森林粗木质残体分解研究进展

Review on the study of forest coarse woody debris decomposition

森林粗木质残体主要包括倒木、枯立木、大枯枝、树桩和粗根等,它们是绝大多数森林生态系统的结构性成分,在全球碳循环和生物多样性保育等方面发挥着不可替代的作用。特别是近些年,极端高温、干旱、热带气旋等极端气候事件正在加速树木死亡,改变森林粗木质残体形成的方式和分解过程,森林生态系统功能和稳定性也会受到深刻影响,生态学家对此也越来越重视。如今,生态学家通过野外观测和控制实验,围绕粗木质残体的分解特征、调控机制和分解过程中粗木质残体上的生物多样性开展了大量研究,促进了粗木质残体生态学的快速发展。该文首先汇总了最常见的用于森林粗木质残体分解过程的研究方法,并且描述了各研究方法适用的情景。其次,从形态、物理和化学性状方面探讨了粗木质残体的分解特征。然后,围绕着影响森林粗木质残体分解的控制因素,系统梳理和总结了已取得的研究结果。具体来说,粗木质残体分解主要受到基质质量、分解者和环境条件的调控,其中基质质量和分解者在样点尺度上影响着分解过程,基质质量对分解者群落有自下而上的调控作用,环境条件在区域或更大研究尺度上发挥主导作用。粗木质残体在分解的同时孕育了数量巨大、种类丰富的生物,主要类群包括苔藓类附生植物、细菌、真菌和无脊椎动物。无脊椎动物对森林粗木质残体的利用方式最为复杂,可能将其作为栖息地、掩蔽所、繁殖地、取食场所。附生植物的演替过程与分解时间正相关,但与腐烂程度联系不紧密,其他生物类群的演替则更多地受到基质质量的影响。由于以往的综述鲜有涉及不同结构组分(树皮和木质部)分解的研究进展,该文补充和探讨了树皮和木质部的分解特征和潜在的相互作用过程。由于粗木质残体分解缓慢的特点和研究方法的限制,目前许多机理的相关研究仍不够深入,该文围绕粗木质残体分解机制和生物多样性保育功能探讨了未来需要重点关注的研究内容及可能的研究方法。

Coarse woody debris(CWD)consists mainly of log,snag,large branch,stump and coarse root.CWD is widely distributed on the forest floor and especially valuable in most of forest ecosystems because it is vital to the global carbon cycling and biodiversity conservation.In particular,increasingly extreme climatic events,such as persistent high temperature,prolonged drought,and tropical cyclones are greatly affecting forest ecosystem function and stability by accelerating tree death,changing the sources of CWD inputs and decomposition processes.Thus,research about CWD decomposition has becoming an ecological hotspot.More and more ecologists have contributed greatly in disentangling the mechanisms on how factors control decomposition process and how CWD nurses biodiversity,which have greatly stimulated the development of CWD ecology.In this review,firstly,we summarized the dominant methodology used in the CWD decomposition study.Then we introduced the scenarios which could be applied for each method.Secondly,we described the morphological,physical and chemical properties of CWD during decomposition,respectively.Thirdly,we overviewed previous studies disentangling factors affecting decomposition dynamics.Briefly,substrate quality,decomposer community and environmental conditions are the main control factors of CWD decomposition.Substrate quality and decomposer community dominate the CWD decomposition process at site scale,with substrate quality regulating the decomposer community with bottom-up effects,while environmental conditions functioning at regional or broad scales.Fourthly,huge amount and diverse types of organisms use decaying CWD as a habitat,many of which are endangered species.It is fundamental to maintain the biodiversity in the CWD ecosystem.Epixylic plants(especially for bryophytes),bacteria,fungi and invertebrates are the common species living on/in the CWD.Invertebrates can utilize CWD in different ways,such as habitat,nourishment and foraging sites,which are species specific.The community composition changed along with decomposition process.The succession of epixylic plants is correlated with the duration of decomposition,while the succession of other types of organisms is mainly driven by the changing substrate quality of decaying CWD.Additionally,we summarized the decomposition dynamics of different structural components(bark vs.xylem)and the interaction between bark and xylem during CWD decomposition which have been overlooked.Finally,as the long decomposition time and the limitation of methodology impeded the progress of revealing the mechanism of CWD decomposition,we made an outlook of future research in the area of decomposition mechanism and biodiversity conservation,and provided methodology that could be of help in stimulating the further development in CWD ecology.