亚热带林木光合作用新产生的碳是驱动土壤微生物呼吸的关键因子？

森林土壤微生物呼吸主要受环境因子、呼吸底物和土壤生物等因素影响。前期研究表明，亚热带森林土壤微生物可能优先利用光合作用新产生的碳作为底物，但这一过程仍有待验证而且其微生物机制尚不明确。本项目拟以中亚热带常绿阔叶天然林为研究对象，通过野外挖壕沟法和移地重填法相结合，运用土壤CO2高频观测系统和时间序列分析技术手段，阐述光合作用新产生的碳在不同时间尺度上对土壤微生物呼吸的贡献；以添加相同质量、数量的模拟光合作用新产生的碳（13C葡萄糖）和相同质量、不同数量的新碳至不同有机碳含量梯度的土壤，结合DNA-SIP技术，探讨土壤微生物呼吸对输入不同数量的新碳响应，并明确利用植物光合新产生碳的主要贡献微生物类群；通过植物幼苗种植在C4土壤中，揭示植物光合新产生的碳进入土壤后的去向。本项实施目有助于揭示植物光合新产生的碳如何驱动亚热带森林土壤微生物呼吸及其关键的调控因子，同时也有利于完善森林碳循环模型。

Microbial respiration in forest soils is mainly affected by environmental factors (e.g. temperature and moisture), substrates, and soil biota. Previous studies have shown that soil microorganisms may preferentially use newly photosynthetic carbon as a substrate in subtropical forest, but this process remains to be verified and its microbial mechanism is not clearly. The present proposal, firstly, is going to elucidate the contribution of photosynthetic carbon to soil microbial respiration in various time scales in an evergreen broad-leaved forest in mid-subtropics, by using the high-frequency automated soil CO2 flux system combined with soil trenched and relocated method in the field, in the meantime, adopting time-series analysis techniques. Secondly, by adding different amounts of simulated plant photosynthetic carbon (13C glucose) to the soil, the response of soil microbial respiration to the addition of different amounts of carbon is measured, and the microbial groups being responsible for the microbial respiration are identified with DNA-SIP technique. Thirdly, plant seedlings in C4 soil, the fate of newly photosynthetic carbon in the soil will be figured out. The implementation of this proposal will help to reveal how the newly photosynthetic carbon produced by plants drives the microbial respiration in subtropical forest soils and their regulatory mechanisms. Furthermore, the result is conducive to improve the forest carbon cycling model.