Forest Research Center INIA-CIFOR, Madrid, Spain.
Harvard Forest, Harvard University, Petersham, MA, USA.
Sci Total Environ. 2021 Apr 15;765:142737. doi: 10.1016/j.scitotenv.2020.142737. Epub 2020 Oct 8.
Most information on the ecology of oak-dominated forests in Europe comes from forests altered for centuries because remnants of old-growth forests are rare. Disturbance and recruitment regimes in old-growth forests provide information on forest dynamics and their effects on long-term carbon storage. In an old-growth Quercus petraea forest in northwestern Spain, we inventoried three plots and extracted cores from 166 live and dead trees across canopy classes (DBH ≥ 5 cm). We reconstructed disturbance dynamics for the last 500 years from tree-ring widths. We also reconstructed past dynamics of above ground biomass (AGB) and recent AGB accumulation rates at stand level using allometric equations. From these data, we present a new tree-ring-based approach to estimate the age of carbon stored in AGB. The oldest tree was at least 568 years, making it the oldest known precisely-dated oak to date and one of the oldest broadleaved trees in the Northern Hemisphere. All plots contained trees over 400 years old. The disturbance regime was dominated by small, frequent releases with just a few more intense disturbances that affected ≤20% of trees. Oak recruitment was variable but rather continuous for 500 years. Carbon turnover times ranged between 153 and 229 years and mean carbon ages between 108 and 167 years. Over 50% of AGB (150 Mg·ha) persisted ≥100 years and up to 21% of AGB (77 Mg·ha) ≥300 years. Low disturbance rates and low productivity maintained current canopy oak dominance. Absence of management or stand-replacing disturbances over the last 500 years resulted in high forest stability, long carbon turnover times and long mean carbon ages. Observed dynamics and the absence of shade-tolerant species suggest that oak dominance could continue in the future. Our estimations of long-term carbon storage at centennial scales in unmanaged old-growth forests highlights the importance of management and natural disturbances for the global carbon cycle.
欧洲栎树主导森林的生态信息大多来自于已经改变了几个世纪的森林，因为古老森林的残余物非常罕见。在古老的栎树林中，干扰和繁殖制度为森林动态及其对长期碳储存的影响提供了信息。在西班牙西北部的一个老栎树-Quercus petraea 森林中，我们对三个样地进行了清查，并从树冠层（DBH≥5cm）的 166 株活树和死树上提取了芯材。我们根据树木年轮宽度重建了过去 500 年的干扰动态。我们还使用了种间关系方程来重建过去的地上生物量（AGB）和最近的林分水平 AGB 积累速率。根据这些数据，我们提出了一种新的基于树木年轮的方法来估计 AGB 中储存的碳的年龄。最古老的树至少有 568 年，使其成为迄今为止最古老的、有确切日期的栎树之一，也是北半球最古老的阔叶树之一。所有样地都包含 400 岁以上的树木。干扰制度以小而频繁的释放为主，只有少数几次更强烈的干扰影响了≤20%的树木。栎树的繁殖情况各不相同，但在 500 年内相对连续。碳周转时间在 153 到 229 年之间，平均碳年龄在 108 到 167 年之间。超过 50%的 AGB（150Mg·ha）持续存在≥100 年，高达 21%的 AGB（77Mg·ha）持续存在≥300 年。低干扰率和低生产力维持了当前的林冠栎树主导地位。在过去的 500 年中，没有管理或取代林分的干扰，导致了森林的高度稳定，碳的长期周转和平均碳年龄的延长。观察到的动态和缺乏耐荫物种表明，栎树的主导地位可能在未来继续存在。我们对未经管理的古老森林在百年尺度上的长期碳储存的估计，突出了管理和自然干扰对全球碳循环的重要性。
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