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，可为森林群落组成转变的早期预警提供支撑，同时助力生态系统管理与保护实践。
本研究依托美国东北部沿海拔气候梯度（elevational climatic gradient）布设的长期森林样地数据、气候与酸性沉降（acidic deposition）监测资料，结合树木年轮（tree rings）分析方法，探究了林木对近期气候与酸性沉降变化的响应特征。本研究分析了两个维度的变化：一是优势树种——红云杉（Picea rubens）与香脂冷杉（Abies balsamea）的个体生长动态，二是所有物种的空间分布格局，如何随海拔梯度及环境变化随时间推移发生改变。
研究结果显示，自20世纪60年代以来，温度适宜区平均向坡上迁移了220米，这与区域气候变暖的趋势相符，但未观测到物种丰度同步向坡上迁移的证据。尽管部分物种呈现出向坡上或坡下偏移的趋势，但整体物种分布范围保持稳定，这暗示存在物种特异性的迁移滞后效应，或存在调控物种分布范围的机制。
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，红云杉在其原生分布范围内的胸高断面积（basal area）有所下降，但近期其生长量随降水pH值升高而提升，同时受气候变暖的影响程度相对较轻。香脂冷杉的胸高断面积与种群密度自20世纪60年代以来均呈逐步上升趋势，其生长量响应降水pH值变化，但不受气候因素调控。历史上，红云杉在低海拔区域生长更佳，而香脂冷杉则更适配高海拔环境，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。
综合与应用启示：相较于林木物种分布范围的变化，树木生长对气候变化（温度、水分）与降水化学特征的响应更为一致且更易被精准检测。这表明，在受气候调控的物种分布范围内（例如沿海拔或纬度梯度布设的监测样带）开展林木生长监测，或可成为一种高效手段，用于早期预警环境变化背景下未来森林群落组成的潜在转变。