Glob Chang Biol. 2014 Jan;20(1):251-64. doi: 10.1111/gcb.12382.
Tree species are predicted to track future climate by shifting their geographic distributions, but climate-mediated migrations are not apparent in a recent continental-scale analysis. To better understand the mechanisms of a possible migration lag, we analyzed relative recruitment patterns by comparing juvenile and adult tree abundances in climate space. One would expect relative recruitment to be higher in cold and dry climates as a result of tree migration with juveniles located further poleward than adults. Alternatively, relative recruitment could be higher in warm and wet climates as a result of higher tree population turnover with increased temperature and precipitation. Using the USDA Forest Service's Forest Inventory and Analysis data at regional scales, we jointly modeled juvenile and adult abundance distributions for 65 tree species in climate space of the eastern United States. We directly compared the optimal climate conditions for juveniles and adults, identified the climates where each species has high relative recruitment, and synthesized relative recruitment patterns across species. Results suggest that for 77% and 83% of the tree species, juveniles have higher optimal temperature and optimal precipitation, respectively, than adults. Across species, the relative recruitment pattern is dominated by relatively more abundant juveniles than adults in warm and wet climates. These different abundance-climate responses through life history are consistent with faster population turnover and inconsistent with the geographic trend of large-scale tree migration. Taken together, this juvenile-adult analysis suggests that tree species might respond to climate change by having faster turnover as dynamics accelerate with longer growing seasons and higher temperatures, before there is evidence of poleward migration at biogeographic scales.
树木物种预计将通过改变其地理分布来追踪未来的气候，但在最近的大陆范围内的分析中，气候介导的迁移并不明显。为了更好地理解可能的迁移滞后的机制，我们通过比较气候空间中幼树和成年树的丰度来分析相对繁殖模式。由于树木随幼树向极地迁移，人们预计寒冷和干燥气候中的相对繁殖率会更高。或者，由于温度和降水升高导致树木种群更替增加，温暖和潮湿气候中的相对繁殖率可能会更高。我们使用美国农业部林务局在区域尺度上的森林清查和分析数据，在东美国的气候空间中联合建模了 65 个树种的幼树和成年丰度分布。我们直接比较了幼树和成年的最佳气候条件，确定了每个物种在高相对繁殖率的气候下的位置，并综合了跨物种的相对繁殖模式。结果表明，对于 77%和 83%的树种，幼树的最佳温度和最佳降水分别高于成年树。在物种层面上，温暖和潮湿气候下的相对繁殖模式是幼树比成年树更丰富。这些通过生活史的不同丰度-气候响应与更快的种群更替一致，与大尺度树木迁移的地理趋势不一致。总的来说，这种幼树-成年分析表明，树木物种可能通过更快的更替来应对气候变化，因为随着生长季节的延长和温度的升高，动态加速，在生物地理尺度上有证据表明向极地迁移之前。
