Climate change is projected to cause extensive plant range shifts, and, in many cases such shifts already are underway. Most long‐term studies of range shifts measure emergent changes in species distributions but not the underlying demographic patterns that shape them. To better understand species' elevational range shifts and their underlying demographic processes, we use the powerful approach of rephotography, comparing historical (1978–1982) and modern (2015–2016) photographs taken along a 1000‐m elevational gradient in the Colorado Desert of Southern California. This approach allowed us to track demographic outcomes for 4263 individual plants of 11 long‐lived, perennial species over the past ~36 years. All species showed an upward shift in mean elevation (average = 45 m), consistent with observed increasing temperature and severe drought in the region. We found that varying demographic processes underlaid these elevational shifts, with some species showing higher recruitment and some showing higher survival with increasing elevation. Species with faster life‐history rates (higher background recruitment and mortality rates) underwent larger elevational shifts. Our findings emphasize the importance of demography and life history in shaping range shift responses and future community composition, as well as the sensitivity of desert systems to climate change despite the typical “slow motion” population dynamics of perennial desert plants.

中文翻译：

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对比鲜明的人口过程是沙漠生态系统中艰难变化的基础


预计气候变化将导致植物范围的广泛变化，而且在许多情况下，这种变化已经在进行中。大多数关于范围变化的长期研究测量的是物种分布的紧急变化，而不是塑造它们的潜在人口模式。为了更好地了解物种的海拔范围变化及其潜在的人口统计过程，我们使用了强大的重摄影方法，比较了在南加州科罗拉多沙漠沿 1000 m 海拔梯度拍摄的历史 （1978-1982） 和现代 （2015-2016） 照片。这种方法使我们能够跟踪过去 ~36 年中 11 种长寿多年生物种的 4263 株单株植物的种群统计结果。所有物种的平均海拔均呈上升趋势（平均 = 45 m），这与该地区观察到的温度升高和严重干旱一致。我们发现，不同的种群过程是这些海拔变化的基础，一些物种表现出更高的补充，而另一些物种则随着海拔的增加而表现出更高的存活率。生活史速率较快的物种 （较高的背景补充和死亡率） 经历了更大的海拔偏移。我们的研究结果强调了人口统计学和生活史在塑造范围变化响应和未来群落组成方面的重要性，以及沙漠系统对气候变化的敏感性，尽管多年生沙漠植物具有典型的“慢动作”种群动态。