细根分解研究及其存在的问题

Advances in Studying Fine Root Decomposition in Forests

细根分解是陆地生态系统C和养分循环的重要环节。主要包括淋溶和破碎等物理过程和以生物作用为主的化学过程。这些过程受复杂的细根化学成分及外部土壤因子的综合控制,如细根本身养分含量、木质素和纤维素含量、土壤温度、水分、养分的有效性以及土壤动物、真菌和细菌等。但是,细根分解发生在不能直接观测的地下部分,人为改变细根分解的自然环境是研究过程中存在的主要问题。埋袋法虽然应用最为普遍,但是它严重地干扰了细根分解环境,导致低估分解速率。最近提出的原状土芯法(intact-core)克服了埋袋法的主要缺陷,是目前细根分解研究中最接近自然分解过程的研究方法,但也存在一些问题。因此,如何设计有效且能够真实的反映细根自然分解过程的试验方法是今后该领域研究最重要和最具挑战性的课题。

Decomposition of fine roots is one of the major pathways of carbon and nutrient cycling in terrestrial ecosystems. There are three general processes in fine-root decomposition: leaching, frag- mentation and chemical alteration, which are controlled by substrate quality such as soluble nutrient concentrations, lignin, and cellulose; soil conditions such as temperature, moisture, and nutrient availability; and animals, fungi and bacteria in soil. The main question for research in fine-root decom- position in terms of buried litterbags is whether the natural decay conditions of fine roots are altered due to destructive sampling, washing and removing soil particles. The technique of buried litterbags is commonly used worldwide in fine-root decomposition research, and its disadvantages are that the physical and biological microenvironments around the fine roots are greatly disturbed, which results in an underestimated decomposition rate. Recently, crop and forest studies have involved an intact- core technique, which closely mimics in situ decay conditions. Compared with decay-rate estimations with the buried litterbag approach, those with the intact-core technique are the most effective for fine- root decay. However, the most important and challenging issues in study of fine-root decomposition are to design an efficient experiment and develop new techniques. ①国家自然科学基金重点项目(30130160)资助。