Linking land use intensity, biodiversity, soil microbial processes and organo-mineral interactions for a mechanistic understanding of Nitrogen turnover in grassland ecosystems (BE_BioMON)

将土地利用强度、生物多样性、土壤微生物过程和有机矿物相互作用联系起来，从机制上理解草原生态系统的氮周转 (BE_BioMON)

• 批准号: 512359828
• 负责人: Privatdozent Dr. Michael Dannenmann
• 金额: --
• 依托单位: Abteilung Vergleichende Mikrobiomanalysen (COMI)
• 依托单位国家: 德国
• 项目类别: Infrastructure Priority Programmes
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/512359828?language=en
• 关键词: Linking; land; use; intensity; biodiversity

Increase in land use intensity (LUI) is a strong driver for environmental nitrogen (N) losses and decline of biodiversity and multifunctionality in grassland ecosystems. Still, interactions between LUI, above- and belowground biodiversity and N cycling in grassland ecosystems lack a mechanistic understanding, which prevents targeted mitigation measures. Through an interdisciplinary integration of soil microbial ecology, short-term processes of biotic N partitioning in the plant-soil-microbe system, and long-term physicochemical soil organic nitrogen (SON) retention pathways, BE_BioMon aims to fill this knowledge gap by linking measurements and modelling. We hypothesize that with decreasing LUI and more diverse microbiome, N partitioning shifts from nitrification/denitrification to biotic assimilation. This promotes N retention via necromass stabilization in particulate and mineral-associated SON depending on aggregate turnover and microscale soil architecture. Furthermore, we expect that increasing LUI will result in a shift from symbiotic to associative N fixation, which will increase the N2:N2O emission ratio due to truncated denitrification pathways in symbiotic diazotrophs. Moreover, we hypothesize that soil δ15N is fingerprinting LUI effects on N cycling, and thus can serve as a process integrating benchmark quantity for ecosystem models. This is expected to advance modeling-based spatiotemporal scaling of LUI effects on grassland N cycling. To test the hypotheses, we will perform field 15N fertilizer tracing experiments at selected plots of different LUI at all 3 Biodiversity Exploratories (BE) (WP1). In WP2, we will conduct mesocosm experiments with 15N2 exposure to disentangle LUI effects on the fates of BNF-N. WP3 is designed to fingerprint N cycling within the BE soil sampling campaign at all grassland EPs through vertical δ15N soil profiles, metagenomics, and SON fractionation. The gained knowledge from experimental work of WP1-3 and already available BExIS data will be used for testing and advancing N routines of the process-based ecosystem model LandscapeDNDC. This model, expanded by a dynamic vegetation model CoSMo, is used to evaluate differences in N cycling across the entirety of BE grassland plots (WP4). In WP5 (synthesis) we will mechanistically link effects of LUI and biodiversity with measured and modeled biogeochemical N transformations, N retention through organo-mineral interactions and full N balances at scales from days to years. We expect that this synthesis finally allows for an advanced mechanistic and functional understanding of ecosystem N cycling as influenced by LUI, above- and belowground biodiversity and site-specific properties.

土地利用强度(LUI)的增加是草原生态系统环境氮损失、生物多样性和多功能下降的重要驱动因素。尽管如此，草原生态系统中LUI、地上和地下生物多样性与N循环之间的相互作用缺乏机械性的理解，这阻碍了有针对性的缓解措施。通过对土壤微生物生态学、植物-土壤-微生物系统中生物氮分配的短期过程和长期土壤有机氮(SON)保留途径的跨学科集成，BE_BioMon旨在通过将测量和建模联系起来来填补这一知识空白。我们假设，随着LUI的降低和微生物群落的多样化，N的分配从硝化/反硝化转变为生物同化。这取决于团聚体周转和微尺度土壤结构，通过在颗粒物和矿物质伴生的SON中通过坏死体稳定来促进N的保留。此外，我们预计增加的LUI将导致从共生固氮向缔合固氮的转变，这将由于共生重氮菌的反硝化途径被截断而增加N_2：N_2O排放比。此外，我们假设土壤δ15N是对氮素循环的Lui效应的指纹图，因此可以作为生态系统模型的基准量的整合过程。这有望推进基于模型的草地N循环LUI效应的时空尺度研究。为了验证假设，我们将在所有3个生物多样性探索室(WP1)的不同LUI的选定地块进行田间15N肥料示踪实验。在WP2中，我们将在15N2暴露的情况下进行介体实验，以解开LuI对BNF-N命运的影响。WP3旨在通过垂直δ15N土壤剖面、后基因组学和SON分级，在所有草原EP的BE土壤采样活动中识别N循环。从WP1-3的实验工作中获得的知识和已有的BExIS数据将用于测试和推进基于过程的生态系统模型Landscape DNDC的N个例程。该模型是在动态植被模型COSMO的基础上扩展而来的，被用来评估整个BE草原样地(WP4)的N循环差异。在WP5(合成)中，我们将从机械上将LUI和生物多样性的影响与测量和模拟的生物地球化学N转化、通过有机-矿物相互作用的N保持以及从几天到几年的尺度上的全N平衡联系起来。我们期望，这一综合最终允许对生态系统N循环的机制和功能有一个更高级的理解，即受LUI、地上和地下生物多样性和特定地点属性的影响。