Characteristics of Soil Resources in Relation to Soil Security in China
        张甘霖(中国科学院南京土壤研究所土壤与农业可持续发展国家重点实验室 南京 210008)
        王秋兵(沈阳农业大学土地与环境学院 沈阳 110866)
        soil resources;land use;soil security;soil management
        我国土壤资源丰富多样, 空间分异明显, 但宜耕地面积小, 总体质量不高;受人为活动强烈影响, 土地垦殖率高, 耕地后备资源有限。总体上, 土壤资源数量和质量均属严重制约型, 人地、人粮矛盾突出, 特别是近20 年来, 由于利用管理缺乏合理的布局和规划, 建设占用耕地使优质耕地减少过快;生态脆弱带土地退化势头没有遏止, 土壤污染有加剧趋势, 土壤安全形势日趋严峻。我国土壤资源基础调查工作基础薄弱, 土壤资源现状不清, 缺乏科学有效的土地资源评价方法和标准, 土壤资源管理相对粗放。需要加强土壤资源科学的基础研究, 深化土壤功能与安全的内涵, 更新我国土壤资源清单, 为多目标土地利用提供基础数据、模型和决策。
        Soils have multiple functions such as supporting biomass production, holding and purifying water, buffering and cleaning pollutants, storing carbon, and maintaining global biodiversity. Soil security refers to the status of soil capability in maintaining those functions. When secured, soils can provide full ecosystem services according to the functions, otherwise ecosystem services are compromised. China has abundant soil resources which are distributed contrastingly across the major eco-zones. However, the total arable land accounts for only ca. 10% of the entire territory and per capita is only one third arable land of the world average. In general, soil quality of arable land is low. Subject to hilly environment, long-term cultivation history, and rapid development during the last decades, potential unused arable land is very limited. Overall, China is limited by land resources in terms of both quantity and quality. Given the inherited low quality and irrational use of land resources, for instance, shift of grassland to cultivated land in semi-arid region, deforestation for slope land cultivation, irrational irrigation by expanding artificially oasis in arid environment, soil degradation such as wind and water erosion, as well as secondary salinization in fragile ecosystems are still occurring. On the other hand, urbanization and industrialization is shirking already rare arable land especially those of high quality agriculturall and surrounding urban areas. More of concern is the increasing contamination risk caused by mining and industrial activities across the country. Those threats have put shadow on soil security status of China and triggered concerns about food safety, surface and ground water quality, biodiversity and ultimately human health, as well as overall sustainability. Among many others, important reasons causing soil security problem include lack of rational planning and adequate legitimate controls. With focus on the function of biomass production and less attention to other eco-services such as carbon sequestration and biodiversity protection, regardless of physical capacity, cultivation of marginal lands to agricultural and had led to serious soil degradation. The Grain for Green Project started in late 20th century was a significant attempt to pay attention to eco-services rather than food production, which has reversed substantially soil degradation problem in many parts of the country by reducing soil erosion and restoration of ecosystem functions. Lack of detailed soil information, suitable methodology for precise soil function assessment has prevented effective land use planning. The trade-off of shifting land uses must be evaluated quantitatively so alternative land use systems can be developed. So far, the soil data that can cover entire country is mainly from the second national soil survey which was conducted in 30 years ago, so the spatial resolution and precision are low, not to say the data is already outdated. Experience learned from developed countries such as the United States where soil maps of detailed map scales down to 1/10,000 showed that soil data has supported land use management for many purposes. Among those soil data users, the most benefited are actually non-agricultural industries, which means soil functions other than biomass production are very much valued. We therefore call on basic researches on defining, quantifying soil functions in the context of pedosphere and its interfaces with other earth spheres, or more specifically in the context of Critical Zone, so ecosystem services can be evaluated thoroughly across administrative boundaries and spatial scales and more beneficial land use planning can be implemented. Based on that, national soil security status and evolution trend can be assessed. To support the above-mentioned soil function and soil security assessment, new investment in establishing precisesoil resource inventory is required. By taking advantage of new technology and methods, high-resolution soil maps, in addition to detailed soil pedon database, can be built in a relatively short time period. After all, soil assessment on whatever functions or security status, land use polices, etc., rely heavily on precise soil resource information.
张甘霖 中科院南京土壤所副所长, 研究员, 兼任土壤与农业可持续发展国家重点实验室常务副主任。国家杰出青年基金获得者, 入选"百千万"人才工程, 国家自然科学基金学科评审组专家。中国土壤学会常务理事, 国际土壤科学联合会土壤发生委员会主席(2010—2014), 全球数字土壤制图网络东亚中心负责人, FAO"政府间土壤专家小组"(ITPS)成员。获国家自然科学奖二等奖和省部级科技成果奖5项。Geoderma, Soil Use and Management, 《中国科学-地球科学》等杂志编委。E-mail: glzhang@issas.ac.cn.