Contribution of ectomycorrhizal fungi to the formation and mobilization of soil organic matter (SOM)

在森林生态系统中，外生菌根真菌负责从土壤有机质(SOM)中动员矿质养分，从而显着提高其共生宿主植物的生产力。作为回报，真菌从这些植物中获得大量的光合作用产物，从而形成一个广泛的菌丝系统。这些菌丝构成了土壤生物量的主要部分，并最终成为土壤有机质形成的主要来源。虽然植物与真菌之间的养分交换已经被广泛分析，但这一建议主要集中在真菌对土壤有机质形成的贡献以及真菌获得养分的过程。这两个过程将在土壤生物反应器中使用同位素标记进行单独和定量的研究。对~(13)C标记的真菌物质(双色漆树)在土壤生物反应器中的去向进行分析，可以看出菌丝生物量的不同部分转化为无生命的SOM的速度和程度。作为从真菌菌丝形成SOM的潜在分子或结构标记，我们将使用扫描电子显微镜分析SOM中真菌菌丝的特征残留物，使用PCR方法分析真菌rRNA内转录间隔区的DNA片段，以及脂肪酸和麦角甾醇等生化标记。樟子松试管苗支持的外生菌根菌丝体对13C和15N标记的SOM以及对微生物生物量的影响将在单独的土壤生物反应器实验中进行分析。

In forest ecosystems ectomycorrhizal fungi are responsible for the mobilization of mineral nutrients from soil organic matter (SOM) resulting in a marked increase in productivity of their symbiotic host plants. In return the fungi obtain a significant amount of photosynthetic products from these plants, allowing the formation of an extensive hyphal system. These hyphae constitute a major part of soil biomass and, ultimately, a major source for SOM formation. While plant-fungal nutrient exchange has been analyzed extensively, this proposal is focused on the fungal contribution to SOM formation and on the processes leading to the acquisition of nutrients by the fungi. These two processes will be studied separately and in a quantitative way using isotopic labeling in soil bioreactors. Analysis of the fate of 13C labeled fungal material (Laccaria bicolor) in soil bioreactors will tell how fast and to what extent the various fractions of hyphal biomass are transformed into non-living SOM. As potential molecular or structural markers for SOM formation from fungal hyphae we will analyze characteristic remnants of fungal hyphae in SOM using scanning electron microscopy, DNAfragments using a PCR approach for the fungal rRNA internal transcribed spacerregions and biochemical markers like fatty acids and ergosterol. The impact of ectomycorrhizal mycelia supported by Pinus sylvestris plantlets on 13C- and 15N-labeled SOM and on microbial biomass will be analyzed in separate soil bioreactor experiments.