外源氮输入增加与植物入侵对盐沼碳循环关键过程的影响及其机理

Increased input of exogenous nitrogen and plant invasion pose serious threats to global and China's environments, especially in sensitive ecosystems such as saltmarsh. Previous studies showed that increased input of exogenous nitrogen can promote expansion of invasive plants, potentially leading to intensified impacts of plant invasion on native ecosystem processes. However, the reasons and intensities of the potential impacts remain to be further studied. In the Yangtze River Estuary as the research site and with an exotic plant Spartina alterniflora widely invaded in China saltmarsh and a native plant Phragmites australis as the research materials, this project through a field control experiment will compare differences in input (photosynthetic rate, productivity, etc.), distribution (soil carbon and its fractions, etc.), and stability (soil respiration, functional microbial community and activity, etc.) of ecosystem carbon processes at the different stages of replacement of the native plant by the invasive plant, with and without N addition. This project will reveal the effects of plant invasion on the ecosystem carbon cycling and their mechanisms under the global background of increased nitrogen level. This project will promote our understanding of carbon cycle under joint influences of increased input of exogenous nitrogen and plant invasion, and provide theoretical reference for the prediction of carbon processes in the context of global change.

外源氮输入增加与植物入侵对全球及我国生态环境构成了严重威胁，尤其体现在盐沼等敏感生态系统中。研究表明，外源氮输入增加可促进植物入侵，从而潜在加剧植物入侵对土著生态系统过程的影响。然而，目前对这一影响的潜在成因与强度还有待进一步深入探讨。本项目以长江口盐沼为研究地点，以广泛入侵我国盐沼的外来植物互花米草以及土著植物芦苇为研究材料，通过野外控制实验，比较在施氮与未施氮处理下该入侵植物取代土著植物不同阶段盐沼碳的输入（光合效率、生产力等）、分配（土壤碳及其组分等）、稳定性（土壤呼吸、功能微生物群落及其活性等）等差异，揭示全球氮素水平普遍升高背景下植物入侵对生态系统碳循环的影响及其机理。开展此项研究，将促进对外源氮输入增加和植物入侵共同影响下敏感生态系统碳循环的了解，为预测全球变化背景下生态系统的碳过程提供理论参考。

外源氮输入增加和植物入侵对全球及我国生态环境构成了严重威胁，尤其体现在盐沼等敏感生态系统中。研究表明，外源氮输入增加可促进植物入侵，从而潜在加剧植物入侵对土著生态系统过程的影响。然而，目前对这一影响的潜在成因与强度还有待进一步深入探讨。为此，本项目在长江口崇明建立了长期野外控制实验，以广泛入侵我国盐沼的外来植物互花米草以及土著植物芦苇为研究材料，比较在施氮和未施氮处理下该入侵植物取代土著植物不同阶段盐沼碳的输入、分配、稳定性等差异。我通过了4年的研究取得了以下主要进展：1）发现了外源氮施加对互花米草生产力的促进远大于芦苇，并且对互花米草生长速率起到主要调控作用；2）发现了互花米草根系性状具有较高响应外源氮的能力，从而影响植物生产力与地下微生物群落；3）发现了外源氮施加可促进互花米草甲烷气体排放，并揭示了这一过程的微生物机制。通过该项目的实施进一步揭示全球氮素水平普遍升高背景下植物入侵对生态系统碳循环的影响及其机理，促进了对外源氮输入增加和植物入侵共同影响下敏感生态系统碳循环的了解，为预测全球变化背景下生态系统的碳过程提供理论参考。项目按照计划任务书执行，发表了14篇论文，其中SCI论文13篇。