Mass budgets and stable isotope ratios of Ca and Mg in ecosystems along a 120 yr-old glacial retreat chronosequence in the subtropical Gongga mountains

通过植被演替稳定冰川退缩产生的裸露土壤对于减少山区滑坡、侵蚀和水风险至关重要。植被建立速度的主要驱动力是通过风化从基质中释放出钙和镁等营养物质并将其转移到植物中。我们建议，以确定从基板和纳入生物循环的钙和镁的释放率发生在亚热带冰川退缩时序与快速植被演替的森林在不到100年在中国。为了量化这些速率，我们将通过确定所有主要生态系统分区（矿物质土壤，有机层，植被）中Ca和Mg的总储量变化以及沿沿着Ca的整体沉积速率来建立质量平衡。120年的时间序列达到从裸露的土壤，在短距离的全林使用的空间时间替代的方法。为了阐明所观察到的储量变化背后的过程，我们将开发一种新的方法来确定44/42 Ca同位素比使用双穗的46 Ca和43 Ca，并建立一个公开的方法来确定26/24 Mg比在我们的实验室和测量稳定的同位素比的Ca和Mg在岩石，土壤，植物和生态系统的解决方案。由于风化，植物吸收，吸附，或浸出等过程中反映的稳定同位素比值的变化，我们期望通过同时建立质量预算和测定Ca和Mg的稳定同位素比值的过程中得到更好的理解。

The stabilization of bare soil originating from glacial retreat by vegetation succession is crucial for reducing landslide, erosion, and water risks in mountainous areas. A major driver of the speed of vegetation establishment is the release of nutrients like Ca and Mg from the substrate by weathering and their transfer to the plants. We propose to determine the rates with which release from substrate and incorporation into biological cycling of Ca and Mg occur at a subtropical glacial retreat chronosequence with fast vegetation succession to a forest in less than 100 yr in China. To quantify these rates, we will establish mass balances by determining the change of the total stocks of Ca and Mg in all major ecosystem compartments (mineral soil, organic layer, vegetation) and bulk deposition rates along a ca. 120-yr chronosequence reaching from bare soil to full forest at a short distance using a space-for-time-substitution approach. To elucidate the processes behind the observed stock changes, we will develop a new method to determine 44/42Ca isotope ratios using a double spike of 46Ca and 43Ca and establish a published method to determine 26/24Mg ratios in our laboratory and measure stable isotope ratios of Ca and Mg in rocks, soils, plants, and ecosystem solutions. Because processes like weathering, plant uptake, adsorption, or leaching are reflected by changes of the stable isotope ratios, we expect an improved process understanding by the simultaneous establishment of mass budgets and determination of stable isotope ratios of Ca and Mg.