地上枯落物的累积、分解及其在陆地生态系统中的作用

了解陆地生态系统地上枯落物的累积和分解过程对认识它的生态作用、通过管理地上枯落物调控陆地生态系统功能和服务有重要意义。综述了陆地生态系统地上枯落物的积累和分解过程及其影响因素,然后概括了通过这些过程地上枯落物所发挥的生态作用,最后,在全球变化背景下,基于当前研究进展提出陆地生态系统地上枯落物研究的前景。地上枯落物累积在时间尺度上一般遵循植物的生命周期,同时也受环境因子的调控。大的空间尺度上,枯落物累积主要受水热因子控制,伴随植被类型的变化,表现随纬度升高而减少的趋势。然而,在局域尺度内,枯落物累积除受水、热因子限制,还被群落结构、土壤条件、植食动物等因素影响,表现较大变异性。当前,人类干扰作为一个不可忽视的因素,正在强烈甚至不可逆转的改变地表植被覆盖和枯落物累积。地上枯落物的分解过程包括淋溶、光降解、土壤动物和微生物分解,这些过程同时进行并相互影响。尽管目前还不清楚,但区分这些分解过程和分解产物的去向对了解陆地生态系统物质循环有重要意义。枯落物分解首先被自身类型、化学组成、物种多样性决定,同时也受分解者群体、非生物环境影响。其中,枯落物分解与其化学特性、物种多样性及土壤养分状况的关系是研究的热点,也是广泛争议的焦点。通过累积和分解,地上枯落物对陆地生态系统有物理、化学、生物作用。目前,枯落物的物理和化学作用研究较为透彻,而由于受枯落物数量、环境条件、响应植物特征或一些有待挖掘的未知因素的共同限制,地上枯落物的生物作用,尤其对植物的作用在不同研究中仍没有达成普遍的共识。全球变化可能影响地上枯落物累积、分解和生态作用。在全球变化的背景,研究地上枯落物产量和性状变化、阐明枯落物分解的分室模型、继续分析枯落物性状和分解关系、深入揭示枯落物的生态作用及其制约因素,理解和预测地上枯落物数量和质量变化对陆地生态系统功能和服务的影响是必要的。

The accumulation, decomposition and ecological effects of above-ground litter in terrestrial ecosystem

Understanding of the accumulation and decomposition processes of above-ground litter is of importance for us to study its ecological function and service in terrestrial ecosystems. The current paper first reviews the accumulation and decomposition processes of above-ground litter in terrestrial ecosystem and factors that affect these two ecological processes, then summarizes the ecological effects of above-ground litter in terrestrial ecosystem as a result of its accumulation and decomposition. Finally, under the view of global climate change, based on previous research progress, we review the perspectives of research on above-ground litter in terrestrial ecosystem. On the temporal scale, the accumulation of above-ground litter commonly follows the plant life cycle, and it is also regulated by environment factors, such as climatic conditions, soil temperature and moisture. On the large spatial scale, the accumulation of above-ground litter is primarily controlled by hydrothermal factors, resulting in the change in vegetation type, which show a decreased trend with the elevated latitude. However, on the local scale, apart from the constraints of hydrothermal factors, the accumulation of above-ground litter are also impacted by community structure, soil conditions, activities of herbivores, which shows more variability. Human disturbance is also an important factor that induces change of terrestrial vegetation cover and litter accumulation, and in many cases the changes are even irreversible. The decomposition processes of above-ground litter in terrestrial ecosystem include leaching, photo-degradation, soil animal and microbial decomposition. These decomposition processes occur simultaneously and interactively. Although still it is not well known now, distinguishing these decomposition process and fate of decomposition products with them are of importance for understanding the nutrient recycle in terrestrial ecosystem. Litter decomposition firstly is determined by its type, chemical composition, species diversity, but also affected by decomposer community and abiotic environment factors. Among these factors, the relationships between decomposition and litter chemical traits, species diversity and soil nutrient status are the key focus of this study. Through its accumulation and decomposition, above-ground litter has significant effects on terrestrial ecosystem physically, chemically and biologically. Currently, there are ample studies on the physical and chemical properties of above-ground litters, but there are very few studies on the biological property of above-ground litter, especially for the effects above-ground litters on vegetation that are still controversial as they are limited by complicated factors, including litter quantity, environment condition, the traits from impacted plants, even some unknown factors by now. Global climate change may change the accumulation and decomposition of above-ground litter and their ecological effects on the distribution, growth and traits of terrestrial plants in terrestrial ecosystem, through changes of climate and soil conditions. Under the global climate change, it is necessary to study the litter production and trait change on the spatial scales, expound the compartment model of litter decomposition on the temporal and spatial scales, deeply analyze the relationships between above-ground litter traits and decomposition, and further reveal the ecological effects of above-ground litter when relative limited factors are integrated into analysis, understand and predict the impact of above-ground litter on terrestrial ecosystem function and service under the scenario of the future environment change.