Data from: Limited alpine climatic warming and modeled phenology advancement for three alpine species in the Northeast United States

Premise of the study: Most alpine plants in the Northeast United States are perennial and flower early in the growing season, extending their limited growing season. Concurrently, they risk the loss of reproductive efforts to late frosts. Quantifying long-term trends in northeastern alpine flower phenology and late-spring/early-summer frost risk is limited by a dearth of phenology and climate data, except for Mount Washington, New Hampshire (1916 m a.s.l.). Methods: Logistic phenology models for three northeastern US alpine species (Diapensia lapponica, Carex bigelowii and Vaccinium vitis-idaea) were developed from 4 yr (2008–2011) of phenology and air temperature measurements from 12 plots proximate to Mount Washington’s long-term summit meteorological station. Plot-level air temperature, the logistic phenology models, and Mount Washington’s climate data were used to hindcast model yearly (1935–2011) floral phenology and frost damage risk for the focal species. Key results: Day of year and air growing degree-days with threshold temperatures of −4°C (D. lapponica and C. bigelowii) and −2°C (V. vitis-idaea) best predicted flowering. Modeled historic flowering dates trended significantly earlier but the 77-yr change was small (1.2–2.1 d) and did not significantly increase early-flowering risk from late-spring/early-summer frost damage. Conclusions: Modeled trends in phenological advancement and sensitivity for three northeastern alpine species are less pronounced compared with lower elevations in the region, and this small shift in flower timing did not increase risk of frost damage. Potential reasons for limited earlier phenological advancement at higher elevations include a slower warming trend and increased cloud exposure with elevation and/or inadequate chilling requirements.研究背景：美国东北部多数高山植物为多年生类群，且于生长季早期开花以延长其有限的生长季；但与此同时，它们面临晚霜导致生殖投入损失的风险。目前，除海拔1916米的新罕布什尔州华盛顿山外，由于物候与气候数据匮乏，针对该区域高山植物开花物候及春末/夏初霜害风险的长期趋势量化研究受到极大限制。 方法：基于华盛顿山长期山顶气象站周边12个样地2008至2011年共4年的物候与气温观测数据，构建了美国东北部3种高山植物——岩梅（Diapensia lapponica）、比格洛薹草（Carex bigelowii）及越橘（Vaccinium vitis-idaea）的逻辑斯蒂物候模型。随后结合样地尺度气温数据、上述物候模型及华盛顿山气候数据集，对1935至2011年期间目标物种的年际开花物候与霜害风险开展回溯预测。 关键结果：以日序与阈值气温下的空气生长度日数为自变量的模型对开花进程的预测效果最优，其中岩梅与比格洛薹草的阈值气温为-4℃，越橘的阈值气温为-2℃。模型模拟的历史开花日期呈现显著提前的趋势，但77年间的变化幅度极小（1.2~2.1天），并未显著提升春末/夏初晚霜引发的开花早期霜害风险。 结论：与该区域低海拔地区相比，3种美国东北部高山植物的物候提前趋势及其敏感性均相对平缓，且开花时间的微小偏移并未提升霜害风险。高海拔地区物候提前幅度有限的潜在原因包括：升温趋势更为平缓、随海拔升高云量增多，以及/或需冷量不足。