西南亚高山针叶林外生菌根-土壤N转化的生态学机制及其对气候变暖与氮沉降的响应

Mycorrhiza acts as the linkage between plant and soil, and plays important roles in soil N cycle. However, the effect of mycorrhiza on soil N transformation has been ignored. Up to now, only limited effort has been made to link ectomycorrhiza with N transformation under serious climate warming and nitrogen deposition. Therefore, Picea asperata and Abies faxoniana (the key species of southwest subalpine conifersous forest) are chosen as the study objects in this project. We examine functional microbial community, activities of key enzymes, transformation rate and the composition of soil N pools by potted inoculation experiment, in order to reveal the effect and potential mechanism of ectomycorrhiza on key steps of N transformation. On this basis, the effect of climate change on ectomycorrhiza and its mediated N transformation are investigated by a field artificial warming and nitrogen addition experiment. The aims of this study are: (1) to examine how the effects of ectomycorrhiza on N transformation; (2) to reveal the influences of warming and nitrogen addition on ectomycorrhiza; (3) to identify the potential effects of ectomycorrhiza on soil N transformation under climate warming. This project will be valuable for providing a more comprehensive view of belowground ecological processes under global climate change.

针对当前外生菌根对土壤N转化过程的影响一直被忽视，以及气候变暖与氮沉降日趋严重的现状，本项目选择西南亚高山针叶林建群种粗枝云杉（Picea asperata）和岷江冷杉（Abies faxoniana）为研究对象，先采用盆栽接种实验，通过比较分析土壤N过程关键功能微生物群落特征、土壤酶活性，及转化速率与N库组分变化，揭示外生菌根对土壤N转化关键过程的影响及生态学机制，并在此基础上，通过模拟增温及施氮的控制实验，分析气候变化对外生菌根及其介导的土壤N转化关键过程的潜在影响，试图：1）阐明外生菌根对土壤N转化关键过程的影响机制；2）揭示气候变化对外生菌根侵染、生长及群落组成的影响；3）探讨气候变化对外生菌根-土壤N素转化生态学机制的影响。本项目的实施可为气候变化对典型森林生态系统地下过程的影响提供新的、全面的认识.

针对当前外生菌根对土壤N转化过程的影响一直被忽视，以及全球环境变化日趋严重的现状，本项目选择西南亚高山针叶林建群种为研究对象，采用控制实验，通过比较分析不同处理土壤N过程关键功能微生物群落特征、土壤酶活性，及转化速率与N库组分变化，揭示外生菌根对土壤N转化关键过程的影响及生态学机制，并分析气候变化对外生菌根及其介导的土壤N转化关键过程的潜在影响。研究结果显示：1）外生菌根作为川西亚高山针叶林主要建群种云杉根系的重要组成部分，根际和外延菌丝际土壤微生物群落及N转化关键功能微生物群落结构相似，外延菌丝际关键土壤酶活性、N硝化与矿化速率及N有效性略低于根际土壤但均显著高于C管对照土壤，这说明植物可通过外延菌丝明显影响土壤 N转化过程。2）虽然增温后菌根侵染率显著降低，但R管与H管ECMf含量无显著差异但仍显著高于C管对照土壤，且增温后H与R管N转化关键土壤酶活性及矿化速率均有不同程度提高，而增温对C管N转化关键土壤酶及硝化、矿化速率等无显著影响，因此未来气候变暖背景下川西亚高山针叶林云杉根系及外延菌丝对土壤N转化过程调控具有同等重要的作用。