This study presents the relationship between inputs of elements (especially biominerals), their recycling mechanisms and the average residence time of the major elements in mull humus.

In forest ecosystems with generally low element inputs, decomposing leaf litter is an important source of soil nutrients. While the processes and the release speeds of elements, such as C, N and P, are well determined during litter degradation, less is known about elements like Fe, Al, Mg, Mn, Si, Ca, K, or Na, some of which are essential for tree nutrition.

The objective of this study was to determine the average residence time of these elements in mull-type humus for 3 different soils: a Dystric Cambisol (S1), Eutric Cambisol (S2) and Rendzic Leptosol (S3), in the same beech grove of the northeast of France and to identify the main mechanisms controlling them.

To achieve this goal, the approach used: 1) scanning electron microscope observation of the evolution and recycling of elements during litter degradation; 2) quantification of total inputs and their form (soluble/insoluble) in the litterfall and the contribution of exploitation residues; 3) quantification and evolution of litter stocks; and 4) calculation and comparison of the residence time of the elements according to their form.

Calculation of inputs and stocks of elements in humus made it possible to assess the residence time of each elements. The average residence times were between 58.4 and 13.1 y for Fe and Al; 3.3 and 1.6 y for Si, N, S and Ca; 2.2 and 1.2 y for Mn, Mg, Na, P and C; and 0.6 and 0.8 y for K. The results were similar for the three soils except for the Mn stock and inputs, which were lower in S3, and for the Si input, which decreased from S1 to S3.

The results of the study indicate that the residence times of K, P, Na, Mg and S decreased with the percentage of soluble forms. Conversely, they increased when elements were principally in the form of biominerals (Si, Ca), such as in plant tissues, organic molecules (N) and more resistant tissues, or intervened in sorption mechanisms (Al, Fe) and biotic recycling mechanisms, such as testate amoebae (Si, Ca, P, Mn) and fungal hyphae (Ca, Mn, P) and abiotic precipitation (Si).

这项研究提出了元素（尤其是生物矿物质）的输入，其循环利用机制以及主要元素在腐殖质中的平均停留时间之间的关系。

在元素输入量通常较低的森林生态系统中，分解枯枝落叶是土壤养分的重要来源。尽管在凋落物降解过程中可以很好地确定元素（例如C，N和P）的过程和释放速度，但对诸如Fe，Al，Mg，Mn，Si，Ca，K或Na等元素的了解却很少。这是树木营养必不可少的。

这项研究的目的是确定在3种不同土壤中，杂种腐殖质中这些元素的平均停留时间：Dystric Cambisol（S1），Eutric Cambisol（S2）和Rendzic Leptosol（S3）在相同的山毛榉林中。法国东北部，并确定控制它们的主要机制。

为了实现这一目标，采用了以下方法：1）扫描电子显微镜观察凋落物降解过程中元素的演变和循环利用；2）量化凋落物中总投入及其形式（可溶/不溶）和开采残留物的贡献；3）凋落物种群的量化和演变；4）根据元素的形式计算和比较元素的停留时间。

腐殖质中元素的投入和存量的计算使评估每个元素的停留时间成为可能。Fe和Al的平均停留时间在58.4和13.1 y之间。Si，N，S和Ca为3.3和1.6 y；Mn，Mg，Na，P和C为2.2和1.2 y; 三种土壤的结果相似，除了锰含量和投入量（在S3中较低）和硅投入量（从S1降至S3）外，这三种土壤的结果相似。

研究结果表明，K，P，Na，Mg和S的停留时间随可溶性形式的百分比而减少。相反，当元素主要以生物矿物质（Si，Ca）的形式（例如在植物组织，有机分子（N）和更具抵抗力的组织中）或干预吸附机制（Al，Fe）和生物循环机制时，它们增加，如睾丸变形虫（Si，Ca，P，Mn）和真菌菌丝（Ca，Mn，P）和非生物沉淀（Si）。