Rhizosphere as driver of subsoil organic matter distribution and composition

根际作为底土有机质分布和组成的驱动因素

• 批准号: 233425617
• 负责人: Professorin Dr. Ingrid Kögel-Knabner, since 2/2020
• 金额: --
• 依托单位: Lehrstuhl für Bodenkunde
• 依托单位国家: 德国
• 项目类别: Research Units
• 财政年份: 2013
• 资助国家: 德国
• 起止时间: 2012-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/233425617?language=en
• 关键词: Rhizosphere; driver; subsoil; organic; matter

During the first phase of the research unit FOR1806 we demonstrated the large effect of rhizodeposition on the amount and composition of soil organic carbon in subsoils. As shown for the central research site Grinderwald and the regional sites, not only the amount of soil organic matter is considerably larger in the rhizosphere in comparison to the root free bulk soil, but also the chemical composition is different. For Grinderwald we found clear chemical differences between rhizosphere and bulk soil for both particulate as well as clay associated SOM. The rhizosphere soil showed lower C/N ratios and a higher contribution of less decomposed OM (indicated by higher O/N-alkyl C proportions) in the vicinity of roots. These first results point to an important role of rhizodeposition for the build-up of specific rhizosphere structures (macro and micro-aggregation) that may foster organic carbon storage in subsoils. However, it remains unclear to which extent rhizodeposition affects mineralogy-dependent aggregation and thereby influences subsoil organic carbon composition and storage. The objectives of the present proposal are to understand the influence of growing and dead roots on the composition, distribution and the amount of soil organic carbon in the subsoil and specifically in the subsoil rhizosphere. The main aspect will be the evolving spatial differentiation of the soil organic carbon distribution due to roots growing into previously root free subsoil. We will work on the implementation of new methods to study zonal gradients around living and dead roots, as these zones play an important role in soil aggregation and thus also OM stabilization. These effects lead to increased spatial heterogeneities in subsoils in contrast to organic rich topsoils. To study these effects and mechanisms it is crucial to use controlled environmental conditions as can only be achieved under laboratory conditions, based on the field soil data obtained in the first phase of the research unit. We will use a cascade of experiments with increasing complexity starting from artificial root systems to natural roots of beech seedlings. These are then cross-checked with the results from the investigations at the field sites of the research unit.

在第一阶段的研究单位FOR 1806，我们证明了根沉积的数量和组成的土壤有机碳在底土的巨大影响。如中央研究点Grinderwald和区域研究点所示，与无根的散装土壤相比，根际土壤有机质的量不仅大得多，而且化学成分也不同。对于Grinderwald，我们发现明确的化学差异，根际和散装土壤颗粒以及粘土相关的SOM。根际土壤表现出较低的C/N比和较高的贡献较少分解OM（表示较高的O/N-烷基C比例）在根附近。这些第一个结果指出了一个重要的作用，根际沉积的特定根际结构（宏观和微观聚集）的建立，可能会促进有机碳储存在底土。然而，目前还不清楚在何种程度上根沉积影响矿物学依赖的聚集，从而影响底土有机碳的组成和存储。本提案的目的是了解生长和死亡的根的组成，分布和数量的土壤有机碳在底土，特别是在底土根际的影响。主要方面将是不断演变的空间差异的土壤有机碳分布，由于根生长到以前无根底土。我们将致力于实施新的方法来研究活根和死根周围的地带梯度，因为这些地带在土壤聚集中起着重要作用，因此也是OM稳定。这些影响导致增加的空间异质性，在底土中的有机丰富的表土。为了研究这些影响和机制，关键是要根据研究单位第一阶段获得的实地土壤数据，使用只能在实验室条件下实现的受控环境条件。我们将使用一系列复杂性不断增加的实验，从人工根系到山毛榉幼苗的自然根系。然后将这些数据与研究单位实地调查的结果进行交叉核对。