Nutrient release from coniferous woodland stimulated by changes in forest management: A new nitrate time bomb?

森林管理变化刺激针叶林释放养分：新的硝酸盐定时炸弹？

• 批准号: 2284192
• 金额: --
• 依托单位: University of Reading
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2019
• 资助国家: 英国
• 起止时间: 2019 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2284192
• 关键词: Nutrient; release; coniferous; woodland; stimulated

Despite large UK reductions in nitrogen (N) emissions since 1970, recent total N deposition was unchanged. Nutrient models indicate that N loads in most broadleaf and conifer systems in the UK exceed critical limits. Forest ecosystems are efficient atmospheric nitrogen scavengers and can accumulate more nitrogen than other land uses, particularly near woodland edges and where habitat fragmentation has occurred. Data collected by Forest Research suggest that large amounts of nitrogen and carbon (C) have accumulated in forest soils and in particular in the upper organic soil horizons. Increased leaching of N and C species has been detected at a number of sites. Nitrogen stored in forest soils presents a risk to water quality if N stores are mineralized and released as a result of changes in forest management. Nitrogen losses to aquatic systems cost billions of pounds per year globally in water treatment and environmental damage from eutrophication. Despite this risk, the potential impact of changes in forest management on N leaching from forests to aquatic systems is poorly understood. Current government policy proposes more afforestation, but also changes to tree species which are more suitable for future climates, and converting some conifer systems to native broadleaves. In addition, productive forests are associated with intensive forest management processes which all can disturb the soils before tree planting, during forest development and harvest. Changes in forest due to pests and diseases could also have profound impact on nitrate inputs and leaching in forest ecosystems. In summary, we are expecting significant change of forest cover which is likely to alter established N leaching regimes which we know little about, thus creating a major research need.ApproachThis PhD will quantify the impacts of changes in forest management practices on nitrogen fate and transport beneath forested areas in the UK. The PhD will use monitoring and modelling approaches to quantify N fluxes to aquatic systems at a range of scales. The PhD will achieve this through the following tasks:1. Detailed quantitative analysis of long term (>15 years) monitoring data of soil and soil solution nitrogen (total, nitrate, ammonium, dissolved organic nitrogen) measured at 10 Forest Research monitoring sites across the UK. Additional monitoring data collection and lab analysis will be carried out (soil N leaching, groundwater nitrate concentrations, pore water profiles).2. Development of conceptual and process-based models of N leaching to aquatic systems parameterised at each site, and a number of generalised scenarios describing N leaching from forests, to be used in large scale modelling.3. Upscaling of site-specific models to national scale by exploiting national scale datasets from Forest Research and CEH, e.g. BioSoil (220 sites) and soil survey and hydrogeological data.4. Application of developed models (site and national scales) to predict impacts of changes in forest management on N fluxes from forests, and resultant impacts on aquatic system N concentrations.

尽管自 1970 年以来英国氮 (N) 排放量大幅减少，但近期氮沉降总量没有变化。营养模型表明，英国大多数阔叶树和针叶树系统中的氮负荷超过了临界限值。森林生态系统是有效的大气氮清除剂，可以比其他土地利用积累更多的氮，特别是在林地边缘附近和发生栖息地破碎化的地方。森林研究收集的数据表明，森林土壤中，特别是上层有机土壤层中积累了大量的氮和碳（C）。在许多地点都检测到氮和碳的淋滤增加。如果由于森林管理的变化而矿化并释放储存在森林土壤中的氮，则储存在森林土壤中的氮会对水质造成风险。全球水生系统的氮损失每年在水处理和富营养化造成的环境破坏方面造成数十亿英镑的损失。尽管存在这种风险，但人们对森林管理变化对氮从森林淋滤到水生系统的潜在影响知之甚少。目前的政府政策建议更多造林，但也改变了更适合未来气候的树种，并将一些针叶树系统转变为本土阔叶树。此外，生产性森林与集约化森林管理过程相关，这些过程都会在植树前、森林开发和采伐过程中扰动土壤。病虫害引起的森林变化也可能对森林生态系统中的硝酸盐输入和淋溶产生深远影响。总之，我们预计森林覆盖将发生重大变化，这可能会改变我们知之甚少的既定氮淋滤机制，从而产生重大研究需求。方法本博士将量化森林管理实践变化对英国森林地区氮归宿和运输的影响。该博士将使用监测和建模方法来量化一定范围内水生系统的氮通量。博士将通过以下任务来实现这一目标：1。对英国 10 个森林研究监测点测量的土壤和土壤溶液氮（总氮、硝酸盐、铵、溶解有机氮）的长期（>15 年）监测数据进行详细的定量分析。将进行额外的监测数据收集和实验室分析（土壤氮淋滤、地下水硝酸盐浓度、孔隙水剖面）。2．开发在每个地点参数化的水生系统氮淋滤概念和基于过程的模型，以及描述森林氮淋滤的一些通用场景，用于大规模建模。3．通过利用森林研究和 CEH 的国家规模数据集，将特定地点模型升级到国家规模，例如生物土壤（220个点）和土壤调查和水文地质数据。4．应用已开发的模型（地点和国家尺度）来预测森林管理变化对森林氮通量的影响，以及对水生系统氮浓度的影响。