School of Geography, University of Leeds, Leeds LS2 9JT, UK.
Department of Geography, University College London, London WC1E 6BT, UK.
Nature. 2017 Feb 2;542(7639):86-90. doi: 10.1038/nature21048. Epub 2017 Jan 11.
Peatlands are carbon-rich ecosystems that cover just three per cent of Earth's land surface, but store one-third of soil carbon. Peat soils are formed by the build-up of partially decomposed organic matter under waterlogged anoxic conditions. Most peat is found in cool climatic regions where unimpeded decomposition is slower, but deposits are also found under some tropical swamp forests. Here we present field measurements from one of the world's most extensive regions of swamp forest, the Cuvette Centrale depression in the central Congo Basin. We find extensive peat deposits beneath the swamp forest vegetation (peat defined as material with an organic matter content of at least 65 per cent to a depth of at least 0.3 metres). Radiocarbon dates indicate that peat began accumulating from about 10,600 years ago, coincident with the onset of more humid conditions in central Africa at the beginning of the Holocene. The peatlands occupy large interfluvial basins, and seem to be largely rain-fed and ombrotrophic-like (of low nutrient status) systems. Although the peat layer is relatively shallow (with a maximum depth of 5.9 metres and a median depth of 2.0 metres), by combining in situ and remotely sensed data, we estimate the area of peat to be approximately 145,500 square kilometres (95 per cent confidence interval of 131,900-156,400 square kilometres), making the Cuvette Centrale the most extensive peatland complex in the tropics. This area is more than five times the maximum possible area reported for the Congo Basin in a recent synthesis of pantropical peat extent. We estimate that the peatlands store approximately 30.6 petagrams (30.6 × 10 grams) of carbon belowground (95 per cent confidence interval of 6.3-46.8 petagrams of carbon)-a quantity that is similar to the above-ground carbon stocks of the tropical forests of the entire Congo Basin. Our result for the Cuvette Centrale increases the best estimate of global tropical peatland carbon stocks by 36 per cent, to 104.7 petagrams of carbon (minimum estimate of 69.6 petagrams of carbon; maximum estimate of 129.8 petagrams of carbon). This stored carbon is vulnerable to land-use change and any future reduction in precipitation.
泥炭地是富含碳的生态系统，仅覆盖地球陆地表面的 3%，但却储存了三分之一的土壤碳。泥炭土是由在水淹缺氧条件下部分分解的有机物质积累形成的。大多数泥炭地位于气候凉爽的地区，那里不受阻碍的分解速度较慢，但在一些热带沼泽森林下也有沉积物。在这里，我们展示了来自世界上最广泛的沼泽森林地区之一的实地测量结果，即刚果盆地中部的库维特中央洼地。我们在沼泽森林植被下发现了广泛的泥炭沉积物（泥炭定义为有机物质含量至少为 65%且深度至少为 0.3 米的物质）。放射性碳测年表明，泥炭始于大约 10600 年前，与全新世初期非洲中部更湿润条件的开始相吻合。泥炭地占据了大型的河间盆地，似乎主要是由雨水补给的，类似于寡营养状态的系统（营养状态低）。尽管泥炭层相对较浅（最大深度为 5.9 米，中位数深度为 2.0 米），但通过结合现场和遥感数据，我们估计泥炭面积约为 145500 平方公里（95%置信区间为 131900-156400 平方公里），使库维特中央成为热带地区最大的泥炭地复合体。这个面积是最近对热带泛泥炭地范围综合分析中报道的刚果盆地最大可能面积的五倍多。我们估计，泥炭地地下储存了约 306 太克（306×10 克）的碳（95%置信区间为 6.3-46.8 太克的碳）——这一数量与整个刚果盆地的热带森林的地上碳储量相当。我们对库维特中央的研究结果使全球热带泥炭地碳储量的最佳估计增加了 36%，达到 1047 太克（碳最低估计值为 696 太克；碳最高估计值为 1298 太克）。这些储存的碳容易受到土地利用变化和未来降水减少的影响。
