DataSheet_1_Forest types outpaced tree species in centroid-based range shifts under global change.pdf

IntroductionMounting evidence suggests that geographic ranges of tree species worldwide are shifting under global environmental changes. Little is known, however, about if and how these species’ range shifts may trigger the range shifts of various types of forests. Markowitz’s portfolio theory of investment and its broad application in ecology suggest that the range shift of a forest type could differ substantially from the range shifts of its constituent tree species.MethodsHere, we tested this hypothesis by comparing the range shifts of forest types and the mean of their constituent species between 1970–1999 and 2000–2019 across Alaska, Canada, and the contiguous United States using continent-wide forest inventory data. We first identified forest types in each period using autoencoder neural networks and K-means cluster analysis. For each of the 43 forest types that were identified in both periods, we systematically compared historical range shifts of the forest type and the mean of its constituent tree species based on the geographic centroids of interpolated distribution maps.ResultsWe found that forest types shifted at 86.5 km·decade-1 on average, more than three times as fast as the average of constituent tree species (28.8 km·decade-1). We showed that a predominantly positive covariance of the species range and the change of species relative abundance triggers this marked difference.DiscussionOur findings provide an important scientific basis for adaptive forest management and conservation, which primarily depend on individual species assessment, in mitigating the impacts of rapid forest transformation under climate change.

日益累积的证据表明，在全球环境变化的背景下，全球范围内树木物种的地理分布范围正在发生变迁。然而，关于这些物种分布范围的变迁是否以及如何可能引发各种类型森林分布范围的变迁，目前所知甚少。马尔科夫投资组合理论及其在生态学中的广泛应用提示，森林类型的分布变迁可能与构成其基础的树木物种的分布变迁存在显著差异。研究方法在本研究中，我们通过比较阿拉斯加、加拿大和北美大陆的森林类型及其构成物种在1970-1999年和2000-2019年间的分布变迁，来检验上述假设。我们首先利用自编码器神经网络和K-means聚类分析识别出每个时期的森林类型。对于在两个时期均被识别的43种森林类型，我们基于插值分布图的地理解析中心，系统地比较了森林类型的历史分布变迁及其构成物种的平均分布变迁。研究结果我们发现，森林类型的平均分布变迁速度为86.5公里/十年，是构成物种平均分布变迁速度（28.8公里/十年）的三倍以上。我们证明了物种分布范围与物种相对丰度变化之间的正相关协方差是导致这种显著差异的主要原因。讨论我们的研究结果为适应性的森林管理和保护提供了重要的科学依据，这主要依赖于对单个物种的评估，有助于缓解气候变化下快速森林转型带来的影响。