中文摘要：

植物根系分解是驱动陆地生态系统碳和养分循环的关键过程之一。直径小于2 mm的根是一个复杂的异质性细根系统。位于细根系统末端的低级根（如1~3级根）或直径较小的细根（如直径小于0.5 mm的细根）,执行水分和养分吸收功能,其周转迅速（0.5~2.5次/a）,是植物根系向土壤输入碳和养分的主要途径。近年来对细根分解的研究表明,在细根系统中,低级根的分解速率显著慢于高级根（如3级以上的根）或直径较大的细根（如直径大于0.5 mm的细根）,执行输导和储藏功能。本文综述了影响细根异速分解的3个可能途径：菌根、碳质量和氮含量,旨在增强研究者对全球变化下细根功能属性（如细根直径）如何影响生态系统碳和养分循环的理解。

英文摘要：

Plant root decomposition is one of the critical processes of carbon and nutrient cycling in terrestrial ecosystems. Plant roots less than 2 mm in diameter constitute a heterogeneous branching system. Within the system,lower order roots（ e. g. 1st-3rdorder） or fine roots in smaller diameter（ e. g. less than 0. 5mm in diameter） which mainly serve for water and nutrient uptake have fast turnover rates（ 0. 5-2. 5times per year）,and contribute greatly to soil carbon and nutrients pools. Recently,increasing number of studies have shown that lower order roots decompose more slowly than higher order roots（ e. g. more than 3rdorder） or fine roots in larger diameter（ e. g. more than 0. 5 mm in diameter） which mainly serve for water-nutrient transport and carbon storage. Here,we review three main factors explaining the contrasting decomposition rates across different root orders or diameter classes： mycorrhizal,carbon quality and nitrogen content. Overall,we intend to provide insights into the important roles of functional traits（ e. g. diameter） of fine roots that play in ecosystem carbon and nutrient cycling in a changing world.