Abstract Secondary forests are a huge carbon sink in terrestrial ecosystems, but it remains unclear whether growth of secondary forests has accelerated or decelerated due to global environmental changes, especially in East Asia. In this study, we analysed 30 years of data at 26 permanent plots along a secondary succession of temperate forest in central Japan to test whether the aboveground biomass (AGB) growth of secondary forest has accelerated or decelerated. The AGB–age relationship has clearly shifted upwards from the 1980s to the 2010s. The observed annual net AGB change (ΔAGB) was higher than that expected from the AGB–age relationship. These results indicate that ΔAGB has accelerated. However, the observed ΔAGB adjusted for the effects of stand age has gradually decreased from the 1980s to the 2010s. This indicates that ΔAGB of the secondary forest had accelerated prior to the 1980s, and decelerated after the 1980s. The decrease in ΔAGB after the 1980s was due to decreased biomass gain in the 1990s and increased mortality after the 1990s. Climatic factors are not considered the driver of the acceleration of ΔAGB because mean annual temperature and annual precipitation at the study site was relatively stable before 1980. However, mean annual temperature has increased since the 1980s and annual precipitation was low in the 1990s, which would result in increased drought stress and may have contributed to the decrease in biomass gain in the 1990s. Other abiotic and biotic stresses may also have contributed to the increased mortality after the 2000s. This study revealed a long-term transition from an acceleration phase to a deceleration phase of forest growth, indicating that forest growth changes relating anthropogenic environmental changes since mid-20th century are not necessarily unidirectional.

中文翻译：

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日本中部温带森林地上生物量积累速率的加速和减速

摘要 次生林是陆地生态系统中巨大的碳汇，但由于全球环境变化，尤其是东亚地区，次生林的生长是加速还是减速尚不清楚。在这项研究中，我们分析了日本中部温带森林次生演替沿线 26 个永久地块的 30 年数据，以测试次生林的地上生物量 (AGB) 增长是加速还是减速。AGB 与年龄的关系从 1980 年代到 2010 年代明显向上转移。观察到的年度净 AGB 变化 (ΔAGB) 高于 AGB 与年龄关系的预期值。这些结果表明ΔAGB 已经加速。然而，从 1980 年代到 2010 年代，针对林龄影响调整的观察到的 ΔAGB 逐渐下降。这表明次生林的ΔAGB在1980年代之前加速，1980年代之后减速。1980 年代之后 ΔAGB 的减少是由于 1990 年代生物量增加减少和 1990 年代之后死亡率增加。气候因素不被认为是ΔAGB加速的驱动因素，因为研究地点的年平均气温和年降水量在1980年代之前相对稳定。但是，自1980年代以来，年均气温升高，1990年代年降水量偏低，这将导致导致干旱压力增加，并可能导致 1990 年代生物量增加的减少。其他非生物和生物胁迫也可能导致 2000 年代后死亡率的增加。