Global Change and the Carbon Balance of Arctic Ecosystems: The Importance of Carbon-Nutrient Interactions in Soils

全球变化和北极生态系统的碳平衡：土壤中碳-养分相互作用的重要性

• 批准号: 9615563
• 负责人: Knute Nadelhoffer
• 金额: $ 74.28万
• 依托单位: Marine Biological Laboratory
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-04-01 至 2001-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9615563&HistoricalAwards=false
• 关键词: Global; Change; Carbon; Balance; Arctic

9615563 Nadelhoffer Changes in terrestrial carbon cycles are often tightly constrained by interactions between C and other elements, especially N and P. The aim of this research is to improve the understanding of how carbon/nutrient interactions in soils might affect the responses of arctic tundra ecosystems to global environmental change. The research centers on the question, "What controls the amount of C lost from tundra soils per unit N made available for plant uptake?" This question is important because plant C gain in tundra ecosystems is often strongly N-limited, and virtually all of the N made available to vascular plants in tundra ecosystems comes from microbial mineralization of soil organic matter. Thus the overall C balance of the ecosystem is largely determined by the balance of plant C gains associated with N uptake versus C losses due to soil respiration. The design of the research is guided by a simple conceptual model, in which the large amount of soil organic matter in tundra ecosystems is viewed as being composed of three interacting organic matter pools with different turnover times and characteristic C:N ratios (microbes are a fourth pool that mediates turnover of the other three, but which is also much smaller than the other three). The overall hypothesis is that the balance of C lost: N made available in tundra soils is controlled by interactions between the chemical quality of soil organic matter (including fresh litter) and environmental factors that determine the relative rates of decomposition and interconversion of the various organic matter pools. Additional hypotheses deal with the individual effects of (1) soil organic matter quality, (2) drainage and associated aerobic/anaerobic conditions, and (3) temperature. These hypotheses will be tested by measuring C losses and N made available in soils from contrasting tundra ecosystem types that are already known to differ in initial organic matter quality. A field experiment will compare wet, moist, and dry heath tundras, and two laboratory experiments will compare wet and moist tundras. One laboratory experiment will be on whole plant-soil monoliths transported from the field, and the other laboratory experiment will be on soils only; treatments will include manipulations of temperature, drainage, and N and P availability. Isotopic tracers and natural abundances of C & N isotopes in various soil organic matter fractions will be used to help estimate interactions and turnover rates of the major organic matter pools. Because the experiments are long-term (the laboratory experiment will simulate 4 full growing seasons over the 3 years of the research, and the field measurements will be made in the 10th through the 12th years of an experiment begun in 1988), it may be possible to document changes in characteristics of organic matter pools themselves, as well as the fluxes into and out of them. In addition to direct tests of the hypotheses with data, a simulation model (MBL-GEM) will be used as a synthesis tool and for longer-term prediction and integration with past research on vegetation C-N interactions.

9615563 Nadelhoffer 陆地碳循环的变化通常受到 C 和其他元素（尤其是 N 和 P）之间相互作用的严格限制。这项研究的目的是提高对土壤中碳/养分相互作用如何影响北极苔原生态系统响应的理解到全球环境变化。该研究的中心问题是“什么控制着植物吸收的每单位​​氮从苔原土壤中流失的碳量？”这个问题很重要，因为苔原生态系统中植物碳的获取通常受到氮的强烈限制，而且苔原生态系统中维管植物获得的几乎所有氮都来自土壤有机质的微生物矿化。因此，生态系统的总体碳平衡很大程度上取决于植物与氮吸收相关的碳增益与土壤呼吸导致的碳损失之间的平衡。 该研究的设计以一个简单的概念模型为指导，其中苔原生态系统中的大量土壤有机质被视为由三个相互作用的有机质库组成，这些有机质库具有不同的周转时间和特征碳氮比（微生物是第四个池调节其他三个池的营业额，但也比其他三个池小得多）。总体假设是，苔原土壤中的碳平衡：氮的平衡是由土壤有机质（包括新鲜枯枝落叶）的化学质量与环境因素之间的相互作用控制的，环境因素决定了各种有机物分解和相互转化的相对速率。物质池。其他假设涉及以下因素的个体影响：(1) 土壤有机质质量，(2) 排水和相关的有氧/厌氧条件，以及 (3) 温度。 这些假设将通过测量对比苔原生态系统类型土壤中的碳损失和可用氮来检验，这些生态系统类型已知初始有机质质量不同。现场实验将比较潮湿、潮湿和干燥的石南苔原，两个实验室实验将比较潮湿和潮湿的苔原。一项实验室实验将在从田间运来的整个植物-土壤巨石上进行，另一项实验室实验将仅在土壤上进行；处理方法包括控制温度、排水以及氮和磷的有效性。同位素示踪剂和各种土壤有机质组分中 C 和 N 同位素的自然丰度将用于帮助估计主要有机质库的相互作用和周转率。由于实验是长期的（实验室实验将在研究的 3 年中模拟 4 个完整的生长季节，而现场测量将在 1988 年开始的实验的第 10 到第 12 年进行），因此可能可以记录有机物池本身特征的变化，以及进出有机物池的通量。除了用数据直接测试假设外，模拟模型（MBL-GEM）将用作综合工具，用于长期预测以及与过去植被碳氮相互作用研究的整合。