Spatial segregation, substrate and nutrient availability as limiting factors for subsoil C-turnover

空间隔离、基质和养分有效性作为底土碳周转的限制因素

• 批准号: 233441010
• 负责人: Professor Dr. Bernd Marschner
• 金额: --
• 依托单位: Geographisches Institut
• 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 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/233441010?language=en
• 关键词: Spatial; segregation; substrate; nutrient; availability

The spatial heterogeneity of subsoil C distribution and fluxes is much higher than in topsoils due to the greater relevance of preferential flow paths, roots, and animal burrows for C-inputs. The spatial segregation of consumers and substrate therefore is more a rule than an exception in subsoils. Taken as an explanation for the observed homogenization effects and for slow turnover rates in subsoils, this implies that hot spots are rather static and "cold regions" remain uninhabited despite substrate availability for extended periods of time. The rhizosphere soil is such a hot spot where C-inputs alter SOC composition and stimulate microbial and enzyme activities. On the other hand, microbial activity in the subsoil appears to be limited by nutrient availability, as indicated by enzyme activity patterns and incubation experiments performed during the first phase. Fresh substrate inputs in the rhizosphere may thus provide energy for microorganisms to produce enzymes for acquiring these limiting nutrients, or they may aggravate N- and P-limitations and thus lead to the accumulation of root-borne organic matter in the rhizosphere. The main objective of the activities outlined in this proposal is to investigate the factors limiting the degradation of subsoil SOC and thus contribute to resolving the contradictory findings of relatively high mineralisation rates in incubation experiments despite the high apparent 14C age of subsoil SOC. The explanatory mechanism of spatial separation between consumers and substrates will be addressed by applying new imaging techniques for analysing spatial patterns of enzyme activities and substrate mineralization in undisturbed soil samples from different depths at various sites. Another focus of this project will be on the characterization of hotspots of microbial activity, mainly the rhizosphere, regarding enzyme patterns and factors stimulating or limiting mineralization processes at these micro-sites relative to the bulk soil. By determining these rhizosphere effects and their spatial extension, important input parameters for the rhizosphere module of the COMISSION model (PC) will be made available. The analysis of 14CO2 in long-term incubation experiments will reveal, if only recent SOC inputs are mineralized or also "old" SOC is labile under these conditions. We will analyze enzyme activities in the soil solutions that are collected at the Grinderwald observatories to determine their translocation into the subsoil. Finally, this project will contribute with its specific analytical tools to several other joint experiments of the research unit.

由于优先流动路径，根和动物洞穴在C输入方面的相关性更大，因此地带C分布和通量的空间异质性远高于表土。因此，消费者和底物的空间隔离更多是一个规则，而不是亚土壤中的例外。作为对观察到的均质化效应和下层土壤缓慢的周转率的解释，这意味着热点相当静态，尽管长时间的底物可用性，但“冷区域”仍然无人居住。根际土壤是一种热点，在其中C输入改变了SOC组成并刺激微生物和酶活性。另一方面，地下土壤中的微生物活性似乎受到养分的限制，如酶活性模式和在第一阶段进行的孵化实验所表明的那样。因此，根际中的新鲜底物输入可以为微生物提供产生这些限制营养素的酶的能量，或者它们可能加剧N-和P-limigition，从而导致根源性有机物在根茎中的积累。该提案中概述的活动的主要目的是调查限制地下土壤SOC降解的因素，从而有助于解决孵化实验中相对较高的矿化速率的矛盾发现，尽管显而易见的14c sib soc显然是14c年龄。消费者和底物之间空间分离的解释机制将通过应用新的成像技术来分析来自各个地点不同深度的不受干扰的土壤样品中的酶活性的空间模式和底物矿化的空间模式。该项目的另一个重点将是微生物活性热点（主要是根际）的表征，这些酶模式和因子刺激或限制了这些微地点相对于散装土壤的矿物质矿化过程。通过确定这些根际效应及其空间延伸，将提供COMISSION模型（PC）根际模块的重要输入参数。长期孵化实验中对14CO2的分析将显示，如果仅最近的SOC输入被矿化或在这些条件下“旧的” SOC不稳定。我们将分析在Grinderwald天文台收集的土壤溶液中的酶活性，以确定其易位到地下土壤中。最后，该项目将以其特定的分析工具为研究部门的其他几个联合实验做出贡献。