Data from: Tree-growth is more sensitive than species distributions to recent changes in climate and acidic deposition in the northeastern United States

Tree-growth responses to environmental change could provide early detection of shifts in forest composition and help facilitate ecosystem management and conservation.
We studied forest tree responses to recent trends in climate and acidic deposition using analyses of tree rings and long-term climate, deposition and forest plot data along an elevational climatic gradient in the northeastern United States. We analyzed how (a) individual growth of dominant species (Picea rubens, Abies balsamea), and (b) spatial distributions of all species, changed with elevation over time due to changing environment.
We observed a mean 220 m upslope shift of temperature envelopes since the 1960s, consistent with regional climate warming, but found no evidence of synchronous upslope shifts in species abundance. Species’ ranges were stable although some leaned upslope or downslope, suggesting species-specific migration lags or controls on species’ ranges.
Compared to species distributions, the growth of dominant species was more responsive to environmental change. Although the basal area of P. rubens declined within its range since the 1960s, its growth has increased recently with increasing precipitation pH and to a lesser extent with warming climate. Abies balsamea has gradually increased in both basal area and density since the 1960s, with its growth responding to precipitation pH but not climate. Historically, P. rubens grew better at lower and A. balsamea at higher elevations, but these elevation effects appeared to be mediated primarily by moisture, and have disappeared over time.
Synthesis and applications. Mean tree-growth responses to changing climate (temperature, moisture) and precipitation chemistry were more consistent and more clearly detectable than shifts in tree species’ ranges, suggesting that monitoring tree growth across climatically-controlled species’ ranges (e.g. along elevational or latitudinal gradients) may provide a powerful tool for early detection of potential future changes in forest composition in a changing environment.

树木生长对环境变化的响应，可为森林组成的转变提供早期预警，并助力生态系统管理与保护工作。
本研究依托美国东北部沿海拔气候梯度 (elevational climatic gradient) 的树木年轮 (tree rings) 分析，以及长期气候、酸性沉降 (acidic deposition) 与森林样地数据，探究了林木对近期气候与酸性沉降变化的响应。我们分析了两个研究维度：其一为优势树种（红云杉 (Picea rubens)、香脂冷杉 (Abies balsamea)）的单株生长动态，其二为所有树种的空间分布随环境改变，随海拔与时间的演变规律。
研究发现，自20世纪60年代以来，物种温度适宜范围 (temperature envelopes) 的平均上移幅度达220米，与区域气候变暖的趋势一致，但未观测到物种丰度同步向高海拔迁移的现象。尽管部分物种存在向高海拔或低海拔偏移的趋势，但整体物种分布区保持稳定，这提示物种存在物种特异性的迁移滞后效应，或其分布范围受到特定因素的调控。
相较于物种分布格局，优势树种的生长对环境变化的响应更为显著。自20世纪60年代以来，尽管红云杉分布区内的胸高断面积 (basal area) 有所下降，但近年来其生长量随降水pH值升高而提升，气候变暖对其生长的影响相对较弱。香脂冷杉自20世纪60年代以来，胸高断面积与种群密度均逐步上升，其生长量受降水pH值调控，但与气候因素无关。历史上，红云杉在低海拔区域生长更佳，而香脂冷杉则更适应高海拔环境，但这类海拔效应主要由水分条件介导，且随时间推移已逐渐消失。
综合与应用。相较于树种分布区的变化，林木生长对气候变化（温度、水分）与降水化学性质的响应更为一致且更易被检测。这表明，在受气候调控的物种分布区内（例如沿海拔或纬度梯度）开展林木生长监测，可为全球变化背景下森林组成的潜在未来变化提供强有力的早期预警工具。