Riparian shrub expansion: Linkages to permafrost, hydrology and soil microbes

河岸灌木扩张：与永久冻土、水文学和土壤微生物的联系

• 批准号: 1630360
• 负责人: Anna Liljedahl
• 金额: $ 6.19万
• 依托单位: University of Alaska Fairbanks Campus
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-07-01 至 2017-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1630360&HistoricalAwards=false
• 关键词: Riparian; shrub; expansion; Linkages; permafrost

The climatic drivers and landscape-scale patterns of recent Arctic shrub expansion are well understood, while the biogeochemical and physical mechanisms controlling shrub recruitment and growth remain unclear. The biogeophysical characteristics associated with tall shrub expansion near streams could potentially explain the documented increases in carbon and nutrient export from large Arctic rivers through the underlying processes of widespread permafrost degradation and increased subsurface flow. Additionally, occurrences of tall shrubs could be used as a readily measured proxy for subsurface properties both across space and time using remote sensing. If our observations hold true in other stream environments, the information has the potential to provide novel hydrological, permafrost, and biological process insights to complement the extensive literature on increasing Arctic shrub cover. Preliminary measurements of differential runoff in Arctic tundra link tall shrubs along riparian corridors to losing stream sections (streams with decreasing discharge downstream), whereas gaining or maintaining stream sections (increasing discharge downstream) lack tall shrubs.This award will support measurements to test whether the formation of a talik (permafrost-free ground) and a downward hydrologic gradient creates a biogeochemical subsurface environment that favors shrub recruitment and growth, which, in turn, results in patterns of tall shrub distribution coinciding along losing stream reaches. This team will measure additional streams with differing gradients, bed morphologies, and substrates to test the statistical significance of their preliminary observation that tall shrubs indicate losing streams, and to expand measurements to include shrub height, cover, biomass, Leaf Area Index (LAI), permafrost, and soil microbial communities. The award will support three early career researchers to gather background data to enable them to explore a potentially transformative idea to set the foundation to examine the processes linking shrubs, permafrost, hydrology and microbiology. The results of this work would be disseminated directly to land management and private organizations.

最近北极灌木扩展的气候驱动因素和景观尺度模式已被很好地了解，而控制灌木招募和生长的生物地球化学和物理机制仍不清楚。与溪流附近高大灌木扩张有关的生物地球物理特征可能解释北极大型河流通过广泛的永久冻土退化和地下水流增加的潜在过程而增加的碳和养分输出。此外，高大灌木的出现可以很容易地作为利用遥感跨空间和跨时间测量地下特性的指标。如果我们的观察在其他河流环境中成立，这些信息有可能提供新的水文、永久冻土和生物过程洞察，以补充关于北极灌木覆盖率增加的广泛文献。北极冻土带差异径流的初步测量将沿河岸走廊的高大灌木连接到失去的溪流段(下游流量减少的溪流)，而获得或保持溪流段(增加下游的流量)缺乏高大灌木。该奖项将支持测试是否形成塔里克(无冻土层)和向下的水文梯度是否创造了有利于灌木补充和生长的生物地球化学地下环境，这反过来又导致沿着失去的溪流段的高大灌木分布模式重合。该团队将测量具有不同坡度、床形态和基质的额外溪流，以测试他们初步观察到的高灌木表明溪流减少的统计意义，并扩大测量范围，包括灌木高度、盖度、生物量、叶面积指数(LAI)、永久冻土和土壤微生物群落。该奖项将支持三名职业早期研究人员收集背景数据，使他们能够探索一种潜在的变革性想法，为研究灌木、永久冻土、水文学和微生物学之间的联系奠定基础。这项工作的成果将直接分发给土地管理和私营组织。