Department of Geography, Loughborough University, Loughborough LE11 3TU, UK.
Proc Biol Sci. 2013 Aug 21;280(1769):20131278. doi: 10.1098/rspb.2013.1278. Print 2013 Oct 22.
Lakes are a central component of the carbon cycle, both mineralizing terrestrially derived organic matter and storing substantial amounts of organic carbon (OC) in their sediments. However, the rates and controls on OC burial by lakes remain uncertain, as do the possible effects of future global change processes. To address these issues, we derived OC burial rates in (210)Pb-dated sediment cores from 116 small Minnesota lakes that cover major climate and land-use gradients. Rates for individual lakes presently range from 7 to 127 g C m(-2) yr(-1) and have increased by up to a factor of 8 since Euro-American settlement (mean increase: 2.8×). Mean pre-disturbance OC burial rates were similar (14-22 g C m(-2) yr(-1)) across all land-cover categories (prairie, mixed deciduous and boreal forest), indicating minimal effect of the regional temperature gradient (approx. 4 °C) on background carbon burial. The relationship between modern OC burial rates and temperature was also not significant after removal of the effect of total phosphorus. Contemporary burial rates were strongly correlated with lake-water nutrients and the extent of agricultural land cover in the catchment. Increased OC burial, documented even in relatively undisturbed boreal lake ecosystems, indicates a possible role for atmospheric nitrogen deposition. Our results suggest that globally, future land-cover change, intensification of agriculture and associated nutrient loading together with atmospheric N-deposition will enhance OC sequestration by lakes.
湖泊是碳循环的核心组成部分，既能矿化陆地衍生的有机物质，又能在其沉积物中储存大量有机碳（OC）。然而，湖泊中 OC 的埋藏速率和控制因素仍不确定，未来全球变化过程的可能影响也不确定。为了解决这些问题，我们从覆盖主要气候和土地利用梯度的 116 个明尼苏达州小湖泊的（210）Pb 定年沉积物核心中得出了 OC 埋藏速率。目前，个别湖泊的埋藏速率范围为 7 至 127 g C m(-2) yr(-1)，自欧洲裔美国人定居以来增加了多达 8 倍（平均增加 2.8×）。在所有土地覆盖类别（草原、混合落叶林和北方森林）中，预干扰 OC 埋藏速率相似（14-22 g C m(-2) yr(-1)），表明区域温度梯度（约 4°C）对背景碳埋藏的影响最小。在去除总磷影响后，现代 OC 埋藏速率与温度之间的关系也不显著。当代埋藏速率与湖水养分和集水区农业土地覆盖面积密切相关。即使在相对未受干扰的北方湖泊生态系统中也记录到 OC 埋藏增加，表明大气氮沉降可能起作用。我们的研究结果表明，在全球范围内，未来的土地利用变化、农业集约化以及相关的养分负荷加上大气 N 沉降将增强湖泊的 OC 封存。
