-of-the-art and emerging technologies for soil mapping and predicting soil properties. The global land surface will be mapped in 5 years and the map consists of the primary functional soil properties at a grid resolution of 90 by 90 m. It will be freely available, web-accessible and widely distributed and used. The maps will be produced by a global consortium with centres in each of the continents: NRCS for North America, Embrapa for Latin America, JRC for Europe, TSBF-CIAT for Africa, ISSAS for parts of Asia and CSIRO for Oceania. This new global soil map will be supplemented by interpretation and functionality options that aim to assist better decisions in a range of global issues like food production and hunger eradication, climate change, and environmental degradation. In November 2008, a grant has of US

Origin and development of soil science in ancient China

18 million has been obtained from the Bill & Melinda Gates foundation to map most parts in Sub-Sahara Africa, and make all Sub-Saharan Africa data available. From this grant there are funds for coordinating efforts in the global consortium.

Phosphorus-enriched soils of urban and suburban Nanjing and their effect on groundwater phosphorus

Based on many ancient records, archaeological discoveries, and current studies, knowledge of soils including their classification, distribution, and utilization was understood 2000 years ago in China. Thus, pedology may have originated in China. A brief history of Chinese thoughts about soils is described along with the development of their farming experiences since ancient times. Even today, people still get useful information from these old records and works.

Precise estimation of soil organic carbon stocks in the northeast Tibetan Plateau.

Neither the phosphorus (P)-rich soils in urban areas nor their environmental implications have been adequately studied. This study investigated soils of typical urban function zones in Nanjing/ China, like park, residential areas, school yards, campus as well as suburb vegetable land and garbage filling sites, and meantime ground water in situ. Typical soils were also experimentally leached for P leaching evaluation. All studied soils were enriched with P with enrichment ratios varying from 2 to 10 for total P and 5 to 22 for NaHCO 3 -extractable P, as compared with the original parent soils. The C : P ratios also indicated strong enrichment of P in urban soils. In urban areas the maximum P layer appeared as buried under different depth while in suburban soils as epipedon. The various morphology of P distribution suggested different soil formation patterns, which were related to the land use history. Groundwater P was significantly correlated with the maximum extractable P content of P in soil profiles and even better with the weighted average P content of the whole profile or P content of the soil layer at or close to groundwater table. Dissolved P in experimental leachate was comparable with that of groundwater but higher than environmentally acceptable level. Furthermore, there was a significant correlation between solution P and different extractable P forms of the studied soils. Simple P tests can provide an evaluation of the potential risk of urban soils in discharging P to water system.

Mapping Soil Texture of a Plain Area Using Fuzzy-c-Means Clustering Method Based on Land Surface Diurnal Temperature Difference

There is a need for accurate estimate of soil organic carbon (SOC) stocks for understanding the role of alpine soils in the global carbon cycle. We tested a method for mapping digitally the continuous distribution of the SOC stock in three dimensions in the northeast of the Tibetan Plateau. The approach integrated the spatial distribution of the mattic epipedon which is a special surface horizon widespread and rich in organic matter in Tibetan grasslands. Prediction models resulted in high prediction accuracy. An average SOC stock in the mattic epipedon was estimated to be 4.99 kg m−2 in a mean depth of 14 cm. The amounts of SOC in the mattic epipedon, the upper 30 cm and 50 cm accounted for about 21%, 80% and 89%, respectively, of the total SOC stock in the upper 1 m depth. Compared with previous estimates, our approach resulted in more reliable predictions. The mattic epipedon was proven to be an important factor for modelling the realistic distribution of the SOC stock in Tibetan grasslands. Vegetation-related covariates have the most important influence on the distribution of the mattic epipedon and the SOC stock in the alpine grassland soils of northeast Tibetan Plateau.

Distribution and migration of heavy metals in undisturbed forest soils: A high resolution sampling method

The use of landscape covariates to estimate soil properties is not suitable for the areas of low relief due to the high variability of soil properties in similar topographic and vegetation conditions. A new method was implemented to map regional soil texture (in terms of sand, silt and clay contents) by hypothesizing that the change in the land surface diurnal temperature difference (DTD) is related to soil texture in case of a relatively homogeneous rainfall input. To examine this hypothesis, the DTDs from moderate resolution imagine spectroradiometer (MODIS) during a selected time period, i.e., after a heavy rainfall between autumn harvest and autumn sowing, were classified using fuzzy-c-means (FCM) clustering. Six classes were generated, and for each class, the sand (> 0.05 mm), silt (0.002–0.05 mm) and clay (< 0.002 mm) contents at the location of maximum membership value were considered as the typical values of that class. A weighted average model was then used to digitally map soil texture. The results showed that the predicted map quite accurately reflected the regional soil variation. A validation dataset produced estimates of error for the predicted maps of sand, silt and clay contents at root mean of squared error values of 8.4%, 7.8% and 2.3%, respectively, which is satisfactory in a practical context. This study thus provided a methodology that can help improve the accuracy and efficiency of soil texture mapping in plain areas using easily available data sources.

Development of the soil research about urban, industrial, traffic, mining and military areas (SUITMA)

Abstract The vertical distribution and migration of Cu, Zn, Pb, and Cd in two forest soil proflles near an industrial emission source were investigated using a high resolution sampling method together with reference element Ti. One-meter soil proflle was sectioned horizontally at 2 cm intervals in the flrst 40 cm, 5 cm intervals in the next 40 cm, and 10 cm intervals in the last 20 cm. The migration distance and rate of heavy metals in the soil proflles were calculated according to their relative concentrations in the proflles, as calibrated by the reference element Ti. The enrichment of heavy metals appeared in the uppermost layer of the forest soil, and the soil heavy metal concentrations decreased down the proflle until reaching their background values. The calculated average migration rates of Cd, Cu, Pb, and Zn were 0.70, 0.33, 0.37, and 0.76 cm year −1 , respectively, which were comparable to other methods. A simulation model was proposed, which could well describe the distribution of Cu, Zn, Pb, and Cd in natural forest soils.

Formation, characteristics and eco-environmental implications of urban soils – A review

Abstract The share of urban population of the world is expected to reach 75% by around 2050. The need to offer within the cities soil services rose awareness of keeping soil functions in cities. Parallel to strong growth of cities some cities are shrinking. In cope with this, working groups (WG) of urban soils have been established (AK Stadtboeden1987, Germany, ICOMANTH 1995, USA, and internationally the IUSS WG US/SUITMA 1998 (Urban Soils/Soils of Urban, Industrial, Traffic, Mining and Military Areas)).The first attempts at urban soil surveys involved municipal waters and sewers in the USA in the 1970s. In the 1990s, the soils of about 15 cities were mapped, totally or in part, in Germany, and in the USA in Baltimore, and recently in New York. But at all times the soil pollution was a main interest of urban soil investigation. Urban soils are characterized by their particular use on which first attempts of soil classification are based. As knowledge about soil morphology and soil composition increased, soil survey concepts were developed. These concepts take into account relicts of the original, natural soils, as well as new, man-modified and man-made materials. At least in humid climate Regosols, as well as other urban soils such as Carbonatosols, Dialeimmasols, Intrusols, Reductosols and Acid Sulfuric Soils, can develop within 25 years or less. Technosols as soils from man-made materials are already included in the WRB. Besides pollution, a major feature of urban soils is soil sealing by construction. This restricts the availability of soils for urban greenery and other functions. Some particular problems of urban soils are high stone content, high differences of bulk density, shape of particles and soil structure performance. This lowers the quality of soils to fulfill functions. Specific methods are necessary to determine many urban soil characteristics. Specific instructions have been developed for soil and soil sealing surveys, and stormwater infiltration. However, for other cases, feasible methods are still missing. The European Commission’s “Thematic Strategy of Soil Protection” did raise political awareness of urban soils, with a main focus on sealing.

Modeling spatio-temporal distribution of soil moisture by deep learning-based cellular automata model

Abstract Soils in urban areas have versatile functions, and their ecological services, especially the ability to buffer and purify pollutants, are very much needed. However, the formation and characteristics of urban soils are strongly affected by human activities, and so are their functions. In urban areas, soil horizons are often irregularly established, with anthropogenic layers and a high degree of heterogeneity owing to human disturbance and infill. Soil structure is often under degradation due to artifacts and technogenic substrata, mechanical compaction and human trampling. Physical degradation, such as compaction and destruction of structure, may reduce the ability of urban soils in infiltrating water and storing capacity, thus causing a higher runoff and pollutant load to the receiving water bodies. Soil compaction is also believed to worsen city heat island effects by reflecting more radiation, and seriously reduce the soil gas capacity and exchange. However, soil sealing fully loses its service function, further deteriorating urban ecology and environment. Enrichment of various waste materials associated with human activities, including nutrient elements, heavy metals and organic pollution, is the major problem of the urban soil environment. Materials containing rich liming in the urban soils lead to alkaline soil conditions, which can change element speciation and activities. The main features of urban soil contamination are characterized by strong accumulation of so-called “urban elements” such as copper (Cu), zinc (Zn), lead (Pb) and mercury (Hg), but less accumulation of other heavy metals. During the process of urban development, heavy metal contamination of urban soils not only happens nowadays, but also did in the past, especially when primitive mining and metal processing prevailed. Furthermore, urban soils are often polluted by organic pollutants, especially polycyclic aromatic hydrocarbons (PAHs). Platinum group elements (PGE), especially platinum (Pt), palladium (Pd) and rhodium (Rh) from automobile exhaust catalysts, are also accumulated in urban soils as affected by traffic. Physical and chemical degradation decrease soil enzymes and microbial activities, especially in industrial zones with high concentrations of heavy metals, low concentrations of organic matter and serious compaction. Unfortunately, the evolution of urban soil and attenuation of ecological function are believed to ultimately harm human welfare. Therefore, it is very important to establish a risk assessment system for better management of urban soil resources.