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

鉴定根际格局的先决条件是根在生长过程中就地定位。根作为径向输运过程的汇和/或源，是格局形成的起点。与此同时，它们通过改变其邻近地区的土壤结构，不断改变运输的边界条件。在第一阶段，我们研究了根系结构（RSA）随时间的变化，以及在根段或根系尺度上，长毛的缺失在多大程度上导致了补偿机制，以及模式形成（物理和化学）的差异是否作为土壤基质（沙土与壤土）的函数而发生。我们将观察到的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有关。基质对根系性状的总体影响（P1），特别是对根径和根分解的影响大得惊人。因此，在第二阶段，我们将专注于破译这些根直径和分解变化的机制，以及它们对化学梯度、生物孔循环和碳通量等模式形成的影响。乙烯可以诱导根系出现“根径增大”现象。乙烯浓度的变化可能是由乙烯生产和/或乙烯在根际扩散的变化引起的。在一系列的实验室实验中，我们将测试这些变化是否确实发生，以及它们是否与土壤力学特性或根-土接触有关。后者被认为在两个底物之间有系统的不同。根系降解的差异也可能与乙烯有关，因为几何形状的改变以及化学成分的改变会影响腐烂，从而影响碳通量。在这些实验室实验中，我们将测量土壤气相中的乙烯浓度，不同直径等级的根与土壤的接触面积以及根的腐烂。我们还将研究生物孔中的根直径以及径向化学梯度是如何受到影响的。这些实验将与其他伙伴合作进行，同时分析参与乙烯合成和信号传导的根基因（P7, P8），以及改变根际乙烯浓度的土壤微生物群（P14, P17）。土壤机械阻抗（P23）将被表征，根系渗出（P11）将被测量。乙烯在系统中的扩散将根据测量的土壤结构用P4模拟。对于根衰变和碳通量，我们与P19合作。土壤小区试验将被用来研究土壤结构的长期变化，如生物孔密度的积累及其对渗透能力和保水能力的影响，这是田间规模上的一个新兴特性。

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.