Quantifying trends and uncertainty in prehistoric forest composition in the upper Midwestern United States
Quantifying trends and uncertainty in prehistoric forest composition in the upper Midwestern United States
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DOI：
10.1002/ecy.2856
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发表时间：
2019-09-13
期刊：
影响因子：
4.8
通讯作者：
Williams, John W.
中科院分区：
文献类型：
--
作者：
Dawson, Andria;Paciorek, Christopher J.;Williams, John W.
北美东部的森林生态系统在过去的几千年里一直处于变化之中，远远早于欧美的土地清理和20世纪人类气候变化的开始。然而，史前植被变化的幅度和不确定性一直难以量化，因为多个生态，扩散和沉积过程，管理森林组成和化石花粉组合之间的关系。在这里，我们扩展STEPPS，贝叶斯层次时空花粉植被模型，估计在美国中西部地区的森林组成的变化，从大约2,100年到300年前。使用这种方法，我们发现一些物种的相对丰度发生了很大变化的证据，以及群落组成的显着变化。然而，这些变化是在区域变化的背景下发生的，这些变化的幅度很小或在统计上不显著，表明森林动态的时空格局很复杂。最大的变化是北方威斯康星州在过去2,000年中加拿大铁杉的填充。尽管范围填充，T. canadensis大致稳定，但向西略有扩张。在明尼苏达州和威斯康星州西北部，温带硬木林和北方硬木/针叶混交林之间的区域过渡带向西南移动了15-20公里。白蜡树、榆树和其他梅西奇硬木在明尼苏达州南部的大森林地区扩张。随着古生态数据网络密度的增加和统计建模方法的进步，现在可以自信地检测过去2,000年来森林组成的微妙但重要的变化。
Forest ecosystems in eastern North America have been in flux for the last several thousand years, well before Euro-American land clearance and the 20th-century onset of anthropogenic climate change. However, the magnitude and uncertainty of prehistoric vegetation change have been difficult to quantify because of the multiple ecological, dispersal, and sedimentary processes that govern the relationship between forest composition and fossil pollen assemblages. Here we extend STEPPS, a Bayesian hierarchical spatiotemporal pollen-vegetation model, to estimate changes in forest composition in the upper Midwestern United States from about 2,100 to 300 yr ago. Using this approach, we find evidence for large changes in the relative abundance of some species, and significant changes in community composition. However, these changes took place against a regional background of changes that were small in magnitude or not statistically significant, suggesting complexity in the spatiotemporal patterns of forest dynamics. The single largest change is the infilling of Tsuga canadensis in northern Wisconsin over the past 2,000 yr. Despite range infilling, the range limit of T. canadensis was largely stable, with modest expansion westward. The regional ecotone between temperate hardwood forests and northern mixed hardwood/conifer forests shifted southwestward by 15-20 km in Minnesota and northwestern Wisconsin. Fraxinus, Ulmus, and other mesic hardwoods expanded in the Big Woods region of southern Minnesota. The increasing density of paleoecological data networks and advances in statistical modeling approaches now enables the confident detection of subtle but significant changes in forest composition over the last 2,000 yr.