Reproduction as a bottleneck to treeline advance across the circumarctic forest tundra ecotone

The fundamental niche of many species is shifting with climate change, especially in sub-arctic ecosystems with pronounced recent warming. Ongoing warming in sub-arctic regions should lessen environmental constraints on tree growth and reproduction, leading to increased success of trees colonising tundra. Nevertheless, variable responses of treeline ecotones have been documented in association with warming temperatures. One explanation for time lags between increasingly favourable environmental conditions and treeline ecotone movement is reproductive limitations caused by low seed availability. Our objective was to assess the reproductive constraints of the dominant tree species at the treeline ecotone in the circumpolar north. We sampled reproductive structures of trees (cones and catkins) and stand attributes across circumarctic treeline ecotones. We used generalized linear mixed models to estimate the sensitivity of seed production and the availability of viable seed to regional clim...

许多物种的基础生态位（fundamental niche）正随气候变化发生偏移，尤其是在近年来升温显著的亚北极生态系统中。亚北极区域持续升温本应缓解林木生长与繁殖所受的环境限制，提升林木在苔原的定植成功率。然而，已有研究记录到林线交错带（treeline ecotone）对升温存在各异的响应。环境条件愈发适宜却未能推动林线交错带迁移，其间存在的时间滞后现象，其中一种解释是种子供给不足引发的繁殖限制。本研究旨在评估环北极北部林线交错带优势树种所面临的繁殖限制。我们对环北极林线交错带内的林木繁殖结构（球果与柔荑花序）以及林分特征开展了采样。我们采用广义线性混合模型（generalized linear mixed models），估算种子产出与有活力种子供给对区域气候...的敏感性。