Mycelia-derived C contributes more to nitrogen cycling than root-derived C in ectomycorrhizal alpine forests

1. Plant roots and their associated microbial symbionts impact carbon (C) and nutrient cycling in ecosystems, but estimates of the relative contributions of root- versus microbe-derived dynamic inputs are highly uncertain. Roots release C into soil via exudation and turnover (i.e., root-derived C), but also by allocating C to mycorrhizal fungal mycelia, which exude C and undergo turnover (i.e., mycelia-derived C). Given that the relative contributions of root- and mycelia-derived C inputs are unknown, a key knowledge gap lies in understanding not only the relative contributions of root- versus mycelia-derived C inputs, but also the consequences of these fluxes on nutrient cycling.
2. Using ingrowth cores and stable isotope analyses, we quantified root- and mycelia-derived C inputs into the soil and their relative contributions to nitrogen (N) cycling in two ectomycorrhizal alpine forests, a 70-year-old spruce plantation and a 200-year-old spruce-fir dominated forest, in western Sichuan...

1. 植物根系及其共生微生物可影响生态系统中的碳（C）与养分循环过程，但当前对根系与微生物来源的动态碳输入相对贡献的估算仍存在极大不确定性。植物根系可通过分泌碳化物与组织周转（即根系来源碳）的途径向土壤输入碳，同时还会将碳分配至菌根真菌菌丝体，由菌丝体通过自身分泌物释放与组织周转的方式输入碳（即菌丝体来源碳）。鉴于目前尚不明确根系与菌丝体来源的碳输入相对占比，当前研究的核心知识空白不仅在于厘清二者的碳输入相对贡献，还需阐明这些碳通量对养分循环的影响效应。
2. 本研究采用根系生长芯（ingrowth core）培养法与稳定同位素分析技术，对川西地区两片外生菌根型高山森林——70年生云杉人工林与200年生以云杉冷杉为优势种的森林——的土壤碳输入来源（根系与菌丝体来源碳）及其对氮（N）循环的相对贡献进行了定量分析……