Homogenization of northern U.S. Great Lakes forests due to land use
Homogenization of northern U.S. Great Lakes forests due to land use
复制标题
由于土地利用导致美国五大湖北部森林均质化
作者：
L. Schulte;D. Mladenoff;T. Crow;L. Merrick;D. Cleland
近几十年来，人类对森林地区的土地利用不断加剧，威胁到长期可持续性。主要影响包括土地覆盖的转变或恢复到演替发展的早期阶段。这两种类型的变化都可以通过生态系统产生连锁效应；然而，人们对允许森林再生的长期影响知之甚少。我们结合历史公共土地调查记录和当前的森林清查和土地覆盖数据，量化了美国北部五大湖地区一个世纪以来欧美土地利用的区域规模后果。我们的分析显示了植被变化的独特而快速的轨迹，向历史上前所未有的简化条件发展。除了林地总体丧失之外，与欧美前的森林相比，目前的森林还具有物种多样性、功能多样性和结构复杂性较低的特点。当今森林的特点是阔叶落叶树种占主导地位——与欧美时期相比，构成该地区的所有 55 个生态区的针叶树相对优势地位较低。白杨（Populus grandidentata 和 P. tremuloides）和枫树（Acer saccharum 和 A. rubrum）构成了已取代针叶树的主要落叶树种。这些变化反映了该地区当地森林变化的累积效应，并影响未来的生态系统条件及其提供的生态系统服务。
Human land use of forested regions has intensified worldwide in recent decades, threatening long-term sustainability. Primary effects include conversion of land cover or reversion to an earlier stage of successional development. Both types of change can have cascading effects through ecosystems; however, the long-term effects where forests are allowed to regrow are poorly understood. We quantify the regional-scale consequences of a century of Euro-American land use in the northern U.S. Great Lakes region using a combination of historical Public Land Survey records and current forest inventory and land cover data. Our analysis shows a distinct and rapid trajectory of vegetation change toward historically unprecedented and simplified conditions. In addition to overall loss of forestland, current forests are marked by lower species diversity, functional diversity, and structural complexity compared to pre-Euro-American forests. Today’s forest is marked by dominance of broadleaf deciduous species—all 55 ecoregions that comprise the region exhibit a lower relative dominance of conifers in comparison to the pre-Euro-American period. Aspen (Populus grandidentata and P. tremuloides) and maple (Acer saccharum and A. rubrum) species comprise the primary deciduous species that have replaced conifers. These changes reflect the cumulative effects of local forest alterations over the region and they affect future ecosystem conditions as well as the ecosystem services they provide.