A new perspective on Quaternary land cover in central Alaska
A new perspective on Quaternary land cover in central Alaska
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2017-09
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通讯作者：
E. Hopla
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作者：
E. Hopla
在北方高纬度地区，植被已经对全球气温的上升做出了反应，灌木向极地扩展，这一过程被称为“绿化”。鉴于全球气温上升，过去气候驱动的植被变化可用作未来变暖情景的类比。这项研究解决了阿拉斯加在整个晚冰期和全新世的植被变化，特别是如何在目前的重建植被组成的准确性可以提高。景观重建算法（LRA，Sugita 2007 a，B）是一个两步框架，用于在各种空间尺度上定量重建土地覆盖。该模型REVEALS估计区域植被丰富度从花粉记录从大湖泊，然后被纳入模型LOVE到达当地的植被估计（使用花粉记录从小湖泊）。花粉生产力估计（PPE）是LRA中使用的主要参数之一。在这项研究中提出的第一个花粉生产力的估计占主导地位的森林和苔原类群在阿拉斯加内陆。高、低花粉生产者的分类学排名与欧洲相当。PPE与REVEALS模型一起使用，以获得阿拉斯加中北部区域植被的定量重建。然后在南布鲁克斯山脉的两个小湖鲁珀特湖和3号湖的景观中评估了上帝抵抗军方法的有效性。结果表明，在阿拉斯加州的小湖泊产生相同的花粉信号的大型湖泊和启示提供了类似的结果，因为当地的植被是非常相似的区域平均植被的爱情。从REVEALS的应用中产生了几个关键的见解和前景：i）在冰川晚期扩张之后，桦木可能不像以前认为的那样占优势，而是与柳共同占优势; ii）落叶，杨树林可能在全新世早期广泛存在;和iii）阿拉斯加的LRA需要在有3个小湖和1个大湖的苔原上进行进一步的测试和验证，并将提供进一步评估新阿拉斯加PPE可靠性的机会。
In the high northern latitudes vegetation is already responding to increasing global temperatures, with shrubs expanding poleward in a process called “greening”. In light of increasing global temperatures, past climate-driven shifts in vegetation can be used as analogues for future warming scenarios. This study addresses vegetation change in Alaska throughout the late glacial and Holocene, specifically how the accuracy of vegetation composition can be improved over current reconstructions. The Landscape Reconstruction Algorithm (LRA, Sugita 2007a, b) is a two-step framework for quantitative reconstruction of land cover across various spatial scales. The model REVEALS estimates regional vegetation abundance from pollen records from large lakes, which is then incorporated into the model LOVE to arrive at local estimates of vegetation (using pollen records from small lakes). Pollen productivity estimates (PPEs) are one of the major parameters used in the LRA. The first pollen productivity estimates for the dominant forest and tundra taxa in Interior Alaska are presented in this study. The taxonomic ranking of high and low pollen producers are comparable with Europe. PPEs were used with the REVEALS model to obtain quantitative reconstructions of regional vegetation in north-central Alaska. The effectiveness of the LRA approach was then assessed in the landscape of the south Brooks Range at two small lakes, Ruppert and Lake 3. Results indicate that small lakes in Alaska produce the same pollen signal as large lakes and that REVEALS provides similar results as LOVE as the local vegetation is very similar to the regional mean vegetation. Several key insights and prospects arise from the application of REVEALS: i) after its late glacial expansion, Betula may not have been as dominant as previously thought, but rather co-dominant with Salix; ii) deciduous, Populus woodland may have been extensive in the early Holocene; and iii) The LRA in Alaska needs further testing and validation in the tundra with 3 small lakes and 1 large lake, and would provide an opportunity to further assess the reliability of the new Alaskan PPEs.