Ecosystem nutrition as driver of soil organic matter turnover, a modelling approach

长期的生态系统监测表明，大气中CO2的增加和持续的氮（N）沉降可能会迫使森林生态系统进入磷（P）限制，对森林功能产生重大影响。然而，过程控制的生物有效性的P，其依赖于土壤发育和风化没有得到充分的理解。在其第一阶段，SPP 1685收集了一个独特的数据集，在获取（即主要是风化驱动的P可用性）和回收（即主要是有机物驱动的P可用性）生态系统中的P循环。我们建议开发一个新的过程为基础的，土壤地球化学模型的C，N和P的循环，将这些意见与主要的土壤地球化学过程的数学表示，从而把意见到一个一致的框架。我们假设，土壤有机质周转是关键，以维持生态系统养分沿着梯度的P有效性。为了更好地了解不同水平的磷有效性的土壤碳的动态，我们将添加一些关键的分析，在这些森林土壤中使用14 C技术的碳周转。该模型将建立在现有的土壤有机碳周转，运输和稳定的土壤柱模型，并代表有机和无机N和P循环以及植物和微生物的差异养分获取策略。利用这一模型，我们将研究不同水平的磷供应的影响，特别是土壤有机质的储存和周转对生物磷有效性的作用。在试图保持模型简单的同时，实施的过程应该能够正确预测SPP 1685第二阶段计划的实验施肥的生态系统响应。该模型的发展将有助于更好地了解磷获取和循环生态系统之间的转变的根本原因，并提供了潜在的应用这一知识的区域和森林生态系统的CO2施肥和N沉积的研究。

Long-term ecosystem monitoring suggests that increasing atmospheric CO2 and continued nitrogen (N) deposition may drive forest ecosystems into phosphorus (P) limitation, with significant impacts on forest functioning. However, the processes controlling the biological availability of P, and their dependence on soil development and weathering are not sufficiently understood. In its first phase, the SPP 1685 has collected a unique data set on P cycling in acquiring (i.e. predominantly weathering-driven P availability) and recycling (i.e. predominantly organic-matter-driven P availability) ecosystems. We propose to develop a novel process-based, biogeochemical soil model of the C, N, and P cycles to integrate these observations with a mathematical representation of the major biogeochemical processes, and thereby to put the observations into one consistent framework. We hypothesise that soil organic matter turnover is pivotal to maintain ecosystem nutrition along the gradient of P availability. To better understand the soil C dynamics at different levels of P availability, we will add some critical analyses on the C turnover in these forest soils using the 14C technique. The model will be built on an existing model of soil organic C turnover, transport, and stabilisation in the soil column, and represent the organic and inorganic N and P cycle as well as differential nutrient acquisition strategies of plants and microbes. With this model, we will study the effects of different levels of P supply, in particular the role of soil organic matter storage and turnover on biological P availability. While trying to keep the model simple, the processes implemented should be able to correctly predict ecosystem responses to the experimental fertilization planned in the second phase of the SPP 1685. The model development will contribute to a better understanding of the underlying causes for the shift between P acquiring and recycling ecosystems, and offer the potential to apply this knowledge regionally and for the study of CO2 fertilization and N deposition on forest ecosystems.