Climate change is shifting the phenological cycles of plants1, thereby altering the functioning of ecosystems, which in turn induces feedbacks to the climate system2. In northern (north of 30° N) ecosystems, warmer springs lead generally to an earlier onset of the growing season3,4 and increased ecosystem productivity early in the season5. In situ6 and regional7–9 studies also provide evidence for lagged effects of spring warmth on plant productivity during the subsequent summer and autumn. However, our current understanding of these lagged effects, including their direction (beneficial or adverse) and geographic distribution, is still very limited. Here we analyse satellite, field-based and modelled data for the period 1982–2011 and show that there are widespread and contrasting lagged productivity responses to spring warmth across northern ecosystems. On the basis of the observational data, we find that roughly 15 per cent of the total study area of about 41 million square kilometres exhibits adverse lagged effects and that roughly 5 per cent of the total study area exhibits beneficial lagged effects. By contrast, current-generation terrestrial carbon-cycle models predict much lower areal fractions of adverse lagged effects (ranging from 1 to 14 per cent) and much higher areal fractions of beneficial lagged effects (ranging from 9 to 54 per cent). We find that elevation and seasonal precipitation patterns largely dictate the geographic pattern and direction of the lagged effects. Inadequate consideration in current models of the effects of the seasonal build-up of water stress on seasonal vegetation growth may therefore be able to explain the differences that we found between our observation-constrained estimates and the model-constrained estimates of lagged effects associated with spring warming. Overall, our results suggest that for many northern ecosystems the benefits of warmer springs on growing-season ecosystem productivity are effectively compensated for by the accumulation of seasonal water deficits, despite the fact that northern ecosystems are thought to be largely temperature- and radiation-limited10.Widespread but contrasting delayed responses of ecosystem productivity to spring warmth across northern ecosystems is inferred from satellite data, with higher areal fractions of adverse effects than beneficial effects.

中文翻译：

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春季变暖对北方植物生产力的广泛季节性补偿效应

气候变化正在改变植物的物候循环 1，从而改变生态系统的功能，进而导致对气候系统的反馈 2。在北部（北纬 30° 以北）生态系统中，温暖的春季通常会导致生长季节提前开始 3,4 并在季节初期提高生态系统生产力 5。原位 6 和区域 7-9 研究也为春季温暖对随后夏季和秋季植物生产力的滞后影响提供了证据。然而，我们目前对这些滞后效应的了解，包括它们的方向（有利或不利）和地理分布，仍然非常有限。这里我们分析卫星，1982 年至 2011 年期间基于实地和建模的数据，并表明北方生态系统对春季温暖的生产力反应普遍存在且形成鲜明对比。根据观测数据，我们发现在大约 4100 万平方公里的总研究区域中，大约 15% 的区域表现出不利的滞后效应，而总研究区域的大约 5% 的区域表现出有益的滞后效应。相比之下，当代陆地碳循环模型预测不利滞后效应的面积比例要低得多（范围从 1% 到 14%），而有益滞后效应的面积分数要高得多（范围从 9% 到 54%）。我们发现海拔和季节性降水模式在很大程度上决定了滞后效应的地理模式和方向。因此，当前模型中对水分胁迫的季节性累积对季节性植被生长影响的考虑不足可能能够解释我们发现的观察约束估计值与模型约束的与春季相关的滞后效应估计值之间的差异变暖。总体而言，我们的研究结果表明，对于许多北方生态系统而言，温暖的春季对生长季节生态系统生产力的好处被季节性缺水的累积有效补偿，尽管北方生态系统被认为在很大程度上受到温度和辐射的限制10 .从卫星数据推断，生态系统生产力对整个北方生态系统春季温暖的广泛但对比延迟的反应，