Canopy gas exchange and growth of white spruce near the Arctic treeline: confronting measurements with models along natural and experimental resource gradients

北极林线附近的树冠气体交换和白云杉的生长：用沿自然和实验资源梯度的模型进行测量

• 批准号: 0909155
• 负责人: Patrick Sullivan
• 金额: $ 51.24万
• 依托单位: University of Alaska Anchorage Campus
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-01 至 2012-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0909155&HistoricalAwards=false
• 关键词: Canopy; gas; exchange; growth; white

The position of the arctic treeline has important implications for surface energy budgets and carbon cycling in a changing climate. Modeling efforts suggest these effects are relevant on regional and global scales. Our understanding of the controls on tree growth at the arctic treeline has been developed using tree ring studies, which are necessarily correlative and not mechanistic in nature. These tree ring studies have identified both positive and negative radial growth responses to warming in the later half of the 20th century. Investigators have speculated that negative growth trends reflect an increasing importance of temperature-induced drought stress and that treeline advance may be expected in mesic and wet areas, but not in dry areas, with future climate warming. Recent work has revealed several important complexities that clearly show we have oversimplified the relationships between climate and tree growth at the arctic treeline. Detailed measurements of seasonal changes in tree physiology and growth in response to changes in resource availability are now required to take our understanding to the next level. This work will coordinate continuous measurements of white spruce canopy gas exchange with weekly measurements of branch gas exchange and leader, branch, radial and fine root growth in trees receiving factorial nutrient and water supplements along a gradient of parent material depth. Results of the study will, for the first time: resolve the seasonality of C uptake and water loss in treeline white spruce; compare the seasonality and magnitudes of growth in all major organs; articulate the consequences of changes in resource availability for white spruce gas exchange physiology and growth along a gradient where resource availability varies naturally; and identify a process-based model that accurately describes the relationships between climate and tree growth at the arctic treeline.

在不断变化的气候中，北极树线的位置对地表能源预算和碳循环具有重要影响。建模工作表明，这些影响在区域和全球范围内都是相关的。我们对北极树线树木生长控制的理解是通过年轮研究发展起来的，这些研究必然是相关的，而不是本质上的机械性的。这些树轮研究已经确定了20世纪下半叶径向生长对气候变暖的积极和消极反应。研究人员推测，负增长趋势反映了温度诱导的干旱胁迫的重要性日益增加，随着未来气候变暖，中湿性地区的树木线可能会提前，但干旱地区不会。最近的研究揭示了几个重要的复杂性，清楚地表明我们过度简化了北极树线上气候和树木生长之间的关系。现在需要对树木生理和生长的季节性变化进行详细的测量，以响应资源可获得性的变化，将我们的理解带到下一个水平。这项工作将协调连续测量白云杉树冠气体交换和每周测量树枝气体交换，以及沿母质深度的梯度接受因子营养和水分补充的树木的主根、分枝、径向和细根生长。这项研究的结果将首次：解决树线白云杉吸收碳和水分损失的季节性；比较所有主要器官生长的季节性和大小；阐明白云杉气体交换生理和生长沿资源可获得性自然变化的梯度变化的后果；并确定准确描述北极树线气候和树木生长之间关系的基于过程的模型。