Many forest soils are acidic and have very low plant-available pools of magnesium. Past and present sylvicultural, nutritional and/or climatic pressures endured by forest ecosystems can result in net losses of nutrients and ecosystem function losses. Liming with a carbonate product is an alternative to counteract these degradations but the effects of liming on the biogeochemical cycling of nutrients over time and the dynamics of Mg released from liming products are still unclear. We studied the Mg isotopes composition in four paired-treatment experimental beech forest ecosystems in northern France. At the sites where dolomitic lime was applied, the variation in exchangeable and foliar δ²⁶Mg demonstrated the direct contribution of dolomite-derived Mg to the replenishment of topsoil exchangeable pools and to tree nutrition improvement: dolomite-derived Mg was incorporated into the biological cycling which allows its retention on the mid to long term in the soil–plant system. At the sites limed with calcium carbonate, the changes in exchangeable and foliar Mg contents and δ²⁶Mg observed on the long term suggest that the applied product contained a small amount of Mg and/or that Mg cycling changed after liming, to cope in particular with the low Mg availability. Lastly, our results highlight the high δ²⁶Mg of the organic layer (humus): fractionation processes occurring within this layer (mineralization/ageing of organic matter, preferential retention of ²⁶ Mg) could explain these singular signatures that could greatly influence the topsoil Mg exchangeable pools.

许多森林土壤是酸性的，植物体内可利用的镁含量非常低。森林生态系统所承受的过去和现在的森林，营养和/或气候压力可能导致养分净损失和生态系统功能损失。用碳酸盐产品撒石灰是抵消这些降解的另一种方法，但是石灰对养分随时间推移养分的生物地球化学循环的影响以及从石灰产物中释放的镁的动力学仍不清楚。我们研究了法国北部四个配对处理的山毛榉森林生态系统中的镁同位素组成。在这里白云石石灰应用，在可交换的变化和叶面δ网站²⁶镁证明了白云石衍生的镁对表土可交换池的补充和树木营养改善的直接贡献：白云石衍生的镁被纳入生物循环，从而使其在土壤-植物系统中长期保留。在用碳酸钙石灰的位点，在可交换和叶面Mg含量和δ的变化²⁶的Mg的长期观察表明，所施加的产物含有Mg的少量和/或Mg的循环石灰之后改变，特别是，以应付镁的可用性低。最后，我们的结果突出了高δ ²⁶ Mg的有机层的（腐殖质）：发生在此层内分馏过程（矿化/有机物老化，优先保留²⁶ 镁）可以解释这些可能极大影响表土镁可交换池的奇异特征。