南京市近20年城镇用地扩展对土壤资源数量和质量的影响

应用RS和GIS技术，基于1984年、1995年、2000年和2003年等四个时期的TM卫星遥感空间数据，采用多时相连续对比法分析了南京市过去20年来城市化与城镇扩展过程；同时，以南京市土壤图、全国第二次土壤普查数据为基础，并结合补充调查和采样分析数据，对南京市城镇扩展过程中土壤资源动态变化进行了研究。结果表明：过去20年南京市城市化发展速度较快，2003年全市城镇建成区面积较1984年增长近1倍；由于城镇规模的快速扩展，全市土壤资源总面积缩减7．4％，且城镇周边地区农业基础设施好、生产力水平较高的土壤资源缩减比例较大，对区域农业生产和粮食安全产生了不容忽视的影响。     

Multiple effects of urbanization on the biodiversity of developing countries: The case of a fast-growing metropolitan area (Concepción, Chile)

Urbanization is increasingly homogenizing the biota of less developed countries. Even though urban sprawl is a worldwide problem, most studies on the effects of urbanization, and the conceptual models have focused on developed countries. South America has not escaped urbanization, and here we discuss the potential impacts of urban sprawl with respect to three ecosystems in the metropolitan area of Concepción, Chile. We consider this area a good model and fairly representative of other cities in developing countries which are also experiencing rapid and uncontrolled growth. We found that the impacts of urban sprawl on biodiversity in the metropolitan area of Concepción differ little from cities in other parts of the world: native ecosystems are replaced by pavements and buildings and what is left of the natural soil is covered with green areas dominated by non-native ornamental species. Wetlands and other peri-urban ecosystems are rapidly being destroyed, fragmented or invaded by non-native species. We found that from a study area of 32,000 ha, there was a net loss to urbanization of 1734 ha of wetlands (23% of the original) and 1417 ha (9%) of agricultural, forest and shrub land cover types between 1975 and 2000. From the total area urbanized (3151 ha), 55% corresponded to wetlands and 45% to agricultural, forest and shrub lands cover types. We see the lack of environmental awareness as a major cause of the increasing deterioration of biodiversity in urban areas of developing countries. More research is needed to fully understand the effects of urban sprawl on the biodiversity of developing countries to include these ecosystems in global conservation strategies.     

Measurement of urbanization process and the paddy soil loss in Yixing city,China between 1949 and 2000

This study used GIS technology, remote sensing images of 1949, 1966, 1981, 1984, 1988, 1992, 1996 and 2000, to analyze the spatial process of urbanization and its impact on the soil resources in Yixing city, southeast China. The results showed that the urban area grew more than three-fold during 51 years and the loss of paddy soil accounted for 82.9% of all soil loss. According to the expansion dynamics and the results of spatial metrics, the urban expansion process in Yixing could be divided into four steps, the initial step (1949–1966), the almost standstill step (1966–1981), the preparation step (1981–1984) and the rapid growing step (after 1984). The study also indicated that the urban expansion was encouraged by the transportation system, however, restricted by the rivers, lakes and hills. The local government's decision also affected the spatial process of urban expansion. The spatial process of Yixing urban expansion might reflect the spatial process of urbanization of southeast China, the region with a rapidly growing economy.     

近20年来南通市区城镇用地扩展遥感监测

借助RS和G IS技术,利用TM卫星影像资料对近20年来南通市区城镇用地扩展过程进行了研究。结果表明,1984~2003年主城区扩展趋于缓慢,市区边缘带乡镇扩展速度加快。在扩展模式上,主城区先是沿着老城区填充式零星的扩展,然后逐步与周边乡镇连成一片,并形成新的扩展中心。城镇用地扩展的主要驱动力是工业化水平的提高。把市区城镇用地扩展图与土壤图相叠加,并参照1987年土地利用现状调查资料,结果表明南通市区城镇用地扩展主要侵占城市周边优质的菜地和农田。     

Rapid urbanization in China: A real challenge to soil protection and food security

To feed its 1.3 billion population with a per capita cultivated land far below the world average, China is already facing a great challenge of land scarcity. Accelerated urbanization along with explosive economic growth has further worsened the shortage of agricultural land over the last two decades. Increasing concern over land is expressed in terms of soil availability for grain production and soil quality degradation. Based on official statistics and data derived from satellite imagery, dynamics of China's cultivated land over the past two decades is outlined and the causes and destinations of cultivated land loss are analyzed in this paper. Particularly, urbanization-related land-use changes and their spatial variation across the country are demonstrated. Furthermore, impacts of urbanization and associated waste disposals, consequent shifts of soil utilization on areal soil quality are expatiated. It is initially concluded that China's cultivated land is shrinking at a rather shocking rate. Although conversion to urban and industrial uses took up a comparatively small share of total cultivated land loss, urbanization should still be considered as a great threat to future agricultural production for several reasons. Urbanization is increasing the risk of soil pollution through waste disposal and acid deposition derived from urban air pollution. Facing rapid urbanization, China is making positive policy responses to the challenge of decreasing availability of cultivated land and offering unremitting efforts towards the goal of national food security.     

基于RS和GIS苏州市近20年来城镇扩展对土壤资源的影响研究

随着城市化的加速发展,越来越多的土壤资源被侵占。本文借助RS和GIS技术,利用1984、1995、2000、2003年4期TM卫星遥感影像,采用多时相连续对比法对苏州市近20年来城镇扩展情况进行了分析;结合苏州市土壤图和全国第二次土壤普查数据,对苏州市近20年来城镇扩展占用土壤资源的情况进行了研究;并初步提出城镇扩展对粮食安全的影响。     

基于遥感评价城市扩张对耕地质量等级结构及产能的影响

快速的城市化过程占用大量的优质耕地资源,引发耕地质量下降和产能损失已成为中国耕地保护面临的重要问题。该文利用遥感影像和耕地质量等级数据评价了近30 a来江苏城市扩展对耕地质量和产能的综合影响。研究发现江苏的城市扩张迅速,因城市建设引起的耕地损失约占耕地总量的7%。其中被占用耕地中以优质耕地为主,一、二、三等级耕地约占60%。从质量等级结构上来看,耕地质量结构有恶化的趋势,表现在一、二、三等优质耕地比例下降1.5%,而四、五、六、七等劣质耕地同比例上升。耕地数量和质量的同步降低引起生产能力下降14%。城市占用农地对耕地质量和生产能力的综合影响应该给予足够的重视。     

城市化对郑州市土壤功能演变的影响

城市化快速发展不仅造成了自然土壤面积和类型的缩减，也导致土壤功能发生变化并通过土地利用方式的变化表现出来。本文以郑州市为例，通过研究城市扩张和土地利用变化来探讨城市化过程中土壤功能演化特点。研究结果表明：在过去的20年间，随着城市化的发展，土地利用结构发生着剧烈变化，城市建设面积不断扩张，水稻土土类和盐化潮土亚类消失，另外伴随还消失了2个土属和11个土种，一些特定的土壤功能消失；伴随着土地利用变化，土壤主要从生产功能、生态功能向土壤承载功能转换，其次为生态功能向生产功能转化。土壤功能这样的转换不仅增加了区域农业生产压力，也可能对区域生态环境产生不可忽视的影响。     

城市化过程对土壤资源影响研究进展

世界范围内的快速城市化过程对土壤资源的质与量都产生了深刻影响.作为一种不可再生性自然资源,土壤在我国快速城市化过程中的强烈人为活动影响下发生功能上的转化、弱化甚至消失.城市及其周边地区的土壤景观、各种土壤过程都明显异于传统的土壤质量演变规律.与农业生态系统相比,城市生态系统更加复杂,城市化过程中土壤演变研究的挑战性也更大.深入开展城市化过程中土壤质、量响应及其生态环境效应的系统研究意义重大.     

How does the conversion of land cover to urban use affect net primary productivity? A case study in Shenzhen city, China

China has made great economic achievements since the Reform and Opening policy implementation. Shenzhen as the representative city has experienced rapid urbanization and population growth. Urbanization strongly changes the nature of the land surface and has a large influence on the regional ecosystems. In the process of urbanization, fertile cropland and original forest are often destroyed. It is important to regularly monitor the effect of urbanization on the natural environment so as to allow us to control the encroachment to a reasonable extent. Net primary productivity (NPP) is an important productivity indicator of the ecosystem. We obtained land covers from Landsat TM images to quantify urbanization of Shenzhen between 1999 and 2005. We used the Moderate Resolution Imaging Spectroradiometer (MODIS-based) Normalized Difference Vegetation Index (NDVI) data, Landsat-based land cover map, meteorological data and other field data to drive the CASA productivity model and obtain net primary productivity for the study area. Finally, we estimated the effect of urban sprawl on regional NPP. The study on Landsat-based land cover maps indicated that a move towards urban is the most significant landscape change in Shenzhen City and urbanization has irreversibly transformed about 20.21% of Shenzhen's surface during 1999–2005. NPP loss mainly resulted from urbanization during 1999–2005 and totaled to 321.51 Gg of carbon, an average annual reduction of 45.93 Gg of carbon. For every square km of Shenzhen area, NPP was on average reduced by 0.0017 Gg of carbon during 1999–2005. The loss of NPP is equivalent to a reduction in absorption of 520.85 Gg CO₂ and release of 385.81 Gg O₂, so urbanization has a large influence on the regional net primary productivity.     

Establishing a spatial grouping base for surface soil properties along urban–rural gradient—A case study in Nanjing,China

Conventional classification systems based on vegetation and land use are frequently used to characterize or describe urban soils to determine the influence of urbanization on soils. In this study, the sensitivity of different grouping methods in reflecting soil variations along an urban–rural gradient was compared. The objective of this study was to determine the most sensitive grouping system in depicting and explaining variations of soil attributes around an urban area. Grouping methods, including urban–rural division, in situ vegetation type, land use types in different scales and numerical clustering, were compared for both single soil attributes and “soil set” defined by multiple variables. The result shows urbanization has a strong impact on many soil properties, especially that of gravel content, sand content, pH, phosphorus and soil compaction. In terms of the variations of soil attributes, in situ vegetation type is the most sensitive in comparison with local land use types and district-viewed land use types. In other words, soil properties in this study are not sensitive to coarser spatial resolution. Therefore, it's hard to interpret the spatial variation of urban soil by regular methods using natural soil-landscape paradigm. Furthermore, vegetation would best proxy the delineation of single attribute of urban soils. Numerical clusters effectively reflect the land use types and their change during urbanization. All clusters were interpreted as different sets with practical meanings: soil in abandoned greenbelt, soil in ill-managed greenbelt, soil in new vegetable land, extreme urban conditioned soil, soil in well-managed greenbelt, soil in highly mellowed vegetable land, soil in common urban–peri-urban greenbelt and weak-urban-impacted soil. They can be used as bases for soil regionalization in urban and peri-urban environment.     

The long‐term soil phosphorus balance across Chinese arable land

Quantifying temporal and spatial variation of soil phosphorus (P) input, output and balance across Chinese arable land is necessary for better P management strategies. Here, we address this challenge using a soil P budget to analyse the soil P balance in arable land across the whole of China, for the period 1980–2012. Results indicated that the total P input to soil increased from 22.5 kg P/ha in 1980 to 79.1 kg P/ha in 2012. However, the total P output from soil only increased from 17.9 kg P/ha in 1980 to 36.9 kg P/ha in 2012. Therefore, the average net soil P surplus in China increased from 4.6 kg P/ha in 1980 to 42.1 kg P/ha in 2012. Our research found great variation in soil P balances across different regions. Soil P balance varied between regions with the order of southeast (SE) > north central (NC) and the middle and lower reaches of Yangtze River (MLYR) > southwest (SW) > northwest (NW) > northeast (NE). Phosphorus that has accumulated in agricultural soil across China could theoretically meet crop P demands for approximately 4.8–12.0 yrs, depending on the bioavailability of P stored in soils. Increasing the return rates of manure and straw could substantially reduce the demand for fertilizer‐P. This paper represents a basis for more targeted, regionally informed P fertilizer recommendations in Chinese soils.     

Evaluating the applicability of the water erosion prediction project (WEPP) model to runoff and soil loss of sandstone reliefs in the Loess Plateau,China

Soil erosion is one of the most serious environmental issues, especially in vulnerable areas such as the Pisha sandstone regions located in the Loess Plateau (China). In these types of reliefs, long-term studies monitoring runoff and soil loss are scarce, and even more considering the efficiency of different soil management techniques applied to reduce land degradation. In this study, seven years (2014–2020) of in-situ measurements of surface runoff and soil loss for different land uses (forestland, shrubland, grassland, farmland, and bare land) in a Pisha Sandstone environment at the Loess Plateau were conducted. We applied the Water Erosion Prediction Project (WEPP) model combining the large database with the precipitation regimes. Our results showed that runoff volume coming from observed and simulated data exhibited significant differences among them depending on the different vegetation types. Runoff and soil loss were different among diverse land use types as follows: farmland > grassland > shrubland > forestland. After conducting a calibration, we found satisfactorily simulated surface runoff and sediment yield based on precipitation regimes and land uses at sandstone reliefs. Simulation performance of surface runoff was better than sediment yield. The range of standard error of the model simulation for event and annual values of runoff were 4.71 mm and 12.19 mm, respectively. The standard error for event and annual values of soil loss were 4.19 t/hm² and 21.86 t/hm². In the calibration group, R² of runoff and soil loss were 0.92 and 0.86 respectively, while Nash-Sutcliffe coefficient (E) reached 0.90 and 0.85, respectively. In the validation group, the R² for both runoff and soil loss were 0.82 and 0.56, respectively. Nash-Sutcliffe coefficient (E) were 0.77 and 0.54 for the runoff and sediment yield. We concluded that using a detailed monitoring dataset, the WEPP model could accurately simulate and predict water erosion in the hillslopes of Pisha sandstone area.     

Assessment of deforestation impact on soil erosion in loess formation using 137Cs method (case study: Golestan Province,Iran)

Golestan, a province in the North-East of Iran, is characterized by high coverage of loess deposits. Since 1963, the area has experienced approximately 200,000 ha deforestation due to land-use changes in agriculture and increasing demand for wood. Approximately, 110,000 ha of the clear-cut lands are under dry-farming, mainly for wheat cropping, and about 86,000 ha have been reforested. This IAEA funded project is the first attempt to use nuclear techniques in the East of Hircanian Forest for determination of on-site impacts of deforestation due to two land-use changes (i.e. dry farming and reforestation). Practicing long-term dry-farming led to 60% soil losses with a mean rate of 2 mm per year. The net erosion rate of croplands on loess deposits in the study area was 32.27 t ha⁻¹ yr⁻¹. Reforestation, cultivation of even-aged Cypress trees since 1993, showed 13 to 60 percent effectiveness in soil conservation. Dry-farming land use resulted in the loss of 95 t ha⁻¹ soil organic carbon (SOC) stock at a mean rate of 1.7 t ha⁻¹ over 54 years. Cultivating Cypress trees successfully restored the SOC content by 100% compared with the SOC in original forests. The conversion of dry-farming lands to orchards of olive trees since 2004, brought more income for farmers but were less effective in soil conservation because of low canopy cover of olive trees. Our data provide key information and guidance for land users and decision-makers about implementing strategic and sustainable conservation practices to restore degraded land.     

京郊卫星城区域农村居民点土地利用特征分析

分析大城市卫星城区域农村居民点用地的利用特征及其空间布局,有助于更好地了解农村居民点用地的结构与功能变化。该文选择北京市重点建设的卫星城顺义区为研究区,以第二次全国土地调查数据为基础,运用计量地理模型与GIS技术相结合的方法,对农村居民点用地及其内部结构进行了分析。分析结果表明：反映农村产业经济活动的工业用地、仓储用地成为农村居民点重要的用地组合类型,农村居民点内部用地类型丰富,部分镇区内的农村居民点用地中工业用地占据绝对优势。农村居民点利用空间差异显著,区位作用突出。中西部区域的农村居民点平均规模偏大,区位指数和多样化指数较高;而稳定性指数表现出自西向东逐渐提升的格局,但在空港物流经济影响下的农村居民点用地的稳定性较高,用地形态相对规整。顺义区农村人口与农村居民点在空间上的分布明显脱节,大量农村人口聚集于城镇边缘地带,该区域农村工业化倾向突出,农村人口基本上已经脱离了传统的农业生产。农村居民点用地及其内部结构特征体现出不同生产力发展水平,农村产业发展已成为推动农村居住与生产空间形态发生变化的最直接的动力。研究结论表明,农村居民点用地利用特征及其空间格局,是对农村居住与生产空间形态的直接反映,随着农村经济发展,农村土地越来越具有城镇用地的特征,因而在农村土地管理和规划上也必然要求有相应的改革和发展。研究结果可为土地规划、整治、农村产业发展和新型城镇化提供参考。     

Road-deposited sediment, soil and precipitation (RDS) in Bratislava, Slovakia: compositional and spatial assessment of contamination

Background, aim and scope  The urban environment in Bratislava is, in association with rapid urbanisation and industrialisation, significantly influenced by several potential sources of pollution, including automobile exhaust and industry emmissions. Urban road-deposited sediments contain many potentially toxic elements such as Pb, Cr, Cu, Zn and also Fe at concentrations much higher than in soil. In this study, the chemical composition and spatial variability of road-deposited sediments in urban area of Bratislava were assessed for the elements As, Cd, Cr, Cu, Hg, Ni, Pb, Fe and Mn. Additional evaluation of archive data for soil, snow and atmospheric dust was undertaken to provide an integrated view on urban environment contamination. Materials and methods  Urban road-deposited sediments (RDS) were collected during summer 2003 and 2004 mainly from major city crossroads. RDS samples were analysed for total metal content, pseudo-total metal content (HNO₃ digestion) and by a sequential extraction method, grain fraction composition and mineralogical composition (X-ray analysis). Metal concentrations in soil and snow samples from urban and non urban city area were compared. Results and discussion  The highest concentrations for all metals were found in the finest RDS fraction (<0.125 mm). Whilst in the fraction <1 mm mean concentrations of Cr, Cu and Pb reached 55.2, 143.8 and 34.4 mg kg⁻¹, respectively, for the fraction <0.125 mm, markedly higher contents of these elements were documented at the level of 86.8, 218.4 and 63.1 mg kg⁻¹, respectively. The soil contents of potentially toxic risk elements in the urban area including As, Cr, Cu, Fe, Hg, Mn, Ni, Pb and Zn were higher than in the non-urban area (except for Cd with similar contents). This distribution pattern of evaluated chemicals in urban and non-urban area is more evident in the case of winter precipitation (snow). The snow concentrations of As, Cr, Cu, Fe, Mn, Pb and Zn in the urban area were two tot five times higher than in non-urban area. Conclusions and recommendations  Monitoring of road-deposited sediments, dust, soil and precipitation has confirmed the significant contamination of the urban environment in Bratislava with potentially toxic elements that can pose a threat for the health of its residents. Future works should be based on analyses of temporal variability of RDS and analyses of organic matter content.     

Biochemical characterization of urban soil profiles from Stuttgart, Germany

The knowledge of biochemical properties of urban soils can help to understand nutrient cycling in urban areas and provide a database for urban soil management. Soil samples were taken from 10 soil profiles in the city of Stuttgart, Germany, differing in land use—from an essentially undisturbed garden area to highly disturbed high-density and railway areas. A variety of soil biotic (microbial biomass, enzyme activities) and abiotic properties (total organic C, elemental C, total N) were measured up to 1.9 m depth. Soil organic matter was frequently enriched in the subsoil. Microbial biomass in the top horizons ranged from 0.17 to 1.64 g C kg⁻¹, and from 0.01 to 0.30 g N kg⁻¹, respectively. The deepest soil horizon at 170-190 cm, however, contained 0.12 g C kg⁻¹ and 0.05 kg N kg⁻¹ in the microbial biomass. In general, arylsulphatase and urease activity decreased with depth but in three profiles potentially mineralizable N in the deepest horizons was higher than in soil layers directly overlying. In deeply modified urban soils, subsoil beside topsoil properties have to be included in the evaluation of soil quality. This knowledge is essential because consumption of natural soils for housing and traffic has to be reduced by promoting inner city densification.     

城市化进程中的土壤有机碳库演变趋势分析

土地利用方式变更引起的土壤碳库变化对全球温室效应、全球碳循环有重大的影响。基于1∶250000多目标地球化学调查数据,利用RS遥感影像和GIS统计技术,分析上海市的城市扩张格局及城市扩张进程中的土壤有机碳库演变趋势。根据上海地区1980、2000、2005年3期遥感影像分析,从1980年代开始,研究区城区面积快速扩张,城市生长以原市区为中心向周边扩展,1980~2005年间城市建设用地面积增加1 377 km2。研究区城区表层土壤有机碳分布呈现较大的空间变异性,城区表层土壤有机碳密度为(3.926±1.381)kg m-2,其均值是郊区的1.049倍,是乡村地区的1.255倍,随城市-郊区-乡村空间梯度演替,表层土壤有机碳密度渐趋降低,城区表层土壤呈现轻度积累;相较于第二次土壤普查农林生态系统,当前研究区城区表层土壤有机碳密度均值升高0.239 kg m-2,升幅6.48%。比较1980年前建城区、1980~2000年建城区、2000~2005年建城区与城市郊区土壤有机碳密度分布,新建城区由于土地利用方式变更强烈,土壤结构破坏,土壤有机碳密度基本上处于低值;随着城市用地年限的延长,城市生态系统的演化发展,土壤有机碳密度渐趋增大。研究提供城市化进程中的土壤有机碳库演变趋势信息,可为城市土壤固碳潜力研究提供数据支持,也为推动中国城市生态系统碳循环研究提供参考。     

Variability in topsoil texture and carbon content within soil map units and its implications in predicting soil water content for optimum workability

The ability to predict the timing of optimum soil workability depends on knowledge of the extent and structure of variability in main physical characteristics of the soil. Our objectives were to quantify the variability in texture and carbon content within soil map units in a small agriculture-dominated catchment in South-east Norway and to assess implications of variability in texture and carbon content on land management operations, using the predicted maximum water content for optimum workability as an example. Information from three different sources were used: a soil map (1:5000), a large sample grid (100 m spacing, 270 ha extent), and a small sample grid (10 m spacing, 2.25 ha extent). Readily available information on texture and organic matter content from the soil map was found to be of limited use for soil management due to broad textural classes together with deviations from the mapped main textural classes. There were significant differences in clay, silt and sand content between the different soil textural classes on the soil map. Statistical distributions within soil map units were generally either positively or negatively skewed and the coefficient of variation was intermediate, 15–50%. Most of the variation in both grids was spatially correlated. The large grid was dominated by a patchy structure, whilst the small grid showed a systematic trend with a gradual transition indicating fuzzy boundaries between map units in this catchment. The effective range for texture was 16 times larger in the large grid. Implications of variability in texture and carbon content on land management operations were assessed for the maximum water content for optimum workability (Wopt), predicted using pedotransfer functions. Wopt was usually in the same range as the water content at–100 kPa matric potential, indicating that considerable evaporation in addition to drainage is required for obtaining workable conditions in the field. The time required for obtaining the water content was estimated to about 5 days, which is longer than an average length of periods without precipitation in the area, median 3.7 days. Wopt predicted from the soil map deviated strongly from Wopt predicted from the sample grids. Comparing estimates of Wopt from the large grid with measurements in the small grid showed differences corresponding to ±2–3 days of evaporation.     

城市土壤压实对土壤水分特征的影响——以南京市为例

通过对南京市不同土地利用下的土壤容重、孔隙度和土壤水分特征曲线的测定，研究了压实对土壤水分特征参数的影响。结果表明城市土壤存在严重的压实退化现象，土壤容重和孔隙度能够很好地反映土壤的压实程度。随着压实程度的增加，土壤的田间持水量增加，萎蔫点含水量增加，而土壤的最大有效水含量却明显减少。所以，压实土壤对水分的调节能力下降，使其上生长的植物更不容易获得水分供应。