Coordination of the Research Unit and development of a conceptual model of paddy soil evolution

水稻土可能起源于许多不同类型的土壤，但受人类活动的高度改造。它们大多是在水下条件下管理的，就元素循环而言，导致了独特的农业生态系统。然而，气候变化和来自其他部门的竞争将严重影响水稻种植的水资源供应。因此，由两个DFG研究单位组织的联合国际研讨会专注于水稻生产和相关的水稻土壤发展，旨在更深入地了解不同管理制度下C和N平衡的过程。DFG研究单位995(稻田土壤演变的生物地球化学)专注于鉴定导致稻田土壤演变的土壤形成过程。为了理解水稻土的演化，我们必须考虑水文和微生物介导的氧化还原过程对土壤矿物和土壤有机质动态的影响。这与有机碳(OC)和氮(N)以及铁(Fe)的微生物可获得性问题密切相关。不同的初始自然条件可能需要不同的水稻栽培管理措施，这可能决定水稻土壤演变的方向。水稻土和非淹水农业土的直接比较可以识别和量化不同类型土壤中由管理引起的生物地球化学性质的差异。这些调查与DFG研究单元1701(在以水稻为主的景观中引入非淹水作物：对碳、氮和水循环的影响，ICON)密切相关。这个研究单位探索并量化了水稻为主的景观中作物多样化的生态后果。从每年两种淹水的水稻作物转向与一种或两种非淹水的作物轮作，如玉米或非淹水(旱作)水稻，在水文、元素循环和生态系统功能方面会产生明显的影响。与水稻/玉米轮作相比，水稻/水稻轮作中较高的有机碳含量只能部分补偿较高的甲烷(CH4)排放。非水淹作物减少的CH4排放至少部分被N2O排放的增加(污染交换)所抵消。解决这些方面的跨学科问题将有助于理解和量化未来水稻生态系统中碳、氮和水的短期和长期动态。因此，整合这两个研究单位的成果和知识，以及与具有水稻生产专业知识的国际科学家交流经验，将大大有助于深化我们对水稻土壤中依赖管理的生物地球化学过程的见解。

Paddy soils may originate from many different types of soil but are highly modified by human activities. They are mostly managed under submerged conditions, leading to a unique agroecosystem in terms of element cycling. However, climate change and competition from other sectors will severely affect water availability for rice cropping. Thus, a joint international workshop, organised by two DFG Research Units focussing on paddy rice production and associated paddy soil development aims at gaining more insight into processes of C and N balances due to different management systems. The DFG Research Unit 995 (Biogeochemistry of Paddy Soil Evolution) focusses on the identification of soil forming processes responsible for paddy soil evolution. To understand paddy soil evolution, we have to consider the dynamics of hydrologically and microbially mediated redox processes to the dynamics of soil minerals and soil organic matter. This is strongly related to the question of the microbial accessibility of organic carbon (OC) and nitrogen (N), but also of iron (Fe). Different initial natural conditions may require different management practices for rice cultivation, and these may determine the direction of paddy soil evolution. The direct comparison of paddy soils and non-flooded agricultural soils allows to identify and to quantify management induced differences of biogeochemical properties in different soil types. These investigations are strongly related to the DFG Research Unit 1701 (Introducing Non-Flooded Crops in Rice Dominated Landscapes: Impact on Carbon, Nitrogen and Water Cycles, ICON). This Research Unit explores and quantifies the ecological consequences of crop diversification in rice dominated landscapes. Diversion from two flooded rice crops per year to rotations with one or two non-flooded crops, such as maize or non-flooded (aerobic) rice, entails pronounced implications in terms of hydrology, element cycling and ecosystem functioning. The higher OC content in rice/rice rotations as compared to rice/maize rotations only partially compensates for higher methane (CH4) emissions. Reduced CH4 emissions in non-flooded crops are at least in part offset by increased N2O emissions (pollution swapping). Addressing these aspects trans-disciplinary will help understanding and quantifying the short and long term dynamics of carbon, nitrogen and water in up-coming rice ecosystems. Thus, integrating the results and knowledge of both Research Units as well as the exchange of experiences with international scientists with professional expertise on paddy rice production will contribute greatly to deepen our insights concerning management-depending biogeochemical processes in paddy soils.