Relevance of root growth and related soil structure formation for spatiotemporal patterns of chemical and biological properties and emergent system functions

确定根际模式的一个先决条件是根在生长过程中的原位定位。根部是径向输运过程的汇和/或源，是图案形成的起点。在第一阶段中，我们研究了根系结构(RSA)随时间的变化，长毛的缺乏在多大程度上导致了根段或根系尺度上的补偿机制，以及格局形成(物理和化学)的差异是否作为土壤基质(沙土和壤土)的函数而发生。我们观察到植物系统尺度上的变化与养分吸收、生物量生产和土壤入渗作为新出现的特性相关联。基质对一般根系性状(P1)、特别是对根直径和根分解的影响令人惊讶地大。因此，在第二阶段，我们将重点破译这些根直径和分解的变化及其对格局形成的影响的机制，如化学梯度、生物孔循环和碳通量。乙烯能诱导根“增粗”。乙烯浓度的变化可能是由于乙烯产量的变化和/或根际乙烯扩散的变化造成的。在一系列的实验室实验中，我们将测试这种变化是否确实发生，以及它们是否与土壤的力学性质或根-土接触有关。后者被认为在两种底物之间有系统地不同。根的降解差异也可能与乙烯有关，因为改变的几何形状和改变的化学成分会影响腐烂，从而影响碳通量。在这些实验室实验中，我们将测量不同直径级别的根的土壤气相和根-土接触面积中的乙烯浓度以及根的腐烂。我们还将调查生物孔中的根直径以及径向化学梯度是如何受到影响的。这些实验将与其他合作伙伴合作，同时分析参与乙烯合成和信号传递的根基因(P7、P8)，以及改变根际乙烯浓度的土壤微生物群(P14、P17)。将对土壤机械阻抗(P23)进行表征，并测量根分泌物(P11)。乙烯在系统中的扩散将由P4根据测量的土壤结构进行建模。在根腐烂和碳通量方面，我们与P19合作，将利用土壤小区实验来研究土壤结构的长期变化，如生物孔密度的增加及其对渗透能力和水分保持能力的影响，作为田间尺度上的紧急特性。

A prerequisite for identification of patterns in the rhizosphere is the localization of roots in situ as they grow. Roots, being sinks and/or sources of radial transport processes, are the starting point for pattern formation. At the same time they constantly alter boundary conditions for transport through soil structure modifcations in their immediate vicinity.In phase 1 we addressed root system architecture (RSA) over time and the extent to which the absence of elongated hairs leads to compensatory mechanisms at the root segment or root system scale and whether differences in pattern formation (physical and chemical) occur as a function of soil substrate (sand vs. loam). We related observed changes at the plant system scale to nutrient uptake, biomass production and soil infiltration as emerging properties.Substrate showed a surprisingly large effect on root traits in general (P1) and on root diameter and root decomposition in particular. Therefore in phase 2, we will focus on deciphering the mechanisms underlying these changes in root diameter and decomposition and their consequences for pattern formation such as chemical gradients, biopore recycling and carbon flux. The root phene ‘increased root diameter’ can be induced by ethylene. Changes in ethylene concentration may result from changes in ethylene production and/or changes in ethylene diffusion in the rhizosphere. In a series of lab experiments we will test, whether such changes do occur and whether they can be related to soil mechanical properties or root-soil contact. The latter is supposed to differ systematically between the two substrates. Differences in root degradation may also be related to ethylene as altered geometry as well as altered chemical composition will affect decay and hence carbon flux.In these lab experiments we will measure ethylene concentration in the soil gas phase and the root-soil contact area for roots of different diameter classes as well as root decay. We will also investigate root diameters in biopores and how radial chemical gradients are affected. The experiments will be conducted in cooperation with other partners for simultaneous analyses of root genes involved in ethylene synthesis and signalling (P7, P8), and soil microbiota altering rhizosphere ethylene concentrations (P14, P17). Soil mechanical impedance (P23) will be characterised and root exudation (P11) will be measured. Ethylene diffusion in the system will be modelled by P4 based on measured soil structure. For root decay and carbon flux we cooperate with P19.The soil plot experiment will be harnessed to investigate long-term changes in soil structure like the build-up of biopore density and its consequences for infiltration capacity and water retention as an emergent property at the field scale.