Data from: Seed origin and warming constrain lodgepole pine recruitment, slowing the pace of population range shifts

Understanding how climate warming will affect the demographic rates of different ecotypes is critical to predicting shifts in species distributions. Here we present results from a common garden, climate change experiment in which we measured seedling recruitment of lodgepole pine, a widespread North American conifer that is also planted globally. Seeds from a low-elevation provenance had greater recruitment to their third year (by 323%) than seeds from a high-elevation provenance across sites within and above its native elevation range and across climate manipulations. Heating reduced (by 49%) recruitment to the third year of both low- and high-elevation seed sources across the elevation gradient, while watering alleviated some of the negative effects of heating (108% increase in watered plots). Demographic models based on recruitment data from the climate manipulations and long-term observations of adult populations revealed that heating could effectively halt modeled upslope range expansion except when combined with watering. Simulating fire and rapid post-fire forest recovery at lower elevations accelerated lodgepole pine expansion into the alpine, but did not alter final abundance rankings among climate scenarios. Regardless of climate scenario, greater recruitment of low-elevation seeds compensated for longer dispersal distances to treeline, assuming colonization was allowed to proceed over multiple centuries. Our results show that ecotypes from lower elevations within a species’ range could enhance recruitment and facilitate upslope range shifts with climate change.

明晰气候变暖如何影响不同生态型（ecotype）的种群动态速率，对于预测物种分布范围的变化至关重要。本研究报道了一项同质园（common garden）气候变化实验的研究结果，实验中我们测定了扭叶松（lodgepole pine）的幼苗补充情况——这是一种在北美广泛分布且全球范围内均有引种的针叶树种。在该树种原生海拔范围内及以上的所有样地中，且无论采用何种气候调控处理，低海拔种源种子的第三年幼苗补充率均比高海拔种源种子高323%。在整个海拔梯度上，增温处理使低、高海拔种源种子的第三年幼苗补充率均降低了49%；而补水处理则缓解了部分增温带来的负面影响，补水样地的幼苗补充率提升了108%。基于气候调控实验的幼苗补充数据以及成年种群长期观测数据构建的种群动态模型显示，除非配合补水处理，否则增温将有效阻止模型预测的上坡位分布范围扩张。模拟低海拔区域的火灾及火灾后快速森林恢复过程，会加速扭叶松向高山地带的扩张，但并未改变不同气候情景下的最终种群丰度排序。无论采取何种气候情景，假设定植过程可延续多个世纪，低海拔种源种子更高的幼苗补充率可抵消其向树线（treeline）扩散所需的更长传播距离带来的不利影响。本研究结果表明，物种分布范围内低海拔区域的生态型，可通过提升幼苗补充能力，助力种群在气候变化背景下向上坡位实现分布范围迁移。